201 research outputs found
Optical Anisotropy of Porphyrin Nanocrystals Modified by the Electrochemical Dissolution
Reflectance anisotropy spectroscopy (RAS) coupled to an electrochemical cell represents a powerful tool to correlate changes in the surface optical anisotropy to changes in the electrochemical currents related to electrochemical reactions. The high sensitivity of RAS in the range of the absorption bands of organic systems, such as porphyrins, allows us to directly correlate the variations of the optical anisotropy signal to modifications in the solid-state aggregation of the porphyrin molecules. By combining in situ RAS to electrochemical techniques, we studied the case of vacuum-deposited porphyrin nanocrystals, which have been recently observed dissolving through electrochemical oxidation in diluted sulfuric acid. Specifically, we could identify the first stages of the morphological modifications of the nanocrystals, which we could attribute to the single-electron transfers involved in the oxidation reaction; in this sense, the simultaneous variation of the optical anisotropy with the electron transfer acts as a precursor of the dissolution process of porphyrin nanocrystals
SPOTS: The Search for Planets Orbiting Two Stars. I. Survey description and first observations
Direct imaging surveys for exoplanets commonly exclude binary stars from
their target lists, leaving a large part of the overall planet demography
unexplored. To address this gap in our understanding of planet formation and
evolution, we have launched the first direct imaging survey dedicated to
circumbinary planets: SPOTS, the Search for Planets Orbiting Two Stars. In this
paper, we discuss the theoretical context, scientific merit, and technical
feasibility of such observations, describe the target sample and observational
strategy of our survey, and report on the first results from our pilot survey
of 26 targets with the VLT NaCo facility. While we have not found any confirmed
substellar companions to date, a number of promising candidate companions
remain to be tested for common proper motion in upcoming follow-up
observations. We also report on the astrometry of the three resolved binaries
in our target sample. This pilot survey constitutes a successful proof of
concept for our survey strategy and paves the way for a second stage of
exploratory observations with VLT SPHERE.Comment: 12 pages, 4 figures, 3 tables. Accepted for publication in A&
The Anti-Inflammatory Agent Bindarit Attenuates the Impairment of Neural Development through Suppression of Microglial Activation in a Neonatal Hydrocephalus Mouse Model
Neonatal hydrocephalus presents with various degrees of neuroinflammation and long-term neurologic deficits in surgically treated patients, provoking a need for additional medical treatment. We previously reported elevated neuroinflammation and severe periventricular white matter damage in the progressive hydrocephalus (prh) mutant which contains a point mutation in the Ccdc39 gene, causing loss of cilia-mediated unidirectional CSF flow. In this study, we identified cortical neuropil maturation defects such as impaired excitatory synapse maturation and loss of homeostatic microglia, and swimming locomotor defects in early postnatal prh mutant mice. Strikingly, systemic application of the anti-inflammatory small molecule bindarit significantly supports healthy postnatal cerebral cortical development in the prh mutant. While bindarit only mildly reduced the ventricular volume, it significantly improved the edematous appearance and myelination of the corpus callosum. Moreover, the treatment attenuated thinning in cortical Layers II–IV, excitatory synapse formation, and interneuron morphogenesis, by supporting the ramified-shaped homeostatic microglia from excessive cell death. Also, the therapeutic effect led to the alleviation of a spastic locomotor phenotype of the mutant. We found that microglia, but not peripheral monocytes, contribute to amoeboid-shaped activated myeloid cells in prh mutants’ corpus callosum and the proinflammatory cytokines expression. Bindarit blocks nuclear factor (NF)-kB activation and its downstream proinflammatory cytokines, including monocyte chemoattractant protein-1, in the prh mutant. Collectively, we revealed that amelioration of neuroinflammation is crucial for white matter and neuronal maturation in neonatal hydrocephalus. Future studies of bindarit treatment combined with CSF diversion surgery may provide long-term benefits supporting neuronal development in neonatal hydrocephalus.
Do experiments suggest a hierarchy problem?
The hierarchy problem of the scalar sector of the standard model is
reformulated, emphasizing the role of experimental facts that may suggest the
existence of a new physics large mass scale, for instance indications of the
instability of the matter, or indications in favor of massive neutrinos. In the
see-saw model for the neutrino masses a hierarchy problem arises if the mass of
the right-handed neutrinos is larger than approximatively GeV: this
problem, and its possible solutions, are discussed.Comment: revtex, 4 pages, 1 figur
Support for UNRWA's survival
The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) provides life-saving humanitarian aid for 5·4 million Palestine refugees now entering their eighth decade of statelessness and conflict. About a third of Palestine refugees still live in 58 recognised camps. UNRWA operates 702 schools and 144 health centres, some of which are affected by the ongoing humanitarian disasters in Syria and the Gaza Strip. It has dramatically reduced the prevalence of infectious diseases, mortality, and illiteracy. Its social services include rebuilding infrastructure and homes that have been destroyed by conflict and providing cash assistance and micro-finance loans for Palestinians whose rights are curtailed and who are denied the right of return to their homeland
Spatially Resolved 3 micron Spectroscopy of Elias 1: Origin of Diamonds in Protoplanetary Disks
We present spatially resolved 3 um spectra of Elias 1 obtained with an
adaptive optics system. The central part of the disk is almost devoid of PAH
emission at 3.3 um; it shows up only at 30 AU and beyond. The PAH emission
extends up to 100 AU, at least to the outer boundary of our observation. The
diamond emission, in contrast, is more centrally concentrated, with the column
density peaked around 30 AU from the star. There are only three Herbig Ae/Be
stars known to date that show diamond emission at 3.53 um. Two of them have
low-mass companions likely responsible for the large X-ray flares observed
toward the Herbig Ae/Be stars. We speculate on the origin of diamonds in
circumstellar disks in terms of the graphitic material being transformed into
diamond under the irradiation of highly energetic particles.Comment: 7 pages, 4 figures, Accepted for publication in the Astrophysical
Journ
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