1,153 research outputs found
Dzyaloshinsky-Moriya interaction in vesignieite: A route to freezing in a quantum kagome antiferromagnet
We report an electron spin resonance investigation of the geometrically
frustrated spin-1/2 kagome antiferromagnet vesignieite,
BaCuVO(OH). Analysis of the line widths and line shifts
indicates the dominance of in-plane Dzyaloshinsky-Moriya anisotropy that is
proposed to suppress strongly quantum spin fluctuations and thus to promote
long-range ordering rather than a spin-liquid state. We also evidence an
enhanced spin-phonon contribution that might originate from a lattice
instability and discuss the origin of a low-temperature mismatch between
intrinsic and bulk susceptibility in terms of local inhomogeneity
Haydeeite: a spin-1/2 kagome ferromagnet
The mineral haydeeite, alpha-MgCu3(OD)6Cl2, is a S=1/2 kagome ferromagnet
that displays long-range magnetic order below TC=4.2 K with a strongly reduced
moment. Our inelastic neutron scattering data show clear spin-wave excitations
that are well described by a Heisenberg Hamiltonian with ferromagnetic
nearest-neighbor exchange J1=-38 K and antiferromagnetic exchange Jd=+11 K
across the hexagons of the kagome lattice. These values place haydeeite very
close to the quantum phase transition between ferromagnetic order and
non-coplanar twelve-sublattice cuboc2 antiferromagnetic order. Diffuse dynamic
short-range ferromagnetic correlations observed above TC persist well into the
ferromagnetically ordered phase with a behavior distinct from critical
scattering
Hydrologic reinforcement induced by contrasting woody species during summer and winter
Aims: Vegetation can improve slope stability by transpiration-induced suction (hydrologic reinforcement). However, hydrologic reinforcement varies with seasons, especially under temperate climates. This study aims to quantify and compare the hydrologic reinforcement provided by contrasting species during winter and summer.Methods: One deciduous (Corylus avellana) and two evergreens (Ilex aquifolium and Ulex europaeus) were planted in 1-m soil columns. Soil columns were irrigated, left for evapotranspiration and then subjected to extreme wetting events during both summer and winter. Soil water content, matric suction and strength were measured down the soil profile. Plant water status and growth (above- and below-ground) were also recorded.Results: The tested species showed differing abilities to remove water, induce suction and hence influence soil strength. During summer, only Ulex europaeus provided a soil strength gain (up to six-fold the value at saturation) along the entire depth-profile inducing high suction (e.g. 70 kPa), largely maintained after wetting events in deeper soil (0.7 m). During winter, the evergreen species could remove water but at slower rates compared to summer.Conclusions: Evergreens could slowly induce suction and hence potentially stabilise slopes during winter. However, there were large differences between the two evergreens because of different growth rate and resource use
Vesignieite: a kagome antiferromagnet with dominant third-neighbor exchange
The spin- kagome antiferromagnet is an archetypal frustrated
system predicted to host a variety of exotic magnetic states. We show using
neutron scattering measurements that deuterated vesignieite
BaCuVO(OD), a fully stoichiometric kagome
magnet with 1% lattice distortion, orders magnetically at
K into a multi-k coplanar variant of the predicted triple-k
octahedral structure. We find this structure is stabilized by a dominant
antiferromagnetic 3-neighbor exchange with minor
1- or 2--neighbour exchange. The spin-wave
spectrum is well described by a -only model including a tiny symmetric
exchange anisotropy
Particle Fluxes and Transport Proceses Along the Continental Margins and in Deep Sea Environments.
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Vibroacoustic optimization of anti-tetrachiral and auxetic hexagonal sandwich panels with gradient geometry
Drying of fibrous roots strengthens the negative power relation between biomechanical properties and diameter
Genetic Features of Metachronous Esophageal Cancer Developed in Hodgkin's Lymphoma or Breast Cancer Long-Term Survivors: An Exploratory Study.
Background
Development of novel therapeutic drugs and regimens for cancer treatment has led to improvements in patient long-term survival. This success has, however, been accompanied by the increased occurrence of second primary cancers. Indeed, patients who received regional radiotherapy for Hodgkin's Lymphoma (HL) or breast cancer may develop, many years later, a solid metachronous tumor in the irradiated field. Despite extensive epidemiological studies, little information is available on the genetic changes involved in the pathogenesis of these solid therapy-related neoplasms.
Methods
Using microsatellite markers located in 7 chromosomal regions frequently deleted in sporadic esophageal cancer, we investigated loss of heterozygosity (LOH) and microsatellite instability (MSI) in 46 paired (normal and tumor) samples. Twenty samples were of esophageal carcinoma developed in HL or breast cancer long-term survivors: 14 squamous cell carcinomas (ESCC) and 6 adenocarcinomas (EADC), while 26 samples, used as control, were of sporadic esophageal cancer (15 ESCC and 11 EADC).
Results
We found that, though the overall LOH frequency at the studied chromosomal regions was similar among metachronous and sporadic tumors, the latter exhibited a statistically different higher LOH frequency at 17q21.31 (p = 0.018). By stratifying for tumor histotype we observed that LOH at 3p24.1, 5q11.2 and 9p21.3 were more frequent in ESCC than in EADC suggesting a different role of the genetic determinants located nearby these regions in the development of the two esophageal cancer histotypes.
Conclusions
Altogether, our results strengthen the genetic diversity among ESCC and EADC whether they occurred spontaneously or after therapeutic treatments. The presence of histotype-specific alterations in esophageal carcinoma arisen in HL or breast cancer long-term survivors suggests that their transformation process, though the putative different etiological origin, may retrace sporadic ESCC and EADC carcinogenesis
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