643 research outputs found
Reentrant valence transition in EuO at high pressures: beyond the bond-valence model
The pressure-dependent relation between Eu valence and lattice structure in
model compound EuO is studied with synchrotron-based x-ray spectroscopic and
diffraction techniques. Contrary to expectation, a 7% volume collapse at
45 GPa is accompanied by a reentrant Eu valence transition into a
\emph{lower} valence state. In addition to highlighting the need for probing
both structure and electronic states directly when valence information is
sought in mixed-valent systems, the results also show that widely used
bond-valence methods fail to quantitatively describe the complex electronic
valence behavior of EuO under pressure.Comment: 5 pages, 4 figure
A general moment NRIXS approach to the determination of equilibrium Fe isotopic fractionation factors: application to goethite and jarosite
We measured the reduced partition function ratios for iron isotopes in
goethite FeO(OH), potassium-jarosite KFe3(SO4)2(OH)6, and hydronium-jarosite
(H3O)Fe3(SO4)2(OH)6, by Nuclear Resonant Inelastic X-Ray Scattering (NRIXS,
also known as Nuclear Resonance Vibrational Spectroscopy -NRVS- or Nuclear
Inelastic Scattering -NIS) at the Advanced Photon Source. These measurements
were made on synthetic minerals enriched in 57Fe. A new method (i.e., the
general moment approach) is presented to calculate {\beta}-factors from the
moments of the NRIXS spectrum S(E). The first term in the moment expansion
controls iron isotopic fractionation at high temperature and corresponds to the
mean force constant of the iron bonds, a quantity that is readily measured and
often reported in NRIXS studies.Comment: 38 pages, 2 tables, 8 figures. In press at Geochimica et Cosmochimica
Acta. Appendix C contains new derivations relating the moments of the iron
PDOS to the moments of the excitation probability function measured in
Nuclear Resonant Inelastic X-ray Scatterin
Magnetism dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
The phonon dispersion was measured at room temperature along (0,0,L) in the
tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized
first-principles calculations imposing various types of antiferromagnetic order
are in better agreement with the experimental results than nonmagnetic
calculations, although the measurements were made well above the magnetic
ordering temperature, T_N. Splitting observed between two A_{1g} phonon modes
at 22 and 26 meV is only observed in spin-polarized calculations.
Magneto-structural effects similar to those observed in the AFe_2As_2 materials
are confirmed present in LaFeAsO. The presence of Fe-spin is necessary to find
reasonable agreement of the calculations with the measured spectrum well above
T_N. On-site Fe and As force constants show significant softening compared to
nonmagnetic calculations, however an investigation of the real-space force
constants associates the magnetoelastic coupling with a complex renormalization
instead of softening of a specific pairwise force.Comment: 7 pages, 4 figure
Influence of Magnetism on Phonons in CaFe2As2 Via Inelastic X-ray Scattering
In the iron pnictides, the strong sensitivity of the iron magnetic moment to
the arsenic position suggests a significant relationship between phonons and
magnetism. We measured the phonon dispersion of several branches in the high
temperature tetragonal phase of CaFe2As2 using inelastic x-ray scattering on
single-crystal samples. These measurements were compared to ab initio
calculations of the phonons. Spin polarized calculations imposing the
antiferromagnetic order present in the low temperature orthorhombic phase
dramatically improve agreement between theory and experiment. This is discussed
in terms of the strong antiferromagnetic correlations that are known to persist
in the tetragonal phase.Comment: 4 pages, 3 figures; added additional information and references about
spin fluctuation
Dorsal Root Ganglia Macrophages Maintain Osteoarthritis Pain
Pain is the major debilitating symptom of osteoarthritis (OA), which is difficult to treat. In OA patients joint tissue damage only poorly associates with pain, indicating other mechanisms contribute to OA pain. Immune cells regulate the sensory system, but little is known about the involvement of immune cells in OA pain. Here, we report that macrophages accumulate in the dorsal root ganglia (DRG) distant from the site of injury in two rodent models of OA. DRG macrophages acquired an M1-like phenotype, and depletion of DRG macrophages resolved OA pain in male and female mice. Sensory neurons innervating the damaged knee joint shape DRG macrophages into an M1-like phenotype. Persisting OA pain, accumulation of DRG macrophages, and programming of DRG macrophages into an M1-like phenotype were independent of Nav1.8 nociceptors. Inhibition of M1-like macrophages in the DRG by intrathecal injection of an IL4-IL10 fusion protein or M2-like macrophages resolved persistent OA pain. In conclusion, these findings reveal a crucial role for macrophages in maintaining OA pain independent of the joint damage and suggest a new direction to treat OA pain.
SIGNIFICANCE STATEMENT: In OA patients pain poorly correlates with joint tissue changes indicating mechanisms other than only tissue damage that cause pain in OA. We identified that DRG containing the somata of sensory neurons innervating the damaged knee are infiltrated with macrophages that are shaped into an M1-like phenotype by sensory neurons. We show that these DRG macrophages actively maintain OA pain remotely and independent of joint damage. The phenotype of these macrophages is crucial for a pain-promoting role. Targeting the phenotype of DRG macrophages with either M2-like macrophages or a cytokine fusion protein that skews macrophages into an M2-like phenotype resolves OA pain. Our work reveals a mechanism that contributes to the maintenance of OA pain distant from the affected knee joint and suggests that dorsal root ganglia macrophages are a target to treat osteoarthritis chronic pain
Nitrosylation of Nitric-Oxide-Sensing Regulatory Proteins Containing [4Fe-4S] Clusters Gives Rise to Multiple Iron-Nitrosyl Complexes
The reaction of protein-bound iron–sulfur (Fe-S) clusters with nitric oxide (NO) plays key roles in NO-mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe-S clusters has been hampered by a lack of information about the nature of the iron-nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe-4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe2(NO)4(Cys)2]) and Roussin's Black Salt (RBS, [Fe4(NO)7S3]. In the latter case, the absence of 32S/34S shifts in the Fe−S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates
Sustainable peeling of Kapok Tree (Ceiba pentandra) bark by the chimpanzees (Pan troglodytes verus) of Comoé National Park, Ivory Coast
Primates often consume either bark or cambium (inner bark) as a fallback food to complete their diet during periods of food scarcity. Wild chimpanzees exhibit great behavioral diversity across Africa, as studies of new populations frequently reveal. Since 2014, we have been using a combination of camera traps and indirect signs to study the ecology and behavior of wild chimpanzees (Pan troglodytes verus) in Comoé National Park, Ivory Coast, to document and understand the behavioral adaptations that help them to survive in a savanna–forest mosaic landscape. We found that Comoé chimpanzees peel the bark of the buttresses of kapok tree (Ceiba pentandra) trees to eat the cambium underneath. Individuals of all sex/age classes across at least six neighboring communities peeled the bark, but only during the late rainy season and beginning of the dry season, when cambium may represent an important fallback food. Baboons (Papio anubis) also target the same trees but mainly eat the bark itself. Most of the bark-peeling wounds on Ceiba trees healed completely within 2 years, seemingly without any permanent damage. We recorded chimpanzees visiting trees in early stages of wound recovery but leaving them unpeeled. Only 6% of peeled trees (N = 53) were reexploited after a year, suggesting that chimpanzees waited for the rest of the trees to regrow the bark fully before peeling them again, thus using them sustainably. Many human groups of hunter-gatherers and herders exploited cambium sustainably in the past. The observation that similar sustainable bark-peeling behavior evolved in both chimpanzees and humans suggests that it has an important adaptive value in harsh environments when other food sources become seasonally scarce, by avoiding the depletion of the resource and keeping it available for periods of scarcity
Sobre a (im)prescritibilidade da pretensão de ressarcimento de danos causados ao erário por ato de improbidade administrativa
TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências JurÃdicas. Direito.O presente trabalho objetiva dirimir a dúvida existente acerca da sujeição da pretensão de ressarcimento de danos causados ao erário por ato de improbidade administrativa ao instituto da prescrição. Tal incerteza surge a partir da redação da ressalva contida no artigo 37, § 5º, da Constituição da República Federativa do Brasil, que possibilita variadas interpretações, algumas defendendo a imprescritibilidade de tal pretensão, outras advogando a tese da sujeição de tal pretensão a lapso prescricional. Com o fito de se concluir pelo entendimento mais condizente à ordem jurÃdico-normativa brasileira, divide-se o estudo em três capÃtulos principais. No primeiro, são delineados o conceito e a finalidade da prescrição, apresentando-se a garantia da segurança jurÃdica como sendo seu fundamento constitucional. Em seguida, são explanadas as noções de supremacia do interesse público e segurança jurÃdica, entendidas por boa parte dos estudiosos como os dois princÃpios a partir dos quais deve ser analisada a questão. Por fim, no terceiro e último capÃtulo, depois de serem descritas as principais interpretações que podem derivar da leitura do dispositivo, chega-se ao entendimento pela conformação da pretensão estudada ao manto prescricional. Esta acepção parece melhor se amoldar aos contornos pretendidos pelo ordenamento jurÃdico-constitucional contemporâneo para a construção de um Direito Administrativo efetivamente democrático, com a sobrevalorização dos direitos fundamentais, individuais e coletivos, e a realização da ideia de supremacia da Constituição. No plano legal e normativo, a compreensão pela prescritibilidade afigura-se coerente à própria construção histórica do comando constitucional, com a delimitação de dois regimes prescricionais distintos para as pretensões originadas com a prática de ato de improbidade. Da mesma forma, a identificação do ressarcimento como consequência, e não sanção, do ato Ãmprobo, bem como a evolução do tratamento dado à matéria pelo Supremo Tribunal Federal parecem caminhar no mesmo sentido interpretativo
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