83 research outputs found
An extended Falicov-Kimball model on a triangular lattice
The combined effect of frustration and correlation in electrons is a matter
of considerable interest of late. In this context a Falicov-Kimball model on a
triangular lattice with two localized states, relevant for certain correlated
systems, is considered. Making use of the local symmetries of the model, our
numerical study reveals a number of orbital ordered ground states, tuned by the
small changes in parameters while quantum fluctuations between the localized
and extended states produce homogeneous mixed valence. The inversion symmetry
of the Hamiltonian is broken by most of these ordered states leading to
orbitally driven ferroelectricity. We demonstrate that there is no spontaneous
symmetry breaking when the ground state is inhomogeneous. The study could be
relevant for frustrated systems like , (in its low temperature
C2/m phase) where two Mott localized states couple to a conduction band.Comment: 6 pages, 8 figure
New magnetic phase in metallic V_{2-y}O_3 close to the metal insulator transition
We have observed two spin density wave (SDW) phases in hole doped metallic
V_{2-y}O_3, one evolves from the other as a function of doping, pressure or
temperature. They differ in their response to an external magnetic field, which
can also induce a transition between them. The phase boundary between these two
states in the temperature-, doping-, and pressure-dependent phase diagram has
been determined by magnetization and magnetotransport measurements. One phase
exists at high doping level and has already been described in the literature.
The second phase is found in a small parameter range close to the boundary to
the antiferromagnetic insulating phase (AFI). The quantum phase transitions
between these states as a function of pressure and doping and the respective
metamagnetic behavior observed in these phases are discussed in the light of
structurally induced changes of the band structure.Comment: REVTeX, 8 pages, 12 EPS figures, submitted to PR
Theory for Phase Transitions in Insulating Vanadium Oxide
We show that the recently proposed S=2 bond model with orbital degrees of
freedom for insulating VO not only explains the anomalous magnetic
ordering, but also other mysteries of the magnetic phase transition. The model
contains an additional orbital degree of freedom that exhibits a zero
temperature quantum phase transtion in the Ising universality class.Comment: 5 pages, 2 figure
Differential diagnosis of amiodarone-induced thyrotoxicosis in a patient with atrial fibrillation and agranulocytosis on the background of thyrostatic therapy. Case report
Atrial fibrillation is the most common heart rhythm disorder in patients with chronic heart failure. One of the most effective antiarrhythmic drugs for the treatment and prevention of a wide range of supraventricular and ventricular tachyarrhythmia is amiodarone. In the group of patients with paroxysmal atrial fibrillation and low left ventricular ejection fraction, it is the drug of choice when conducting a „rhythm control“ strategy. Patients receiving amiodarone often develop an adverse event – amiodarone-induced thyrotoxicosis, which exacerbates the course of cardiovascular pathology. In this article, we consider a clinical case of amiodarone-induced thyrotoxicosis in a 30-year-old patient with dilated cardiomyopathy and agranulocytosis that developed against the background of thyrostatic therapy
Orbitally Degenerate Spin-1 Model for Insulating V2O3
Motivated by recent neutron, X-ray absorption and resonant scattering
experiments, we revisit the electronic structure of V2O3. We propose a model in
which S=1 V3+ ions are coupled in the vertical V-V pairs forming two-fold
orbitally degenerate configurations with S=2. Ferro-orbital ordering of the V-V
pairs gives a description which is consistent with all experiments in the
antiferromagnetic insulating phase.Comment: 4 pages, including three figure
Lipoprotein(a) concentration and the blood content of INFγ-producing T-helpers 17 (Th17/1) in males with premature coronary artery disease
Aim. To analyze the relationship of blood lipid profile parameters, including the level of lipoprotein(a) (Lp(a)), and the content of circulating CD4+ T-lymphocytes with premature coronary artery disease (CAD).Material and methods. This retrospective cross-sectional study included 76 men aged 40 to 79 years. Patients were divided into following groups: main group — patients with CAD (58 [54;64] years, n=56) onset before the age of 55; control group — patients (62 [57;66] years, n=20) without CAD and obstructive CAD and peripheral arterial disease. Statins were taken by 51 (91%) and 9 (45%) patients in the main and control groups, respectively. In serum and plasma samples, lipid spectrum parameters and Lp(a) concentration were determined. Cellular phenotyping was performed by direct immunofluorescence in a culture of mononuclear leukocytes isolated from blood. To determine cytokines, cells were in vitro activated with inhibitor of intracellular transport of secretory proteins. Cell fluorescence was determined using flow cytometry.Results. Patients of both groups were comparable in age, body mass index, prevalence of hypertension and diabetes. Blood Lp(a) concentrations were higher in the CAD group than in the control group (49 [10;102] mg/dL vs 12 [4,3;32] mg/ dL, p<0,05). The content of INFγ-producing T-helpers 17 (Th17/1) was also higher in the CAD group (19 [15;24] vs 13 [11;22], % of Th17, p=0,05). Logistic regression revealed that elevated Lp(a) levels (≥30 mg/dL) and relative amounts of Th17/1 (>14% of Th17) independently of each other, atherogenic lipoprotein cholesterol levels, classical risk factors, and statin use were associated with premature CAD in the general group of patients with odds ratio (OR) of 4,6 (95% confidence interval (CI), 1,1-20,2) and 10,9 (2,1-56,7), p<0,05, respectively. The combination of Lp(a) >30 mg/dl and Th17/1 over 14% significantly increased the risk of premature CAD (OR, 28,0, 95% CI, 4,31-181,75, p=0,0005).Conclusion. We have shown for the first time that an increased Lp(a) concentration with an increased Th17/1 content is associated with the premature CAD in men
Electronic Structure and Phase Transition in V2O3: Importance of 3d Spin-Orbit Interaction and Lattice Distortion
The 3d electronic structure and phase transition in pure and Cr doped V2O3
are theoretically investigated in relation to the 3d spin-orbit interaction and
lattice distortion. A model consisting of the nearest-neighbor V ion pair with
full degeneracy of the 3d orbitals is studied within the many-body point of
view. It is shown that each V ion with S=1 spin state has a large orbital
magnetic moment and no orbital ordering occurs in the
antiferromagnetic insulating (AFI) phase. The anomalous resonant Bragg
reflection found in the AFI phase is attributed to the magnetic ordering. In
the AFI and paramagnetic insulating (PI) phases, Jahn-Teller like lattice
instability leads to tilting of the V ion pairs from the corundum c-axis and
this causes large difference in the orbital occupation between the paramagnetic
metal and the insulating phases, which is consistent with linear dichroic V 2p
XAS measurements.
To understand the AFI to PI transition, a model spin Hamiltonian is also
proposed. The transition is found to be simultaneous order-disorder transition
of the magnetic moments and tilting directions of the V ion pairs. Softening of
elastic constant C44 and abrupt change in short range spin correlations
observed at the transition are also explained.Comment: 18 pages, 16 figure
Electronic structure of Co_xTiSe_2 and Cr_xTiSe_2
The results of investigations of intercalated compounds Cr_xTiSe_2 and
Co_xTiSe_2 by X-ray photoelectron spectroscopy (XPS) and X-ray emission
spectroscopy (XES) are presented. The data obtained are compared with
theoretical results of spin-polarized band structure calculations. A good
agreement between theoretical and experimental data for the electronic
structure of the investigated materials has been observed. The interplay
between the M3d--Ti3d hybridization (M=Cr, Co) and the magnetic moment at the M
site is discussed. A 0.9 eV large splitting of the core Cr2p{3/2} level was
observed, which reveals a strong exchange magnetic interaction of 3d-2p
electrons of Cr. In the case of a strong localization of the Cr3d electrons
(for x<0.25), the broadening of the CrL spectra into the region of the states
above the nominal Fermi level was observed and attributed to X-ray re-emission.
The measured kinetic properties are in good accordance with spectral
investigations and band calculation results.Comment: 14 pages, 11 figures, submitted to Phys.Rev.
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some
references added, minor typos correcte
- …