86 research outputs found
Inhomogeneous magnetism in the doped kagome lattice of LaCuO2.66
The hole-doped kagome lattice of Cu2+ ions in LaCuO2.66 was investigated by
nuclear quadrupole resonance (NQR), electron spin resonance (ESR), electrical
resistivity, bulk magnetization and specific heat measurements. For
temperatures above ~180 K, the spin and charge properties show an activated
behavior suggestive of a narrow-gap semiconductor. At lower temperatures, the
results indicate an insulating ground state which may or may not be charge
ordered. While the frustrated spins in remaining patches of the original kagome
lattice might not be directly detected here, the observation of coexisting
non-magnetic sites, free spins and frozen moments reveals an intrinsically
inhomogeneous magnetism. Numerical simulations of a 1/3-diluted kagome lattice
rationalize this magnetic state in terms of a heterogeneous distribution of
cluster sizes and morphologies near the site-percolation threshold
Spin excitations in the antiferromagnet NaNiO2
In NaNiO2, Ni3+ ions form a quasi two dimensional triangular lattice of S =
1=2 spins. The magnetic order observed below 20K has been described as an A
type antiferromagnet with ferro- magnetic layers weakly coupled
antiferromagnetically. We studied the magnetic excitations with the electron
spin resonance for frequencies 1-20 cm-1, in magnetic fields up to 14 T. The
bulk of the results are interpreted in terms of a phenomenological model
involving bi-axial anisotropy for the spins: a strong easy-plane term, and a
weaker anisotropy within the plane. The direction of the easy plane is
constrained by the collective Jahn-Teller distortion occurring in this material
at 480 K
Mean-field Study of Charge, Spin, and Orbital Orderings in Triangular-lattice Compounds ANiO2 (A=Na, Li, Ag)
We present our theoretical results on the ground states in layered
triangular-lattice compounds ANiO2 (A=Na, Li, Ag). To describe the interplay
between charge, spin, orbital, and lattice degrees of freedom in these
materials, we study a doubly-degenerate Hubbard model with electron-phonon
couplings by the Hartree-Fock approximation combined with the adiabatic
approximation. In a weakly-correlated region, we find a metallic state
accompanied by \sqroot3x\sqroot3 charge ordering. On the other hand, we obtain
an insulating phase with spin-ferro and orbital-ferro ordering in a wide range
from intermediate to strong correlation. These phases share many
characteristics with the low-temperature states of AgNiO2 and NaNiO2,
respectively. The charge-ordered metallic phase is stabilized by a compromise
between Coulomb repulsions and effective attractive interactions originating
from the breathing-type electronphonon coupling as well as the Hund's-rule
coupling. The spin-orbital-ordered insulating phase is stabilized by the
cooperative effect of electron correlations and the Jahn-Teller coupling, while
the Hund's-rule coupling also plays a role in the competition with other
orbital-ordered phases. The results suggest a unified way of understanding a
variety of low-temperature phases in ANiO2. We also discuss a keen competition
among different spin-orbital-ordered phases in relation to a puzzling behavior
observed in LiNiO2
Long-term outcome of patients with combined post- and pre-capillary pulmonary hypertension
Aims: Pulmonary hypertension (PH) is a complex clinical condition, and left heart disease is the leading cause. Little is known about the epidemiology and prognosis of combined post- and pre-capillary PH (CpcPH).
Methods and results: This retrospective analysis of the Swiss PH Registry included incident patients with CpcPH registered from January 2001 to June 2019 at 13 Swiss hospitals. Patient baseline characteristics [age, sex, mean pulmonary artery pressure (mPAP), pulmonary artery wedge pressure (PAWP), pulmonary vascular resistance (PVR), and risk factors, including World Health Organization (WHO)-functional class (FC), 6 min walk distance (6MWD), and N-terminal pro-brain natriuretic peptide (NT-proBNP), treatment, days of follow-up, and events (death or loss to follow-up) at last visit] were analysed by Kaplan-Meier and Cox regression analyses. Two hundred and thirty-one patients (59.3% women, age 65 ± 12 years, mPAP 48 ± 11 mmHg, PAWP 21 ± 5 mmHg, PVR 7.2 ± 4.8 WU) were included. Survival analyses showed a significantly longer survival for women [hazard ratio (HR) 0.58 (0.38-0.89); P = 0.01] and a higher mortality risk for mPAP > 46 mmHg [HR 1.58 (1.03-2.43); P = 0.04] but no association with age or PVR. Patients stratified to high risk according to four-strata risk assessment had an increased mortality risk compared with patients stratified to low-intermediate risk [HR 2.44 (1.23-4.84); P = 0.01]. A total of 46.8% of CpcPH patients received PH-targeted pharmacotherapy; however, PH-targeted medication was not associated with longer survival.
Conclusion: Among patients with CpcPH, women and patients with an mPAP ≤46 mmHg survived longer. Furthermore, risk stratification by using non-invasively assessed risk factors, such as WHO-FC, 6MWD, and NT-proBNP, as proposed for pulmonary arterial hypertension, stratified survival in CpcPH, and might be helpful in the management of these patients
Long-term outcome of patients with combined post- and pre-capillary pulmonary hypertension.
AIMS
Pulmonary hypertension (PH) is a complex clinical condition, and left heart disease is the leading cause. Little is known about the epidemiology and prognosis of combined post- and pre-capillary PH (CpcPH).
METHODS AND RESULTS
This retrospective analysis of the Swiss PH Registry included incident patients with CpcPH registered from January 2001 to June 2019 at 13 Swiss hospitals. Patient baseline characteristics [age, sex, mean pulmonary artery pressure (mPAP), pulmonary artery wedge pressure (PAWP), pulmonary vascular resistance (PVR), and risk factors, including World Health Organization (WHO)-functional class (FC), 6 min walk distance (6MWD), and N-terminal pro-brain natriuretic peptide (NT-proBNP), treatment, days of follow-up, and events (death or loss to follow-up) at last visit] were analysed by Kaplan-Meier and Cox regression analyses. Two hundred and thirty-one patients (59.3% women, age 65 ± 12 years, mPAP 48 ± 11 mmHg, PAWP 21 ± 5 mmHg, PVR 7.2 ± 4.8 WU) were included. Survival analyses showed a significantly longer survival for women [hazard ratio (HR) 0.58 (0.38-0.89); P = 0.01] and a higher mortality risk for mPAP > 46 mmHg [HR 1.58 (1.03-2.43); P = 0.04] but no association with age or PVR. Patients stratified to high risk according to four-strata risk assessment had an increased mortality risk compared with patients stratified to low-intermediate risk [HR 2.44 (1.23-4.84); P = 0.01]. A total of 46.8% of CpcPH patients received PH-targeted pharmacotherapy; however, PH-targeted medication was not associated with longer survival.
CONCLUSION
Among patients with CpcPH, women and patients with an mPAP ≤46 mmHg survived longer. Furthermore, risk stratification by using non-invasively assessed risk factors, such as WHO-FC, 6MWD, and NT-proBNP, as proposed for pulmonary arterial hypertension, stratified survival in CpcPH, and might be helpful in the management of these patients
Seasonal and Regional Dynamics of M. ulcerans Transmission in Environmental Context: Deciphering the Role of Water Bugs as Hosts and Vectors
Buruli ulcer, caused by Mycobacterium ulcerans, is a devastating skin disease. Most cases of Buruli ulcer occur in poor rural communities. As a result, treatment is frequently sought too late and about 25% of those infected—particularly children—become permanently disabled. Outbreaks of Buruli ulcer have always been associated with swampy areas. However, the route(s) of bacillus transmission is (are) still unclear. This Mycobacterium species resides in water where it colonizes many ecological niches such as aquatic plants, herbivorous animals and predatory/carnivorous insects. For several years the role of water bugs as hosts and vectors of M. ulcerans was suspected and was demonstrated under laboratory conditions. The aim of this work was to further assess the role of water bugs as hosts and vectors of M. ulcerans in environmental context. This work identifies several water bug families as hosts of M. ulcerans in Buruli ulcer endemic area. The detection of bacilli in saliva of human biting insects provides further evidence for their role in M. ulcerans transmission. Interestingly, three of these insects are good flyers, and as such could participate in M. ulcerans dissemination
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