87 research outputs found
Resonant X-Ray Raman Spectra of Cu dd Excitations in Sr2CuO2Cl2
We present resonant x-ray Raman scattering results on Sr2CuO2Cl2, a model compound for high-Tc
superconductors. We demonstrate that the dd excitations can be observed and show that the polarization
dependence can be used to identify the dd excitations. We find the transition from the dx²-y² ground
state to the dxy excited state at 1.35 eV and to the degenerate dxz and dyz excited states at 1.7 eV. From
analysis of the polarization dependence we conclude that the d3z²-r² orbital energy is at 1.5 eV and not
in the midinfrared (0.5 eV) as recently suggested. We use recent theoretical arguments to show that
the d3z22r2 excitation is accompanied by a local spin flip resulting in a shift upwards of 0.2 eV due to
the exchange interaction with the neighboring spins
Observation of Strong Resonant Behavior in the Inverse Photoelectron Spectroscopy of Ce Oxide
X-ray emission spectroscopy and resonant inverse photoelectron spectroscopy (RIPES) have been used to investigate the photon emission associated with the Ce 3d5/2 and Ce 3d3/2 thresholds. Strong resonant behavior has been observed in the RIPES of a Ce oxide near the 5/2 and 3/2 edges
The Effect of Cone Opsin Mutations on Retinal Structure and the Integrity of the Photoreceptor Mosaic
Purpose.
To evaluate retinal structure and photoreceptor mosaic integrity in subjects with OPN1LW and OPN1MW mutations.
Methods.
Eleven subjects were recruited, eight of whom have been previously described. Cone and rod density was measured using images of the photoreceptor mosaic obtained from an adaptive optics scanning light ophthalmoscope (AOSLO). Total retinal thickness, inner retinal thickness, and outer nuclear layer plus Henle fiber layer (ONL+HFL) thickness were measured using cross-sectional spectral-domain optical coherence tomography (SD-OCT) images. Molecular genetic analyses were performed to characterize the OPN1LW/OPN1MW gene array.
Results.
While disruptions in retinal lamination and cone mosaic structure were observed in all subjects, genotype-specific differences were also observed. For example, subjects with “L/M interchange” mutations resulting from intermixing of ancestral OPN1LW and OPN1MW genes had significant residual cone structure in the parafovea (∼25% of normal), despite widespread retinal disruption that included a large foveal lesion and thinning of the parafoveal inner retina. These subjects also reported a later-onset, progressive loss of visual function. In contrast, subjects with the C203R missense mutation presented with congenital blue cone monochromacy, with retinal lamination defects being restricted to the ONL+HFL and the degree of residual cone structure (8% of normal) being consistent with that expected for the S-cone submosaic.
Conclusions.
The photoreceptor phenotype associated with OPN1LW and OPN1MW mutations is highly variable. These findings have implications for the potential restoration of visual function in subjects with opsin mutations. Our study highlights the importance of high-resolution phenotyping to characterize cellular structure in inherited retinal disease; such information will be critical for selecting patients most likely to respond to therapeutic intervention and for establishing a baseline for evaluating treatment efficacy
A High Docosahexaenoic Acid Diet Alters the Lung Inflammatory Response to Acute Dust Exposure
Agricultural workers are at risk for the development of acute and chronic lung diseases due to their exposure to organic agricultural dusts. A diet intervention using the omega-3 fatty acid docosahexaenoic acid (DHA) has been shown to be an effective therapeutic approach for alleviating a dust-induced inflammatory response. We thus hypothesized a high-DHA diet would alter the dust-induced inflammatory response through the increased production of specialized pro-resolving mediators (SPMs). Mice were pre-treated with a DHA-rich diet 4 weeks before being intranasally challenged with a single dose of an extract made from dust collected from a concentrated swine feeding operation (HDE). This omega-3-fatty-acid-rich diet led to reduced arachidonic acid levels in the blood, enhanced macrophage recruitment, and increased the production of the DHA-derived SPM Resolvin D1 (RvD1) in the lung following HDE exposure. An assessment of transcript-level changes in the immune response demonstrated significant differences in immune pathway activation and alterations of numerous macrophage-associated genes among HDE-challenged mice fed a high DHA diet. Our data indicate that consuming a DHA-rich diet leads to the enhanced production of SPMs during an acute inflammatory challenge to dust, supporting a role for dietary DHA supplementation as a potential therapeutic strategy for reducing dust-induced lung inflammation
Strengthening health systems for persons with traumatic spinal cord injury in South Africa and Sweden: a protocol for a longitudinal study of processes and outcomes
BACKGROUND: The provision of specialized care in a time-sensitive manner has shown
to be crucial for survival and recovery of functioning after a traumatic spinal cord injury
(TSCI). However, little is known about the provision of TSCI care in different international
contexts; information which is required for strengthening policy and practice.
AIMS: The overarching aim of this study will be to explore health care processes and
outcomes of TSCI care in South Africa and Sweden. Specific aims will be to: (1) describe
acute processes of TSCI care, (2) determine acute- and long-term outcomes of TSCI
care, and (3) identify predictors for survival, secondary complications, and functioning 12
months post-injury.
METHODS: A prospective (regional), population-based cohort study where adults
with an acute TSCI will be recruited over at least a 1-year period from the City
of Cape Town, South Africa, and Stockholm, Sweden. The anticipated sample size
inclusive of both international contexts will be 200 participants—based on a power
calculation for detecting differences in mortality. Information on the nature and timing
of processes of acute care (e.g., transfer logistics, spinal surgery, and specialized SCI
care) will be collected on acute care admission and discharge using a standardized
form. Survival status, secondary complications, neurological symptoms, functional
status, activity, and participation as well as health-related quality of life will be
collected at discharge from SCI acute care and at 12-months post-injury. Secondary
complications and functioning will be compared between South Africa and Sweden
using inferential statistics. To address mortality specifically, the indirect standardization
method for differences in mortality between contexts will be used whereby Stockholm
will serve as standard for specialize care. For the assessment of factors related to
mortality and other outcomes (e.g., neurological and secondary health conditions)
multivariate regression analyses will be used to determine independent risk factors.CONCLUSION: This study offers a unique investigation of the relationship between health
care processes and outcomes of TSCI care with the aim of strengthening management
guidelines for SCI in South Africa and Sweden
Orbital dynamics during an ultrafast insulator to metal transition
Phase transitions driven by ultrashort laser pulses have attracted interest
both for understanding the fundamental physics of phase transitions and for
potential new data storage or device applications. In many cases these
transitions involve transient states that are different from those seen in
equilibrium. To understand the microscopic properties of these states, it is
useful to develop elementally selective probing techniques that operate in the
time domain. Here we show fs-time-resolved measurements of V Ledge Resonant
Inelastic X-Ray Scattering (RIXS) from the insulating phase of the Mott-
Hubbard material V2O3 after ultrafast laser excitation. The probed orbital
excitations within the d-shell of the V ion show a sub-ps time response, which
evolve at later times to a state that appears electronically indistinguishable
from the high-temperature metallic state. Our results demonstrate the potential
for RIXS spectroscopy to study the ultrafast orbital dynamics in strongly
correlated materials.Comment: 12 pages, 4 figure
ACBD5 and VAPB mediate membrane associations between peroxisomes and the ER
This is the final version of the article. Available from the publisher via the DOI in this record.Peroxisomes (POs) and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism and form tight structural
associations, which were first observed in ultrastructural studies decades ago. PO–ER associations have been suggested
to impact on a diverse number of physiological processes, including lipid metabolism, phospholipid exchange, metabolite
transport, signaling, and PO biogenesis. Despite their fundamental importance to cell metabolism, the mechanisms
by which regions of the ER become tethered to POs are unknown, in particular in mammalian cells. Here, we identify
the PO membrane protein acyl-coenzyme A–binding domain protein 5 (ACBD5) as a binding partner for the resident
ER protein vesicle-associated membrane protein-associated protein B (VAPB). We show that ACBD5–VAPB interaction
regulates PO–ER associations. Moreover, we demonstrate that loss of PO–ER association perturbs PO membrane expansion
and increases PO movement. Our findings reveal the first molecular mechanism for establishing PO–ER associations
in mammalian cells and report a new function for ACBD5 in PO–ER tethering.This work was supported by grants from the Biotechnology and Biological
Sciences Research Council (BB/K006231/1 and BB/
N01541X/1 to M. Schrader). J. Metz and M. Schrader are supported
by a Wellcome Trust Institutional Strategic Support Award
(WT097835MF and WT105618MA) and L.F. Godinho by a fellowship
from Fundação para a Ciência e a Tecnologia, Portugal (SFRH/
BPD/90084/2012). M. Schrader and A.S. Azadi are supported by
Marie Curie Initial Training Network action PerFuMe (316723).
M. Islinger is supported by MEAMEDMA Anschubförderung, Medical
Faculty Mannheim, University of Heidelberg
XMM-Newton observations of the interacting galaxy pairs NGC7771/0 and NGC2342/1
We present XMM-Newton X-ray observations of the interacting galaxy pairs
NGC7771/7770 and NGC2342/2341. In NGC7771, for the first time we are able to
resolve the X-ray emission into a bright central source (L(X)~10^41 erg/s),
plus two (L(X)>10^40 erg/s) ultraluminous X-ray sources (ULXs) located either
end of the bar. The soft emission of the central source is well-modelled by a
two-temperature thermal plasma with kT=0.4/0.7 keV. The hard emission is
modelled with a flat absorbed power-law (Gamma~1.7, NH~10^22 cm^2), and this
together with a low-significance (1.7 sigma) ~300 eV equivalent width emission
line at ~6 keV are the first indications that NGC7771 may host a low-luminosity
AGN. For the bar ULXs, a power-law fit to X-1 is improved at the 2.5 sigma
level with the addition of a thermal plasma component (kT~0.3 keV), while X-2
is improved only at the 1.3 sigma level with the addition of a disc blackbody
component with T(in)~0.2 keV. Both sources are variable on short time-scales
implying that their emission is dominated by single accreting X-ray binaries
(XRBs). The three remaining galaxies, NGC7770, NGC2342 and NGC2341, have
observed X-ray luminosities of 0.2, 1.8 & 0.9x10^41 erg/s respectively (0.3-10
keV). Their integrated spectra are also well-modelled by multi-temperature
thermal plasma components with kT=0.2-0.7 keV, plus power-law continua with
slopes of Gamma=1.8-2.3 that are likely to represent the integrated emission of
populations of XRBs as observed in other nearby merger systems. A comparison
with other isolated, interacting and merging systems shows that all four
galaxies follow the established correlations for starburst galaxies between
X-ray, far-infrared and radio luminosities, demonstrating that their X-ray
outputs are dominated by their starburst components.Comment: 15 pages,7 figures. Accepted for publication in MNRA
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