17 research outputs found
A Music index of periodicals for the first six months of 1948 /
Thesis (M.M.)--Boston Universit
Measuring and Modelling the Redshift Evolution of Clustering: the Hubble Deep Field North
(abridged) The evolution of galaxy clustering from z=0 to z=4.5 is analyzed
using the angular correlation function and the photometric redshift
distribution of galaxies brighter than I_{AB}\le 28.5 in the HDF North. The
reliability of the photometric redshift estimates is discussed on the basis of
the available spectroscopic redshifts, comparing different codes and
investigating the effects of photometric errors. The redshift bins in which the
clustering properties are measured are then optimized to take into account the
uncertainties of the photometric redshifts. The results show that the comoving
correlation length has a small decrease in the range 0<z<1 followed by an
increase at higher z. We compare these results with the theoretical predictions
of a variety of cosmological models belonging to the general class of CDM. The
comparison with the expected mass clustering evolution indicates that the
observed high-redshift galaxies are biased tracers of the dark matter with an
effective bias b strongly increasing with redshift. Assuming an Einstein-de
Sitter universe, we obtain b\simeq 2 at z=2 and b\simeq 5 at z=4. A comparison
of the clustering amplitudes that we measured at z=3 with those reported for
LBG suggests that the clustering depends on the abundance of the objects: more
abundant objects are less clustered, as expected in the paradigm of
hierarchical galaxy formation. The strong clustering and high bias measured at
z=3 are consistent with the expected density of massive haloes predicted for
the various cosmologies here considered. At z=4, the strong clustering observed
in the HDF requires a significant fraction of massive haloes to be already
formed by that epoch. This feature could be a discriminant test for the
cosmological parameters if confirmed by future observations.Comment: 23 pages, Latex using MN style, figures enclosed. Version accepted
for publication in MNRA
Dwarf Elliptical Galaxies
Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically
fainter than , are the most numerous type of galaxy in the nearby
universe. Tremendous advances have been made over the past several years in
delineating the properties of both Local Group satellite dE's and the large dE
populations of nearby clusters. We review some of these advances, with
particular attention to how well currently available data can constrain 1)
models for the formation of dE's, 2) the physical and evolutionary connections
between different types of galaxies (nucleated and nonnucleated dE's, compact
E's, irregulars, and blue compact dwarfs) that overlap in the same portion of
the mass-spectrum of galaxies, 3) the contribution of dE's to the galaxy
luminosity functions in clusters and the field, 4) the star-forming histories
of dE's and their possible contribution to faint galaxy counts, and 5) the
clustering properties of dE's. In addressing these issues, we highlight the
extent to which selection effects temper these constraints, and outline areas
where new data would be particularly valuable.Comment: 63p, uuencoded compressed postscript, 2/8 figs included, A&A Review
in press, request paper copies from [email protected], STScI 86
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
SARS-CoV-2 reservoir in post-acute sequelae of COVID-19 (PASC)
Millions of people are suffering from Long COVID or post-acute sequelae of COVID-19 (PASC). Several biological factors have emerged as potential drivers of PASC pathology. Some individuals with PASC may not fully clear the coronavirus SARS-CoV-2 after acute infection. Instead, replicating virus and/or viral RNA—potentially capable of being translated to produce viral proteins—persist in tissue as a ‘reservoir’. This reservoir could modulate host immune responses or release viral proteins into the circulation. Here we review studies that have identified SARS-CoV-2 RNA/protein or immune responses indicative of a SARS-CoV-2 reservoir in PASC samples. Mechanisms by which a SARS-CoV-2 reservoir may contribute to PASC pathology, including coagulation, microbiome and neuroimmune abnormalities, are delineated. We identify research priorities to guide the further study of a SARS-CoV-2 reservoir in PASC, with the goal that clinical trials of antivirals or other therapeutics with potential to clear a SARS-CoV-2 reservoir are accelerated
Gut Microbiota and Celiac Disease
Recent evidence regarding celiac disease has increasingly shown the role of innate immunity in triggering the immune response by stimulating the adaptive immune response and by mucosal damage. The interaction between the gut microbiota and the mucosal wall is mediated by the same receptors which can activate innate immunity. Thus, changes in gut microbiota may lead to activation of this inflammatory pathway. This paper is a review of the current knowledge regarding the relationship between celiac disease and gut microbiota. In fact, patients with celiac disease have a reduction in beneficial species and an increase in those potentially pathogenic as compared to healthy subjects. This dysbiosis is reduced, but might still remain, after a gluten-free diet. Thus, gut microbiota could play a significant role in the pathogenesis of celiac disease, as described by studies which link dysbiosis with the inflammatory milieu in celiac patients. The use of probiotics seems to reduce the inflammatory response and restore a normal proportion of beneficial bacteria in the gastrointestinal tract. Additional evidence is needed in order to better understand the role of gut microbiota in the pathogenesis of celiac disease, and the clinical impact and therapeutic use of probiotics in this setting