216 research outputs found
A primary cutaneous adenoid-cystic carcinoma in a young woman. Differential diagnosis and clinical implications
Primary cutaneous adenoid-cystic carcinoma (PCACC) is a rare slow-growing neoplasm of disputed histogenesis characterized by a cribriform pattern at histology and local aggressive behaviour. Up to date about 60 cases of PCACC have been reported in the literature. This tumour is most common in the scalp, affects middle-aged and older individuals (mean age 59) and has predilection for women. We describe an unexpected case of PCACC in a 32-years-old woman referred to our clinic for a subcutaneous nodule in the scalp showing a slow growth and indolent course. The differential diagnosis and the clinical management of this PCACC patient, successfully treated with a wide local excision, are presented and discussed
Transient dust in warm debris disks - Detection of Fe-rich olivine grains
(Abridged) Debris disks trace remnant reservoirs of leftover planetesimals in
planetary systems. A handful of "warm" debris disks have been discovered in the
last years, where emission in excess starts in the mid-infrared. An interesting
subset within these warm debris disks are those where emission features are
detected in mid-IR spectra, which points towards the presence of warm
micron-sized dust grains. Given the ages of the host stars, the presence of
these grains is puzzling, and questions their origin and survival in time. This
study focuses on determining the mineralogy of the dust around 7 debris disks
with evidence for warm dust, based on Spitzer/IRS spectroscopic data, in order
to provide new insights into the origin of the dust grains. We present a new
radiative transfer code dedicated to SED modeling of optically thin disks. We
make use of this code on the SEDs of seven warm debris disks, in combination
with recent laboratory experiments on dust optical properties. We find that
most, if not all, debris disks in our sample are experiencing a transient
phase, suggesting a production of small dust grains on relatively short
timescales. From a mineralogical point of view, we find that enstatite grains
have small abundances compared to crystalline olivine grains. The main result
of our study is that we find evidences for Fe-rich crystalline olivine grains
(Fe / [Mg + Fe] ~ 0.2) for several debris disks. This finding contrasts with
studies of gas-rich protoplanetary disks. The presence of Fe-rich olivine
grains, and the overall differences between the mineralogy of dust in Class II
disks compared to debris disks suggest that the transient crystalline dust is
of a new generation. We discuss possible crystallization routes to explain our
results, and comment on the mechanisms that may be responsible for the
production of small dust grains
The Magellanic Clouds as a Template for the Study of Stellar Populations and Galaxy Interactions
The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJK s survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science
Anatomy of the Epidemiological Literature on the 2003 SARS Outbreaks in Hong Kong and Toronto: A Time-Stratified Review
Weijia Xing and colleagues reviewed the published epidemiological literature on SARS and show that less than a quarter of papers were published during the epidemic itself, suggesting that the research published lagged substantially behind the need for it
Low-mass pre--main-sequence stars in the Magellanic Clouds
[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar
stars form in very large numbers. Most attractive places for catching low-mass
star formation in the act are young stellar clusters and associations, still
(half-)embedded in star-forming regions. The low-mass stars in such regions are
still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature
of these objects and the contamination of their samples by the evolved
populations of the Galactic disk impose demanding observational techniques for
the detection of complete numbers of PMS stars in the Milky Way. The Magellanic
Clouds, the companion galaxies to our own, demonstrate an exceptional star
formation activity. The low extinction and stellar field contamination in
star-forming regions of these galaxies imply a more efficient detection of
low-mass PMS stars than in the Milky Way, but their distance from us make the
application of special detection techniques unfeasible. Nonetheless, imaging
with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS
stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of
such objects are identified as the low-mass stellar content of their
star-forming regions, changing completely our picture of young stellar systems
outside the Milky Way, and extending the extragalactic stellar IMF below the
persisting threshold of a few solar masses. This review presents the recent
developments in the investigation of PMS stars in the Magellanic Clouds, with
special focus on the limitations by single-epoch photometry that can only be
circumvented by the detailed study of the observable behavior of these stars in
the color-magnitude diagram. The achieved characterization of the low-mass PMS
stars in the Magellanic Clouds allowed thus a more comprehensive understanding
of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4
figures. Accepted for publication in Space Science Review
Herschel images of Fomalhaut. An extrasolar Kuiper Belt at the height of its dynamical activity
Fomalhaut is a young, nearby star that is suspected to harbor an infant
planetary system, interspersed with one or more belts of dusty debris. We
present far-infrared images obtained with the Herschel Space Observatory with
an angular resolution between 5.7 and 36.7 arcsec at wavelengths between 70 and
500 micrometer. The images show the main debris belt in great detail. Even at
high spatial resolution, the belt appears smooth. The region in between the
belt and the central star is not devoid of material; thermal emission is
observed here as well. Also at the location of the star, excess emission is
detected.
We use a dynamical model together with radiative-transfer tools to derive the
parameters of the debris disk. We include detailed models of the interaction of
the dust grains with radiation, for both the radiation pressure and the
temperature determination. Comparing these models to the spatially resolved
temperature information contained in the images allows us to place strong
constraints on the presence of grains that will be blown out of the system by
radiation pressure. We use this to derive the dynamical parameters of the
system.
The appearance of the belt points towards a remarkably active system in which
dust grains are produced at a very high rate by a collisional cascade in a
narrow region filled with dynamically excited planetesimals. Dust particles
with sizes below the blow-out size are abundantly present. The equivalent of
2000 one-km-sized comets are destroyed every day, out of a cometary reservoir
amounting to 110 Earth masses. From comparison of their scattering and thermal
properties, we find evidence that the dust grains are fluffy aggregates, which
indicates a cometary origin. The excess emission at the location of the star
may be produced by hot dust with a range of temperatures, but may also be due
to gaseous free-free emission from a stellar wind.Comment: 9 pages, 6 figure
Combined aerobic and resistance exercise training decreases peripheral but not central artery wall thickness in subjects with type 2 diabetes
Objective
Little is known about the impact of exercise training on conduit artery wall thickness in type 2 diabetes. We examined the local and systemic impact of exercise training on superficial femoral (SFA), brachial (BA), and carotid artery (CA) wall thickness in type 2 diabetes patients and controls.
Methods
Twenty patients with type 2 diabetes and 10 age- and sex-matched controls performed an 8-week training study involving lower limb-based combined aerobic and resistance exercise training. We examined the SFA to study the local effect of exercise, and also the systemic impact of lower limb-based exercise training on peripheral (i.e. BA) and central (i.e. CA) arteries. Wall thickness (WT), diameter and wall:lumen(W:L)-ratios were examined using automated edge detection of ultrasound images.
Results
Exercise training did not alter SFA or CA diameter in type 2 diabetes or controls (all P > 0.05). BA diameter was increased after training in type 2 diabetes, but not in controls. Exercise training decreased WT and W:L ratio in the SFA and BA, but not in CA in type 2 diabetes. Training did not alter WT or W:L ratio in controls (P > 0.05).
Conclusion
Lower limb-dominant exercise training causes remodelling of peripheral arteries, supplying active and inactive vascular beds, but not central arteries in type 2 diabetes
Secondary prevention of heart disease – knowledge among cardiologists and Ω-3 (Omega-3) fatty acid prescribing behaviors in Karachi, Pakistan
<p>Abstract</p> <p>Background</p> <p>The use of omega-3 fatty acids is a currently proven strategy for secondary prevention of heart disease. The prescription practices for this important nutraceutical is not currently known. It is imperative to assess the knowledge of cardiologists regarding the benefits of omega-3 fatty acids and to determine the frequency of its prescription. The aim of the study was to determine the practices and associations of dietary fish prescribing among cardiologists of Karachi and to assess their knowledge of fish oil supplementation and attitudes toward dietary practices.</p> <p>Methods</p> <p>A cross sectional survey was conducted during the period of January to March, 2008. A self report questionnaire was employed. All practicing cardiologists of Karachi were included in the study. Multiple logistic regression analysis was performed to determine the independent factors associated with high fish prescribers.</p> <p>Results</p> <p>The sample comprised of a total of 163 cardiologists practicing in Karachi, Pakistan. Most (73.6%) of the cardiologists fell in the age range of 28 – 45 years and were male (90.8%). High fish prescribers only comprised 36.2% of the respondents. After adjusting for age and gender, multivariate analysis revealed that only the variable of knowledge about fish oil's role in reducing sudden cardiac death was independently associated with high fish prescribers OR = 6.38 [95% CI 2.58–15.78].</p> <p>Conclusion</p> <p>The level of knowledge about the benefits of omega-3 fatty acids is high and the cardiologists harbor a favorable attitude towards dispensing dietary fish advice. However, the prescription practices are less than optimal and not concordant with recommendations of organisations such as the American Heart Association and National Heart Foundation of Australia. The knowledge of prevention of sudden cardiac death in CVD patients has been identified as an important predictor of high fish prescription. This particular life-saving property of omega-3 fatty acids should be the focus of any implemented educational strategy targeted to improve secondary CVD prevention via omega-3 fatty acid supplementation.</p
A Proposed Taxonomy of Anaerobic Fungi (Class Neocallimastigomycetes) Suitable for Large-Scale Sequence-Based Community Structure Analysis
Anaerobic fungi are key players in the breakdown of fibrous plant material in the rumen, but not much is known about the composition and stability of fungal communities in ruminants. We analyzed anaerobic fungi in 53 rumen samples from farmed sheep (4 different flocks), cattle, and deer feeding on a variety of diets. Denaturing gradient gel electrophoresis fingerprinting of the internal transcribed spacer 1 (ITS1) region of the rrn operon revealed a high diversity of anaerobic fungal phylotypes across all samples. Clone libraries of the ITS1 region were constructed from DNA from 11 rumen samples that had distinctly different fungal communities. A total of 417 new sequences were generated to expand the number and diversity of ITS1 sequences available. Major phylogenetic groups of anaerobic fungi in New Zealand ruminants belonged to the genera Piromyces, Neocallimastix, Caecomyces and Orpinomyces. In addition, sequences forming four novel clades were obtained, which may represent so far undetected genera or species of anaerobic fungi. We propose a revised phylogeny and pragmatic taxonomy for anaerobic fungi, which was tested and proved suitable for analysis of datasets stemming from high-throughput next-generation sequencing methods. Comparing our revised taxonomy to the taxonomic assignment of sequences deposited in the GenBank database, we believe that >29% of ITS1 sequences derived from anaerobic fungal isolates or clones are misnamed at the genus level
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