2,350 research outputs found
Evidence for polarised boron in Co-B and Fe-B alloys
By exploiting the tunability of synchrotron radiation in measurements of spin-resolved photoemission it has proved possible to obtain information on the polarisation of the valence electrons of Co-B and Fe-B amorphous magnetic alloys, Both the spin-integrated and spin-resolved energy distribution curves show a marked dependence on photon energy indicating that the p states of boron hybridise with the d states of the transition metals giving rise to mixed states in the binding energy range 1 to 5 eV, The observed polarisation and spin-resolved densities of states imply that in the above restricted energy range there is a net negative polarisation of the boron states
Ultrathin epitaxial Fe films in vicinal GaAs(001): A study by spin-resolved photoelectron spectroscopy
Thin epitaxial Fe films have been grown on vicinal GaAs(001) substrates and their remanent magnetic properties and the degree of substrate atom diffusion investigated using synchrotron-based photoelectron spectroscopy. The vicinal Fe films, though exhibiting greater As diffusion than their singular homologues, displayed better film quality both from the structural and the magnetic points of view. The spin-resolved valence spectra of the vicinal films resemble those for crystalline bulk Fe at lower film thicknesses than for singular films
Results from EDGES High-Band: II. Constraints on Parameters of Early Galaxies
We use the sky-average spectrum measured by EDGES High-Band ( MHz) to
constrain parameters of early galaxies independent of the absorption feature at
~MHz reported by Bowman et al. (2018). These parameters represent
traditional models of cosmic dawn and the epoch of reionization produced with
the 21cmFAST simulation code (Mesinger & Furlanetto 2007, Mesinger et al.
2011). The parameters considered are: (1) the UV ionizing efficiency (),
(2) minimum halo virial temperature hosting efficient star-forming galaxies
(), (3) integrated soft-band X-ray luminosity (), and (4) minimum X-ray energy escaping the first
galaxies (), corresponding to a typical H column
density for attenuation through the interstellar medium. The High-Band spectrum
disfavors high values of and , which correspond
to signals with late absorption troughs and sharp reionization transitions. It
also disfavors intermediate values of , which
produce relatively deep and narrow troughs within the band. Specifically, we
rule out
( C.L.). We then combine the EDGES High-Band data with constraints on the
electron scattering optical depth from Planck and the hydrogen neutral fraction
from high- quasars. This produces a lower degeneracy between and
than that reported in Greig & Mesinger (2017a) using
the Planck and quasar constraints alone. Our main result in this combined
analysis is the estimate ~~ ( C.L.). We leave for future work the evaluation of
~cm models using simultaneously data from EDGES Low- and High-Band.Comment: Accepted in Ap
The restoration of Loch Leven, Scotland, UK
This paper reviews the progress made towards the restoration of Loch Leven, the largest lake in lowland Scotland, over the last 20 years. In particular, the importance of direct regulation and of setting water quality objectives and targets is examined. Various means of engaging with stakeholders and the general public are also considered. Success criteria and catchment management initiatives are described and briefly reviewed
IFN-γ-producing CD4+ T cells promote experimental cerebral malaria by modulating CD8+ T cell accumulation within the brain.
It is well established that IFN-γ is required for the development of experimental cerebral malaria (ECM) during Plasmodium berghei ANKA infection of C57BL/6 mice. However, the temporal and tissue-specific cellular sources of IFN-γ during P. berghei ANKA infection have not been investigated, and it is not known whether IFN-γ production by a single cell type in isolation can induce cerebral pathology. In this study, using IFN-γ reporter mice, we show that NK cells dominate the IFN-γ response during the early stages of infection in the brain, but not in the spleen, before being replaced by CD4(+) and CD8(+) T cells. Importantly, we demonstrate that IFN-γ-producing CD4(+) T cells, but not innate or CD8(+) T cells, can promote the development of ECM in normally resistant IFN-γ(-/-) mice infected with P. berghei ANKA. Adoptively transferred wild-type CD4(+) T cells accumulate within the spleen, lung, and brain of IFN-γ(-/-) mice and induce ECM through active IFN-γ secretion, which increases the accumulation of endogenous IFN-γ(-/-) CD8(+) T cells within the brain. Depletion of endogenous IFN-γ(-/-) CD8(+) T cells abrogates the ability of wild-type CD4(+) T cells to promote ECM. Finally, we show that IFN-γ production, specifically by CD4(+) T cells, is sufficient to induce expression of CXCL9 and CXCL10 within the brain, providing a mechanistic basis for the enhanced CD8(+) T cell accumulation. To our knowledge, these observations demonstrate, for the first time, the importance of and pathways by which IFN-γ-producing CD4(+) T cells promote the development of ECM during P. berghei ANKA infection
Planetary nebulae abundances and stellar evolution II
Context: In recent years mid- and far infrared spectra of planetary nebulae
have been analysed and lead to more accurate abundances. It may be expected
that these better abundances lead to a better understanding of the evolution of
these objects. Aims: The observed abundances in planetary nebulae are compared
to those predicted by the models of Karakas (2003) in order to predict the
progenitor masses of the various PNe used. The morphology of the PNe is
included in the comparison. Since the central stars play an important role in
the evolution, it is expected that this comparison will yield additional
information about them. Methods: First the nitrogen/oxygen ratio is discussed
with relation to the helium/hydrogen ratio. The progenitor mass for each PNe
can be found by a comparison with the models of Karakas. Then the present
luminosity of the central stars is determined in two ways: first by computing
the central star effective temperature and radius, and second by computing the
nebular luminosity from the hydrogen and helium lines. This luminosity is also
a function of the initial mass so that these two values of initial mass can be
compared. Results: Six of the seven bipolar nebulae can be identified as
descendants of high mass stars (4Msun - 6Msun) while the seventh is ambiguous.
Most of the elliptical PNe have central stars which descend from low initial
mass stars, although there are a few caveats which are discussed. There is no
observational evidence for a higher mass for central stars which have a high
carbon/oxygen ratio. The evidence provided by the abundance comparison with the
models of Karakas is consistent with the HR diagram to which it is compared. In
the course of this discussion it is shown how `optically thin' nebulae can be
separated from those which are 'optically thick'.Comment: 12 pages, 4 tables, 4 figures. Accepted for publication in A&
Serum Concentrations of Myostatin and Myostatin-Interacting Proteins do not differ between young and Scarcopenic elderly men
Peer reviewedPostprin
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