5,265 research outputs found
Maximally localized Wannier functions in LaMnO3 within PBE+U, hybrid functionals, and partially self-consistent GW: an efficient route to construct ab-initio tight-binding parameters for e_g perovskites
Using the newly developed VASP2WANNIER90 interface we have constructed
maximally localized Wannier functions (MLWFs) for the e_g states of the
prototypical Jahn-Teller magnetic perovskite LaMnO3 at different levels of
approximation for the exchange-correlation kernel. These include conventional
density functional theory (DFT) with and without additional on-site Hubbard U
term, hybrid-DFT, and partially self-consistent GW. By suitably mapping the
MLWFs onto an effective e_g tight-binding (TB) Hamiltonian we have computed a
complete set of TB parameters which should serve as guidance for more elaborate
treatments of correlation effects in effective Hamiltonian-based approaches.
The method-dependent changes of the calculated TB parameters and their
interplay with the electron-electron (el-el) interaction term are discussed and
interpreted. We discuss two alternative model parameterizations: one in which
the effects of the el-el interaction are implicitly incorporated in the
otherwise "noninteracting" TB parameters, and a second where we include an
explicit mean-field el-el interaction term in the TB Hamiltonian. Both models
yield a set of tabulated TB parameters which provide the band dispersion in
excellent agreement with the underlying ab initio and MLWF bands.Comment: 30 pages, 7 figure
Distinguishing two-qubit states using local measurements and restricted classical communication
The problem of unambiguous state discrimination consists of determining which
of a set of known quantum states a particular system is in. One is allowed to
fail, but not to make a mistake. The optimal procedure is the one with the
lowest failure probability. This procedure has been extended to bipartite
states where the two parties, Alice and Bob, are allowed to manipulate their
particles locally and communicate classically in order to determine which of
two possible two-particle states they have been given. The failure probability
of this local procedure has been shown to be the same as if the particles were
together in the same location. Here we examine the effect of restricting the
classical communication between the parties, either allowing none or
eliminating the possibility that one party's measurement depends on the result
of the other party's. These issues are studied for two-qubit states, and
optimal procedures are found. In some cases the restrictions cause increases in
the failure probability, but in other cases they do not. Applications of these
procedures, in particular to secret sharing, are discussed.Comment: 18 pages, two figure
A comparative study of super- and highly-deformed bands in the A ~ 60 mass region
Super- and highly-deformed rotational bands in the A ~ 60 mass region are
studied within cranked relativistic mean field theory and the
configuration-dependent shell-correction approach based on the cranked Nilsson
potential. Both approaches describe the experimental data well. Low values of
the dynamic moments of inertia J^(2) compared with the kinematic moments of
inertia J^(1) seen both in experiment and in calculations at high rotational
frequencies indicate the high energy cost to build the states at high spin and
reflect the limited angular momentum content in these configurations.Comment: 11 pages, 4 PostScript figures, Latex, uses 'epsf', submitted to
Phys. Lett.
Improved CRISPR-based suppression gene drives mitigate resistance and impose a large reproductive load on laboratory-contained mosquito populations
Abstract CRISPR-based genes drives bias their own inheritance and can be used to modify entire populations of insect vectors of disease as a novel form of sustainable disease control. Gene drives designed to interfere with female fertility can suppress populations of the mosquito vector of malaria, however laboratory demonstrations showed strong unintended fitness costs and high levels of resistant mutations that limited the potential of the first generation of gene drives to spread. We describe three new gene drives designed to restrict spatio-temporal nuclease expression by using novel regulatory sequences. Two of the three new designs dramatically improve fitness and mitigate the creation and selection of resistance. We dissect the relative contributions of germline CRISPR activity versus embryonic CRISPR activity resulting from parental deposition, showing that the improved performance of the new designs is due to tighter germline restriction of the nuclease activity and significantly lower rates of end-joining repair in the embryo. Moreover, we demonstrate in laboratory-contained population experiments that these gene drives show remarkably improved invasion dynamics compared to the first generation drives, resulting in greater than 90% suppression of the reproductive output and a delay in the emergence of target site resistance, even at a loosely constrained target sequence. These results illustrate important considerations for gene drive design and will help expedite the development of gene drives designed to control malaria transmission in Africa
Pre-galactic metal enrichment - The chemical signatures of the first stars
The emergence of the first sources of light at redshifts of z ~ 10-30
signaled the transition from the simple initial state of the Universe to one of
increasing complexity. We review recent progress in our understanding of the
formation of the first stars and galaxies, starting with cosmological initial
conditions, primordial gas cooling, and subsequent collapse and fragmentation.
We emphasize the important open question of how the pristine gas was enriched
with heavy chemical elements in the wake of the first supernovae. We conclude
by discussing how the chemical abundance patterns conceivably allow us to probe
the properties of the first stars and subsequent stellar generations, and allow
us to test models of early metal enrichment.Comment: 52 pages, 20 figures, clarifications, references added, accepted for
publication in the Reviews of Modern Physic
Quantum Communication between N partners and Bell's inequalities
We consider a family of quantum communication protocols involving
partners. We demonstrate the existence of a link between the security of these
protocols against individual attacks by the eavesdropper, and the violation of
some Bell's inequalities, generalizing the link that was noticed some years ago
for two-partners quantum cryptography. The arguments are independent of the
local hidden variable debate.Comment: 4 pages, 2 figure
A measurement of the differential cross section for the two-body photodisintegration of 3He at theta_LAB = 90deg using tagged photons in the energy range 14 -- 31 MeV
The two-body photodisintegration of 3He has been investigated using tagged
photons with energies from 14 -- 31 MeV at MAX-lab in Lund, Sweden. The
two-body breakup channel was unambiguously identified by the (nonsimultaneous)
detection of both protons and deuterons. This approach was made feasible by the
over-determined kinematic situation afforded by the tagged-photon technique.
Proton- and deuteron-energy spectra were measured using four silicon
surface-barrier detector telescopes located at a laboratory angle of 90deg with
respect to the incident photon-beam direction. Average statistical and
systematic uncertainties of 5.7% and 6.6% in the differential cross section
were obtained for 11 photon-energy bins with an average width of 1.2 MeV. The
results are compared to previous experimental data measured at comparable
photon energies as well as to the results of two recent Faddeev calculations
which employ realistic potential models and take into account three-nucleon
forces and final-state interactions. Both the accuracy and precision of the
present data are improved over the previous measurements. The data are in good
agreement with most of the previous results, and favor the inclusion of
three-nucleon forces in the calculations.Comment: 12 pages, 13 figures; further Referee comments addresse
Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities
Differential cross sections for Compton scattering from the deuteron were
measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at
nominal laboratory angles of , , and . Tagged
photons were scattered from liquid deuterium and detected in three NaI
spectrometers. By comparing the data with theoretical calculations in the
framework of a one-boson-exchange potential model, the sum and difference of
the isospin-averaged nucleon polarizabilities, and (in units of fm),
have been determined. By combining the latter with the global-averaged value
for and using the predictions of the Baldin sum rule for
the sum of the nucleon polarizabilities, we have obtained values for the
neutron electric and magnetic polarizabilities of (total) (model) and (total) (model), respectively.Comment: 4 pages, 2 figures, revtex. The text is substantially revised. The
cross sections are slightly different due to improvements in the analysi
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