13 research outputs found
Singlet magnetism in intermetallic UGa unveiled by inelastic x-ray scattering
Using high resolution tender-x-ray resonant inelastic scattering and
hard-x-ray non-resonant inelastic scattering beyond the dipole limit we were
able to detect electronic excitations in intermetallic UGa that are highly
atomic in nature. Analysis of the spectral lineshape reveals that the local
configuration characterizes the correlated nature of this ferromagnet.
The orientation and directional dependence of the spectra indicate that the
ground state is made of the singlet and/or doublet
symmetry. With the ordered moment in the plane, we infer that the
magnetism originates from the higher lying doublet being mixed with
the singlet due to inter-site exchange, qualifying UGa to be a
true quantum magnet. The ability to observe atomic excitations is crucial to
resolve the on-going debate about the degree of localization versus itineracy
in U intermetallics.Comment: 9 pages, 7 figure
Induced Attenuation of Scleral TGF-β Signaling in Mutant Mice Increases Susceptibility to IOP-Induced Optic Nerve Damage
Purpose: Axonal optic nerve (ON) damage in glaucoma is characteristically associated with increased amounts of active transforming growth factor-beta 2 (TGF-β2) in the ON head. Here we investigated the functional role of scleral TGF-β signaling in glaucoma.
Methods: A deficiency of Tgfbr2, which encodes for TGF-β receptor type II (TGF-βRII), the essential receptor for canonical TGF-β signaling, was induced in fibroblasts (including those of the sclera) of mutant mice. To this end, 5-week-old mice were treated with tamoxifen eye drops. Experimental glaucoma was induced in 8-week-old mice using a magnetic microbead (MB) model. After 6 weeks of high intraocular pressure (IOP), the ON axons and their somata in the retina were labeled by paraphenylenediamine (PPD) and RNA-binding protein with multiple splicing (RBPMS) immunohistochemistry, respectively, and quantified.
Results: Tamoxifen treatment resulted in a significant decrease of TGF-βRII and its mRNA in the sclera. After 6 weeks of high IOP, reduced numbers of PPD-stained ON axons were seen in MB-injected eyes in comparison with not-injected contralateral eyes. Moreover, MB injection also led to a decrease of retinal ganglion cell (RGC) somata as seen in RBPMS-stained retinal wholemounts. Axon loss and RGC loss were significantly higher in mice with a fibroblast specific deficiency of TGF-βRII in comparison with control animals.
Conclusions: We conclude that the ablation of scleral TGF-β signaling increases the susceptibility to IOP-induced ON damage. Scleral TGF-β signaling in mutant mice appears to be beneficial for ON axon survival in experimentally induced glaucoma
Doping-dependent charge order correlations in electron-doped cuprates
Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2−xCexCuO4 and Nd2−xCexCuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2−xCexCuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates
Nature of the current-induced insulator-to-metal transition in CaRuO as revealed by transport-ARPES
The Mott insulator CaRuO exhibits a rare insulator-to-metal
transition (IMT) induced by DC current. While structural changes associated
with this transition have been tracked by neutron diffraction, Raman
scattering, and x-ray spectroscopy, work on elucidating the response of the
electronic degrees of freedom is still in progress. Here we unveil the
current-induced modifications of the electronic states of CaRuO by
employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with
four-probe transport. Two main effects emerge: a clear reduction of the Mott
gap and a modification in the dispersion of the Ru-bands. The changes in
dispersion occur exclusively along the high-symmetry direction, parallel
to the -axis where the greatest in-plane lattice change occurs. These
experimental observations are reflected in dynamical mean-field theory (DMFT)
calculations simulated exclusively from the current-induced lattice constants,
indicating a current driven structural transition as the primary mechanism of
the IMT. Furthermore, we demonstrate this phase is distinct from the
high-temperature zero-current metallic phase. Our results provide insight into
the elusive nature of the current-induced IMT of CaRuO and advance the
challenging, yet powerful, technique of transport-ARPES.Comment: 8 pages, 4 figure
Fano interference of the Higgs mode in cuprate high-Tc superconductors
Despite decades of search for the pairing boson in cuprate high-Tc
superconductors, its identity still remains debated to date. For this reason,
spectroscopic signatures of electron-boson interactions in cuprates have always
been a center of attention. For example, the kinks in the quasiparticle
dispersion observed by angle-resolved photoemission spectroscopy (ARPES)
studies have motivated a decade-long investigation of electron-phonon as well
as electron-paramagnon interactions in cuprates. On the other hand, the overlap
between the charge-order correlations and the pseudogap in the cuprate phase
diagram has also generated discussions about the potential link between them.
In the present study, we provide a fresh perspective on these intertwined
interactions using the novel approach of Higgs spectroscopy, i.e. an
investigation of the amplitude oscillations of the superconducting order
parameter driven by a terahertz radiation. Uniquely for cuprates, we observe a
Fano interference of its dynamically driven Higgs mode with another collective
mode, which we reveal to be charge density wave fluctuations from an extensive
doping- and magnetic field-dependent study. This finding is further
corroborated by a mean field model in which we describe the microscopic
mechanism underlying the interaction between the two orders. Our work
demonstrates Higgs spectroscopy as a novel and powerful technique for
investigating intertwined orders and microscopic processes in unconventional
superconductors
Mitochondrial oxidative stress and nitrate tolerance – comparison of nitroglycerin and pentaerithrityl tetranitrate in Mn-SOD(+/- )mice
BACKGROUND: Chronic therapy with nitroglycerin (GTN) results in a rapid development of nitrate tolerance which is associated with an increased production of reactive oxygen species (ROS). According to recent studies, mitochondrial ROS formation and oxidative inactivation of the organic nitrate bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) play an important role for the development of nitrate and cross-tolerance. METHODS: Tolerance was induced by infusion of wild type (WT) and heterozygous manganese superoxide dismutase mice (Mn-SOD(+/-)) with ethanolic solution of GTN (12.5 μg/min/kg for 4 d). For comparison, the tolerance-free pentaerithrityl tetranitrate (PETN, 17.5 μg/min/kg for 4 d) was infused in DMSO. Vascular reactivity was measured by isometric tension studies of isolated aortic rings. ROS formation and aldehyde dehydrogenase (ALDH-2) activity was measured in isolated heart mitochondria. RESULTS: Chronic GTN infusion lead to impaired vascular responses to GTN and acetylcholine (ACh), increased the ROS formation in mitochondria and decreased ALDH-2 activity in Mn-SOD(+/- )mice. In contrast, PETN infusion did not increase mitochondrial ROS formation, did not decrease ALDH-2 activity and accordingly did not lead to tolerance and cross-tolerance in Mn-SOD(+/- )mice. PETN but not GTN increased heme oxygenase-1 mRNA in EA.hy 926 cells and bilirubin efficiently scavenged GTN-derived ROS. CONCLUSION: Chronic GTN infusion stimulates mitochondrial ROS production which is an important mechanism leading to tolerance and cross-tolerance. The tetranitrate PETN is devoid of mitochondrial oxidative stress induction and according to the present animal study as well as numerous previous clinical studies can be used without limitations due to tolerance and cross-tolerance
Estrategias pedagógicas para contribuir al desarrollo de cultura ambiental en los estudiantes de grado sexto de la institución educativa santa cruz de lorica
La investigación se realizó con el propósito de contribuir al desarrollo de cultura ambiental en los niños de la Institución Educativa Santa Cruz de Lorica, debido al comportamiento de éstos en el ámbito escolar, social y ambiental, una de las formas para determinar la situación presentada fueron observaciones directas al entorno del plantel, del mismo modo se realizaron encuestas y posteriormente se elaboró un diagnóstico, esto se efectuó tomando una muestra de la población total como método de análisis. La investigación fue cualitativa y en tipo de diseño de investigación utilizado fue investigación-acción, lo que permitió encontrar vías apropiadas para seleccionar y aplicar las estrategias pedagógicas necesarias que lograron hacerle frente a la problemática encontrada, las cuales luego de su aplicación arrojaron resultados positivos como un mejor aprendizaje por parte de los estudiantes haciendo mejor relación de cómo llevar lo teórico a la práctica y así un mayor compromiso con respecto al cuidado del ambiente, demostrando que son un medio de enseñanza para despertar en los estudiantes el interés por cuidar el entorno escolar y el medio ambiente, de esta forma se aclararon conceptos, los cuales fueron incluidos por los estudiantes en sus esquemas de aprendizaje; logrando concluir de esta forma que las estrategias pedagógicas utilizadas de forma conjunta y con un mismo propósito causaron un impacto favorable en los estudiantes, estimulando en ellos la necesidad de cambiar sus actitudes en cuanto al cuidado del medio ambiente de su escuela o del lugar donde ellos se encuentren.Pregrad
Singlet magnetism in intermetallic unveiled by inelastic x-ray scattering
Using high resolution tender x-ray resonant inelastic scattering and hard x-ray nonresonant inelastic scattering beyond the dipole limit we were able to detect electronic excitations in intermetallic UGa that are highly atomic in nature. Analysis of the spectral lineshape reveals that the local 5f configuration characterizes the correlated nature of this ferromagnet. The orientation and directional dependence of the spectra indicate that the ground state is made of the singlet and/or doublet symmetry. With the ordered moment in the ab plane, we infer that the magnetism originates from the higher lying doublet being mixed with the singlet due to intersite exchange, qualifying UGa to be a true quantum magnet. The ability to observe atomic excitations is crucial to resolve the ongoing debate about the degree of localization versus itineracy in U intermetallics
Research data: Fano interference between collective modes in cuprate high-Tc superconductors
Research data and metadata that was used in the corresponding publication "Fano interference between collective modes
in cuprate high-Tc superconductors" ( https://doi.org/10.1038/s41467-023-36787-4 )
Early probiotic supplementation and the risk of celiac disease in children at genetic risk
Abstract
Probiotics are linked to positive regulatory effects on the immune system. The aim of the study was to examine the association between the exposure of probiotics via dietary supplements or via infant formula by the age of 1 year and the development of celiac disease autoimmunity (CDA) and celiac disease among a cohort of 6520 genetically susceptible children. Use of probiotics during the first year of life was reported by 1460 children. Time-to-event analysis was used to examine the associations. Overall exposure of probiotics during the first year of life was not associated with either CDA (n = 1212) (HR 1.15; 95%CI 0.99, 1.35; p = 0.07) or celiac disease (n = 455) (HR 1.11; 95%CI 0.86, 1.43; p = 0.43) when adjusting for known risk factors. Intake of probiotic dietary supplements, however, was associated with a slightly increased risk of CDA (HR 1.18; 95%CI 1.00, 1.40; p = 0.043) compared to children who did not get probiotics. It was concluded that the overall exposure of probiotics during the first year of life was not associated with CDA or celiac disease in children at genetic risk