1,541 research outputs found
High‐nuclearity mixed‐valence magnetic clusters : A general solution of the double exchange problem
We report here a general solution of the double‐exchange problem in the high‐nuclearity mixed valence systems containing arbitrary number P of the electrons delocalized over the network of N (P<N) localized spins. The developed approach is based on the successive (chainlike) spin‐coupling scheme and takes full advantage from the quantum angular momentum theory. In the framework of this approach the closed‐form analytical expressions are deduced for the matrix elements of the double exchange interaction, two‐electron transfer, and three‐center interaction that can be referred to as the potential exchange transfer. For the arbitrary nuclearity mixed‐valence systems the matrix elements of all named interactions are expressed in terms of all relevant spin quantum numbers and 6j symbols and do not contain higher order recoupling coefficients. We describe also the combined approach taking into account both angular momentum consideration and advantages of point symmetry adapted basis [email protected] , [email protected] ; [email protected] ; [email protected] ; [email protected]
Magnetic exchange interaction in a pair of orbitally degenerate ions: Magnetic anisotropy of [Ti2Cl9]−3
The theory of the kinetic exchange in a pair of orbitally degenerate ions developed by the authors [J. Phys. Chem. A 102, 200 (1998)] is applied to the case of face-shared bioctahedral dimer (overall D3h-symmetry). The effective kinetic exchange Hamiltonian is found for a 2T2–2T2 system taking into account all relevant transfer pathways and charge-transfer crystal field states. The influence of different transfer integrals involved in the kinetic exchange on the energy pattern and magnetic properties of the system is examined. The role of other related interactions (trigonal crystal field, spin–orbit coupling) is also discussed in detail. Using the pseudoangular momentum representation and the technique of the irreducible tensor operators of R3-group we give a general outlook on the nontrivial symmetry properties of the effective Hamiltonian for the D3h-pair, and on the magnetic anisotropy arising from the orbital interactions specific for the case of orbital degeneracy. The magnetic properties of the binuclear unit [Ti2Cl9]−3 in Cs3Ti2Cl9 are discussed with a special emphasis on the magnetic anisotropy experimentally observed in this system. The existing exchange models for [Ti2Cl9]−3 and the concept of the effective Hamiltonian are discussed in the context of the present [email protected] ; [email protected] ; [email protected] ; [email protected]
Calculating the energy spectra of magnetic molecules: application of real- and spin-space symmetries
The determination of the energy spectra of small spin systems as for instance
given by magnetic molecules is a demanding numerical problem. In this work we
review numerical approaches to diagonalize the Heisenberg Hamiltonian that
employ symmetries; in particular we focus on the spin-rotational symmetry SU(2)
in combination with point-group symmetries. With these methods one is able to
block-diagonalize the Hamiltonian and thus to treat spin systems of
unprecedented size. In addition it provides a spectroscopic labeling by
irreducible representations that is helpful when interpreting transitions
induced by Electron Paramagnetic Resonance (EPR), Nuclear Magnetic Resonance
(NMR) or Inelastic Neutron Scattering (INS). It is our aim to provide the
reader with detailed knowledge on how to set up such a diagonalization scheme.Comment: 29 pages, many figure
P and R Wave Detection in Complete Congenital Atrioventricular Block
Complete atrioventricular block (type III AVB) is characterized by an absence of P wave transmission to ventricles. This implies that QRS complexes are generated in an autonomous way and are not coordinated with P waves. This work introduces a new algorithm for the detection of P waves for this type of pathology using non-invasive electrocardiographic surface leads. The proposed algorithm is divided into three stages. In the first stage, the R waves located by a QRS detector are used to generate the RR series and time references for the other stages of the algorithm. In the second stage, the ventricular activity (QT segment) is removed by using an adaptive filter that obtains an averaged pattern of the QT segment. In the third stage, a new P wave detector is applied to the residual signal obtained after QT cancellation in order to detect P wave locations and get the PP time series. Eight Holter records from patients with congenital type III AVB were used to verify the proposed algorithm. Although further improvements should be made to improve the algorithm¿s performance, the results obtained show high average values of sensitivity (90.52 %) and positive prediction (90.98%)
Short-term changes in left and right systolic function following ferric carboxymaltose : a substudy of the Myocardial-IRON trial
Funding: This work was supported in part by an unrestricted grant from Vifor Pharma and Proyectos de Investigación de la Sección de Insuficiencia Cardiaca 2017 from Sociedad Española de Cardiología.The mechanisms underlying the beneficial effect of ferric carboxymaltose (FCM) in patients with heart failure (HF) and iron deficiency (ID) have not been completely characterized. The Myocardial-IRON trial was a double-blind, randomized trial that evaluated myocardial iron repletion following FCM vs. placebo in 53 patients with HF and ID. In this post hoc analysis, we evaluated whether treatment with FCM was associated with cardiac magnetic resonance changes in left and right ventricular function (LVEF and RVEF, respectively) at different points of systolic dysfunction. We included patients from the Myocardial-IRON trial with left and right ventricular systolic dysfunction (LVSD and RVSD, respectively) at enrolment. Linear mixed regression models were used to evaluate changes at 7 and 30 days on LVEF and RVEF at cardiac magnetic resonance. At enrolment, 27 (50.9%) and 38 (71.7%) patients had LVEF < 40% (LVSD) or <45% (LVSD), respectively, and 10 (18.9%) and 17 (32.1%) patients had RVEF < 45% (RVSD) or <51% in women and <52% in men (RVSD, respectively. Treatment with FCM was associated with a significant improvement in LVEF at 30 days (LVSD: Δ2.3%, P < 0.001; LVSD: Δ4.1, P = 0.014). FCM was also associated with a significant and early improvement in RVEF at 7 days (RVSD: Δ6.9%, P = 0.003; RVSD: Δ3.2%, P = 0.003) that persisted at 30 days (RVSD: Δ8.1%, P < 0.001; RVSD: Δ4.7%, P < 0.001). In patients with HF and systolic dysfunction with ID, FCM was associated with short-term improvement in LVEF and, especially, in RVEF
EU-wide methodology to map and assess ecosystem condition
The EU Biodiversity Strategy for 2030 calls for developing an EU-wide methodology to map, assess and achieve good condition of ecosystems, so they can deliver benefits to society through the provision of ecosystem services. The EU-wide methodology presented in this report addresses this methodological gap.
The EU-wide methodology has adopted the System of Environmental Economic Accounting - Ecosystem Accounting (SEEA EA) as reference framework. The SEEA EA is an integrated framework for organizing biophysical information about ecosystems, adopted as a global statistical standard by the United Nations. The SEEA EA is also the reference framework under the proposal for the amendment of Regulation (EU) No 691/2011 on European environmental economic accounts.
Building on previous work done within the MAES initiative, the EU-wide methodology presents useful insights to operationalise the SEEA EA at EU level by integrating different EU data streams in a consistent way with this global statistical standard to consistently map and assess ecosystem condition in the EU across all ecosystem types. The adoption of the SEEA EA framework offers the flexibility to integrate different data flows, leveraging the use of available EU data, such as data reported by MS under EU legislation and EU geospatial data. The EU-wide methodology.
The implementation of the EU-wide methodology, making use of available data, will provide the scientific knowledge base to support a range of policies and legal instruments
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
Search for the standard model Higgs boson decaying to a bb pair in events with one charged lepton and large missing transverse energy using the full CDF data set
We present a search for the standard model Higgs boson produced in
association with a W boson in sqrt(s) = 1.96 TeV p-pbar collision data
collected with the CDF II detector at the Tevatron corresponding to an
integrated luminosity of 9.45 fb-1. In events consistent with the decay of the
Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a
neutrino, we set 95% credibility level upper limits on the WH production cross
section times the H->bb branching ratio as a function of Higgs boson mass. At a
Higgs boson mass of 125 GeV/c2 we observe (expect) a limit of 4.9 (2.8) times
the standard model value.Comment: Submitted to Phys. Rev. Lett (v2 contains clarifications suggested by
PRL
Search for the standard model Higgs boson decaying to a pair in events with no charged leptons and large missing transverse energy using the full CDF data set
We report on a search for the standard model Higgs boson produced in
association with a vector boson in the full data set of proton-antiproton
collisions at TeV recorded by the CDF II detector at the
Tevatron, corresponding to an integrated luminosity of 9.45 fb. We
consider events having no identified charged lepton, a transverse energy
imbalance, and two or three jets, of which at least one is consistent with
originating from the decay of a quark. We place 95% credibility level upper
limits on the production cross section times standard model branching fraction
for several mass hypotheses between 90 and . For a Higgs
boson mass of , the observed (expected) limit is 6.7
(3.6) times the standard model prediction.Comment: Accepted by Phys. Rev. Let
Search for the standard model Higgs boson decaying to a bb pair in events with two oppositely-charged leptons using the full CDF data set
We present a search for the standard model Higgs boson produced in
association with a Z boson in data collected with the CDF II detector at the
Tevatron, corresponding to an integrated luminosity of 9.45/fb. In events
consistent with the decay of the Higgs boson to a bottom-quark pair and the Z
boson to electron or muon pairs, we set 95% credibility level upper limits on
the ZH production cross section times the H -> bb branching ratio as a function
of Higgs boson mass. At a Higgs boson mass of 125 GeV/c^2 we observe (expect) a
limit of 7.1 (3.9) times the standard model value.Comment: To be submitted to Phys. Rev. Let
- …