253 research outputs found
Computed tomography and magnetic resonance imaging of desmoplastic fibroma with simultaneous manifestation in two unusual locations: a case report
<p>Abstract</p> <p>Introduction</p> <p>Desmoplastic fibroma is an extremely rare primary benign bone tumor. It occurs most often in the mandible, followed by the femur and pelvis. To the best of our knowledge, fewer than 200 cases have been described in the published literature. Furthermore, this case is the first report of desmoplastic fibroma with simultaneous presentation in two different locations.</p> <p>Case presentation</p> <p>We present an unusual case of desmoplastic fibroma in a 56-year-old Caucasian man, who presented to our hospital with lumbar pain. Computed tomography and magnetic resonance imaging were performed, demonstrating two lytic expansile lesions affecting both his left iliac bone and his left sacral wing. Curettage and cortical-cancellous grafting was performed, followed by postoperative computed tomography and magnetic resonance imaging.</p> <p>Conclusion</p> <p>Desmoplastic fibroma with unusual and simultaneous manifestations in two different locations has never been reported previously to the best of our knowledge. The purpose of this case report is to present the computed tomography and magnetic resonance imaging features of this rare tumor before and after the surgical treatment. Furthermore, the radiological findings with the description of the characteristics and the clinical presentation of this rare tumor, contribute to the wide spectrum of manifestations of this tumor, in order to recognize it and to have the appropriate management.</p
Formation of Supermassive Black Holes
Evidence shows that massive black holes reside in most local galaxies.
Studies have also established a number of relations between the MBH mass and
properties of the host galaxy such as bulge mass and velocity dispersion. These
results suggest that central MBHs, while much less massive than the host (~
0.1%), are linked to the evolution of galactic structure. In hierarchical
cosmologies, a single big galaxy today can be traced back to the stage when it
was split up in hundreds of smaller components. Did MBH seeds form with the
same efficiency in small proto-galaxies, or did their formation had to await
the buildup of substantial galaxies with deeper potential wells? I briefly
review here some of the physical processes that are conducive to the evolution
of the massive black hole population. I will discuss black hole formation
processes for `seed' black holes that are likely to place at early cosmic
epochs, and possible observational tests of these scenarios.Comment: To appear in The Astronomy and Astrophysics Review. The final
publication is available at http://www.springerlink.co
A Rare Periosteal Diaphyseal Lesion of the Ulna
Periosteal lesions of the ulna diaphysis are rare, include a wide spectrum of tumors, and may cause considerable diagnostic problems. Surgical treatment may vary widely, based on an accurate diagnosis. We present the case of a periosteal, extraskeletal low grade myxoid chondrosarcoma of the ulna diaphysis. The surgical therapy included an en-bloc resection with allograft reconstruction. The patient showed a favorable outcome. Careful preoperative evaluation and planning are imperative to obtain a satisfactory oncological and functional outcome, especially with uncommon tumor presentations at rare locations
On the Importance of Countergradients for the Development of Retinotopy: Insights from a Generalised Gierer Model
During the development of the topographic map from vertebrate retina to superior colliculus (SC), EphA receptors are expressed in a gradient along the nasotemporal retinal axis. Their ligands, ephrin-As, are expressed in a gradient along the rostrocaudal axis of the SC. Countergradients of ephrin-As in the retina and EphAs in the SC are also expressed. Disruption of any of these gradients leads to mapping errors. Gierer's (1981) model, which uses well-matched pairs of gradients and countergradients to establish the mapping, can account for the formation of wild type maps, but not the double maps found in EphA knock-in experiments. I show that these maps can be explained by models, such as Gierer's (1983), which have gradients and no countergradients, together with a powerful compensatory mechanism that helps to distribute connections evenly over the target region. However, this type of model cannot explain mapping errors found when the countergradients are knocked out partially. I examine the relative importance of countergradients as against compensatory mechanisms by generalising Gierer's (1983) model so that the strength of compensation is adjustable. Either matching gradients and countergradients alone or poorly matching gradients and countergradients together with a strong compensatory mechanism are sufficient to establish an ordered mapping. With a weaker compensatory mechanism, gradients without countergradients lead to a poorer map, but the addition of countergradients improves the mapping. This model produces the double maps in simulated EphA knock-in experiments and a map consistent with the Math5 knock-out phenotype. Simulations of a set of phenotypes from the literature substantiate the finding that countergradients and compensation can be traded off against each other to give similar maps. I conclude that a successful model of retinotopy should contain countergradients and some form of compensation mechanism, but not in the strong form put forward by Gierer
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
On the cosmic evolution of the scaling relations between black holes and their host galaxies: Broad Line AGN in the zCOSMOS survey
(Abriged) We report on the measurement of the rest frame K-band luminosity
and total stellar mass of the hosts of 89 broad line Active Galactic Nuclei
detected in the zCOSMOS survey in the redshift range 1<z<2.2. The unprecedented
multiwavelength coverage of the survey field allows us to disentangle the
emission of the host galaxy from that of the nuclear black hole in their
Spectral Energy Distributions. We derive an estimate of black hole masses
through the analysis of the broad Mg II emission lines observed in the
medium-resolution spectra taken with VIMOS/VLT as part of the zCOSMOS project.
We found that, as compared to the local value, the average black hole to host
galaxy mass ratio appears to evolve positively with redshift, with a best fit
evolution of the form (1+z)^{0.68 \pm0.12 +0.6 -0.3}, where the large
asymmetric systematic errors stem from the uncertainties in the choice of IMF,
in the calibration of the virial relation used to estimate BH masses and in the
mean QSO SED adopted. A thorough analysis of observational biases induced by
intrinsic scatter in the scaling relations reinforces the conclusion that an
evolution of the MBH-M* relation must ensue for actively growing black holes at
early times: either its overall normalization, or its intrinsic scatter (or
both) appear to increase with redshift. This can be interpreted as signature of
either a more rapid growth of supermassive black holes at high redshift, a
change of structural properties of AGN hosts at earlier times, or a significant
mismatch between the typical growth times of nuclear black holes and host
galaxies.Comment: 47 pages, 8 figures. Accepted for publication in Ap
Supermassive black holes do not correlate with galaxy disks or pseudobulges
The masses of supermassive black holes are known to correlate with the
properties of the bulge components of their host galaxies. In contrast, they
appear not to correlate with galaxy disks. Disk-grown pseudobulges are
intermediate in properties between bulges and disks. It has been unclear
whether they do or do not correlate with black holes in the same way that
bulges do, because too few pseudobulges were classified to provide a clear
result. At stake are conclusions about which parts of galaxies coevolve with
black holes, possibly by being regulated by energy feedback from black holes.
Here we report pseudobulge classifications for galaxies with dynamically
detected black holes and combine them with recent measurements of velocity
dispersions in the biggest bulgeless galaxies. These data confirm that black
holes do not correlate with disks and show that they correlate little or not at
all with pseudobulges. We suggest that there are two different modes of black
hole feeding. Black holes in bulges grow rapidly to high masses when mergers
drive gas infall that feeds quasar-like events. In contrast, small black holes
in bulgeless galaxies and galaxies with pseudobulges grow as low-level
Seyferts. Growth of the former is driven by global processes, so the biggest
black holes coevolve with bulges, but growth of the latter is driven locally
and stochastically, and they do not coevolve with disks and pseudobulges.Comment: 6 pages, 3 Postscript figures, 1 table; to appear in Nature (20
January 2011
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
Pre-ART Levels of Inflammation and Coagulation Markers Are Strong Predictors of Death in a South African Cohort with Advanced HIV Disease
BACKGROUND: Levels of high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), and D-dimer predict mortality in HIV patients on antiretroviral therapy (ART) with relatively preserved CD4+ T cell counts. We hypothesized that elevated pre-ART levels of these markers among patients with advanced HIV would be associated with an increased risk of death following the initiation of ART. METHODS: Pre-ART plasma from patients with advanced HIV in South Africa was used to measure hsCRP, IL-6 and D-dimer. Using a nested case-control study design, the biomarkers were measured for 187 deaths and two controls matched on age, sex, clinical site, follow-up time and CD4+ cell counts. Odds ratios were estimated using conditional logistic regression. In addition, for a random sample of 100 patients, biomarkers were measured at baseline and 6 months following randomization to determine whether ART altered their levels. RESULTS: Median baseline biomarkers levels for cases and controls, respectively, were 11.25 vs. 3.6 mg/L for hsCRP, 1.41 vs. 0.98 mg/L for D-dimer, and 9.02 vs. 4.20 pg/mL for IL-6 (all p<0.0001). Adjusted odds ratios for the highest versus lowest quartile of baseline biomarker levels were 3.5 (95% CI: 1.9-6.7) for hsCRP, 2.6 (95%CI 1.4-4.9) for D-dimer, and 3.8 (95% CI: 1.8-7.8) for IL-6. These associations were stronger for deaths that occurred more proximal to the biomarker measurements. Levels of D-dimer and IL-6, but not hsCRP, were significantly lower at month 6 after commencing ART compared to baseline (p<0.0001). CONCLUSIONS: Among patients with advanced HIV disease, elevated pre-ART levels of hsCRP, IL-6 and D-dimer are strongly associated with early mortality after commencing ART. Elevated levels of inflammatory and coagulation biomarkers may identify patients who may benefit from aggressive clinical monitoring after commencing ART. Further investigation of strategies to reduce biomarkers of inflammation and coagulation in patients with advanced HIV disease is warranted. TRIAL REGISTRATION: Parent study: ClinicalTrials.gov NCT00342355
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