33 research outputs found
Analyzing redshift surveys to measure the power spectrum on large scales
Upcoming large redshift surveys potentially allow precision measurements of
the galaxy power spectrum. To accurately measure P(k) on the largest scales,
comparable to the depth of the survey, it is crucial that finite volume effects
are accurately corrected for in the data analysis. Here we derive analytic
expressions for the one such effect that has not previously been worked out
exactly: that of the so-called integral constraint. We also show that for data
analysis methods based on counts in cells, multiple constraints can be included
via simple matrix operations, thereby rendering the results less sensitive to
galactic extinction and misestimates of the shape of the radial selection
function.Comment: Mostly superseded by astro-ph/9708020; from 5/5-97. 10 pages, with 1
figure included. More detailed treatment at
http://www.sns.ias.edu/~max/galpower.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/galpower.html (faster from Europe) or
from [email protected]
Angiomyofibroblastoma of the spermatic cord: a case report
<p>Abstract</p> <p>Introduction</p> <p>Angiomyofibroblastoma is a benign soft tissue tumor with tendency to arise in the vulva.</p> <p>Case presentation</p> <p>We report a 36-year-old Greek Caucasian man presenting with a left inguinal painless mass. This is the second case of angiomyofibroblastoma of the spermatic cord. At operation, a 4.5 cm well-circumscribed solid tumor was found adherent to the spermatic cord. The tumor consisted of spindle-shaped cells proliferating in short fascicles between numerous medium-sized blood vessels with thin and hyalinized walls. Neoplastic cells had eosinophilic cytoplasm with neither mitotic figures nor nuclear atypia. The stroma included abundant mast cells and few mature lypocytes. Immunostaining showed positivity for vimentin, CD34, desmin and smooth muscle actin. Our patient was treated by simple excision and was followed up for five years with clinical examination and ultrasonography, revealing no evidence of local recurrence or metastasis.</p> <p>Conclusion</p> <p>This unusual neoplasm should be distinguished from aggressive angiomyxoma and other myxoid malignant tumors with widespread metastatic potential.</p
Breakdown of the adiabatic limit in low dimensional gapless systems
It is generally believed that a generic system can be reversibly transformed
from one state into another by sufficiently slow change of parameters. A
standard argument favoring this assertion is based on a possibility to expand
the energy or the entropy of the system into the Taylor series in the ramp
speed. Here we show that this argumentation is only valid in high enough
dimensions and can break down in low-dimensional gapless systems. We identify
three generic regimes of a system response to a slow ramp: (A) mean-field, (B)
non-analytic, and (C) non-adiabatic. In the last regime the limits of the ramp
speed going to zero and the system size going to infinity do not commute and
the adiabatic process does not exist in the thermodynamic limit. We support our
results by numerical simulations. Our findings can be relevant to
condensed-matter, atomic physics, quantum computing, quantum optics, cosmology
and others.Comment: 11 pages, 5 figures, to appear in Nature Physics (originally
submitted version
Cluster Lenses
Clusters of galaxies are the most recently assembled, massive, bound
structures in the Universe. As predicted by General Relativity, given their
masses, clusters strongly deform space-time in their vicinity. Clusters act as
some of the most powerful gravitational lenses in the Universe. Light rays
traversing through clusters from distant sources are hence deflected, and the
resulting images of these distant objects therefore appear distorted and
magnified. Lensing by clusters occurs in two regimes, each with unique
observational signatures. The strong lensing regime is characterized by effects
readily seen by eye, namely, the production of giant arcs, multiple-images, and
arclets. The weak lensing regime is characterized by small deformations in the
shapes of background galaxies only detectable statistically. Cluster lenses
have been exploited successfully to address several important current questions
in cosmology: (i) the study of the lens(es) - understanding cluster mass
distributions and issues pertaining to cluster formation and evolution, as well
as constraining the nature of dark matter; (ii) the study of the lensed objects
- probing the properties of the background lensed galaxy population - which is
statistically at higher redshifts and of lower intrinsic luminosity thus
enabling the probing of galaxy formation at the earliest times right up to the
Dark Ages; and (iii) the study of the geometry of the Universe - as the
strength of lensing depends on the ratios of angular diameter distances between
the lens, source and observer, lens deflections are sensitive to the value of
cosmological parameters and offer a powerful geometric tool to probe Dark
Energy. In this review, we present the basics of cluster lensing and provide a
current status report of the field.Comment: About 120 pages - Published in Open Access at:
http://www.springerlink.com/content/j183018170485723/ . arXiv admin note:
text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author
The Formation and Evolution of the First Massive Black Holes
The first massive astrophysical black holes likely formed at high redshifts
(z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations.
These black holes grow by mergers and gas accretion, evolve into the population
of bright quasars observed at lower redshifts, and eventually leave the
supermassive black hole remnants that are ubiquitous at the centers of galaxies
in the nearby universe. The astrophysical processes responsible for the
formation of the earliest seed black holes are poorly understood. The purpose
of this review is threefold: (1) to describe theoretical expectations for the
formation and growth of the earliest black holes within the general paradigm of
hierarchical cold dark matter cosmologies, (2) to summarize several relevant
recent observations that have implications for the formation of the earliest
black holes, and (3) to look into the future and assess the power of
forthcoming observations to probe the physics of the first active galactic
nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant
Universe", Ed. A. J. Barger, Kluwer Academic Publisher
Modeling the accretion history of supermassive black holes
There is overwhelming evidence for the presence of supermassive black holes
(SMBHs) in the centers of most nearby galaxies. The mass estimates for these
remnant black holes from the stellar kinematics of local galaxies and the
quasar phenomenon at high redshifts point to the presence of assembled SMBHs.
The accretion history of SMBHs can be reconstructed using observations at high
and low redshifts as model constraints. Observations of galaxies and quasars in
the submillimeter, infrared, optical, and X-ray wavebands are used as
constraints, along with data from the demography of local black holes.
Theoretical modeling of the growth of black hole mass with cosmic time has been
pursued thus far in two distinct directions: a phenomenological approach that
utilizes observations in various wavebands, and a semi-analytic approach that
starts with a theoretical framework and a set of assumptions with a view to
matching observations. Both techniques have been pursued in the context of the
standard paradigm for structure formation in a Cold Dark Matter dominated
universe. Here, we examine the key issues and uncertainties in the theoretical
understanding of the growth of SMBHs.Comment: 19 pages, 4 figures, to appear as Chapter 4 in "Supermassive Black
Holes in the Distant Universe" (2004), ed. A. J. Barger, Kluwer Academic
Publishers, in pres
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Long COVID research: an update from the PHOSP-COVID Scientific Summit
The severity of acute SARS-CoV-2 infection has decreased with the introduction of public health policies, vaccination, improved management of acute disease, and a degree of protective immunity in those who have survived past infection. However, in the wake of the pandemic, post-acute sequelae of COVID-19—referred to as long COVID—have emerged. The UK National Institute for Health and Care Excellence (NICE) describes long COVID as a condition in which signs and symptoms continue or develop after acute COVID-19 (>4 weeks), including ongoing symptomatic COVID-19 and post-COVID-19 syndrome (≥12 weeks).PHOSP-COVID is jointly funded by a grant from the Medical Research Council UK Research and Innovation and the Department of Health and Social Care through the National Institute for Health Research (NIHR) rapid response panel to tackle COVID-19 (MR/V027859/1 and COV0319)
The PSCz catalogue
We present the catalogue, mask, redshift data and selection function for the
PSCz survey of 15411 IRAS galaxies across 84% of the sky. Most of the IRAS data
is taken from the Point Source Catalog, but this has been supplemented and
corrected in various ways to improve the completeness and uniformity. We
quantify the known imperfections in the catalogue, and we assess the overall
uniformity, completeness and data quality. We find that overall the catalogue
is complete and uniform to within a few percent at high latitudes and 10% at
low latitudes. Ancillary information, access details, guidelines and caveats
for using the catalogue are given.Comment: 10 pages, submitted to MNRAS Oct 1999, accepted 8 March 2000.
Includes details for data acces