7,251 research outputs found
New thinking
The traditional practice of medicine provides an excellent model of our thinking behavior. A child is brought into the clinic by his mother. The child has a rash. The doctor thinks of a range of possibilities from food allergy to measles. The doctor then makes a judgement or diagnosis based on signs, symptoms, history, tests (to exclude other possibilities), environmental factors, etc. If the doctor judges the condition to be measles then the probable course of the illness is known, as are the possible complications and the traditional treatment. This is an excellent and effective system.peer-reviewe
How does diabetes cause coronary artery disease?
From the cardiologist’s viewpoint, diabetes increases the rate of development of coronary atheroma, increases the risk of a coronary thrombosis, and has a deleterious effect on the outcome of myocardial infarction. In this article the author describes the risk factors associated with diabetes and concentrate on ways which diabetes may accelerate atheroma.peer-reviewe
The direct teaching of thinking as a skill
The teaching of thinking as a skill is not tomorrow's dream but today's reality, claims one of the world's foremost experts on the topic. He describes his methods for teaching "the generalizable skill of thinking" - methods that have been used from the jungles of South America to the boardrooms of major corporations.peer-reviewe
Clustering of Local Group distances: publication bias or correlated measurements? V. Galactic rotation constants
As part of on an extensive data mining effort, we have compiled a database of
162 Galactic rotation speed measurements at (the solar Galactocentric
distance), . Published between 1927 and 2017 June, this represents
the most comprehensive set of values since the 1985 meta analysis
that led to the last revision of the International Astronomical Union's
recommended Galactic rotation constants. Although we do not find any compelling
evidence of the presence of `publication bias' in recent decades, we find clear
differences among the values and the ratios resulting
from the use of different tracer populations. Specifically, young tracers
(including OB and supergiant stars, masers, Cepheid variables, H{\sc ii}
regions, and young open clusters), as well as kinematic measurements of Sgr A*
near the Galactic Center, imply a significantly larger Galactic rotation speed
at the solar circle and a higher ratio (i.e., km s and km s kpc;
statistical uncertainties only) than any of the tracers dominating the Galaxy's
mass budget (i.e., field stars and the H{\sc i}/CO distributions). Using the
latter as most representative of the bulk of the Galaxy's matter distribution,
we arrive at an updated set of Galactic rotation constants, \Theta_0 = 225 \pm
3 \mbox{ (statistical)} \pm 10 \mbox{ (systematic) km s}^{-1}, R_0 = 8.3 \pm
0.2 \mbox{ (statistical)} \pm 0.4 \mbox{ (systematic) kpc}, and \Theta_0 /
R_0 = 27.12 \pm 0.39 \mbox{ (statistical)} \pm 1.78 \mbox{ (systematic) km
s}^{-1} \mbox{ kpc}^{-1}.Comment: 8 pages, 4 figures; ApJS, in pres
Clustering of Local Group distances: publication bias or correlated measurements? VII. A distance framework out to 100 Mpc
We consider the published distance moduli to the Fornax and Coma galaxy
clusters, with emphasis on the period since 1990. We have carefully homogenized
our catalogs of distance moduli onto the distance scale established in the
previous papers in this series. We assessed systematic differences associated
with the use of specific tracers, and discarded results based on application of
the Tully--Fisher relation and of globular cluster and planetary nebula
luminosity functions. We recommend `best' weighted relative distance moduli for
the Fornax and Coma clusters with respect to the Virgo cluster of mag and mag. The set of weighted mean distance moduli
(distances) we derived as most representative of the clusters' distances is,
\begin{eqnarray} (m-M)_0^{\rm Fornax} &=& 31.41 \pm 0.15 \mbox{ mag } (D =
19.1^{+1.4}_{-1.2} \mbox{ Mpc) and} \nonumber
&=& 31.21 \pm 0.28 \mbox{ mag } (D = 17.5^{+2.4}_{-2.2} \mbox{ Mpc)};
\nonumber \\ (m-M)_0^{\rm Coma} &=& 34.99 \pm 0.38 \mbox{ mag } (D =
99.5^{+19.0}_{-15.9} \mbox{ Mpc) and} \nonumber
&=& 34.78 \pm 0.27 \mbox{ mag } (D = 90.4^{+11.9}_{-10.6} \mbox{ Mpc)},
\nonumber \end{eqnarray} where the first value for each cluster is the result
of our analysis of the direct distance moduli, while the second modulus is
based on distance moduli relative to the Virgo cluster. The absolute and
relative distance moduli for both clusters are mutually consistent within the
uncertainties; the relative distance moduli yield shorter distances by
1. Lingering uncertainties in the underlying absolute distance
scale appear to have given rise to a systematic uncertainty on the order of
0.20 mag.Comment: 15 pages, 3 figures; accepted for publication in ApJ
Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud
Aiming at providing a firm mean distance estimate to the Small Magellanic
Cloud (SMC), and thus to place it within the internally consistent Local Group
distance framework we recently established, we compiled the current-largest
database of published distance estimates to the galaxy. Based on careful
statistical analysis, we derive mean distance estimates to the SMC using
eclipsing binary systems, variable stars, stellar population tracers, and star
cluster properties. Their weighted mean leads to a final recommendation for the
mean SMC distance of mag, where the
uncertainty represents the formal error. Systematic effects related to
lingering uncertainties in extinction corrections, our physical understanding
of the stellar tracers used, and the SMC's complex geometry---including its
significant line-of-sight depth, its irregular appearance which renders
definition of the galaxy's center uncertain, as well as its high inclination
and possibly warped disk---may contribute additional uncertainties possibly
exceeding 0.15--0.20 mag.Comment: 17 pages, 2 figures (emulateapj format); AJ, in pres
Clustering of Local Group distances: publication bias or correlated measurements? II. M31 and beyond
The accuracy of extragalactic distance measurements ultimately depends on
robust, high-precision determinations of the distances to the galaxies in the
local volume. Following our detailed study addressing possible publication bias
in the published distance determinations to the Large Magellanic Cloud (LMC),
here we extend our distance range of interest to include published distance
moduli to M31 and M33, as well as to a number of their well-known dwarf galaxy
companions. We aim at reaching consensus on the best, most homogeneous, and
internally most consistent set of Local Group distance moduli to adopt for
future, more general use based on the largest set of distance determinations to
individual Local Group galaxies available to date. Based on a careful,
statistically weighted combination of the main stellar population tracers
(Cepheids, RR Lyrae variables, and the magnitude of the tip of the red-giant
branch), we derive a recommended distance modulus to M31 of mag---adopting as our calibration an LMC distance modulus of
mag---and a fully internally consistent set of
benchmark distances to key galaxies in the local volume, enabling us to
establish a robust and unbiased, near-field extragalactic distance ladder.Comment: AJ, in press; 32 pages in AASTeX preprint format, 6 postscript
figures. For online database, see http://astro-expat.info/Data/pubbias.htm
A rare case of an idiopathic extraocular muscle abscess
Diplopia has a diverse range of ophthalmological, neurological, autoimmune, neoplastic and infectious causes. However it is very rare for an extraocular muscle abscess to occur. A skeletal muscle abscess usually occurs in the thigh and trunk muscles and is most commonly caused by Staphylococcus aureus.1
The purpose of this case report is to describe this condition we came across in our eye casualty department in a healthy teenager who presented with painful diplopia and this was due to a lateral rectus muscle abscess.
Complete resolution of the diplopia occurred by 6 weeks from starting treatment. The possible aetiologies and possible complications of such a condition are then
discussed.
An idiopathic extraocular muscle abscess is a rare condition which should be included in the differential diagnosis of a patient presenting with painful double vision.peer-reviewe
The changing face of cancer therapeutics improved : outcome and decreased toxicity with Molecular Targeted Drugs
The treatment of patients with cancer has largely involved the administration of cytotoxic drugs with narrow therapeutic indices, with little selectivity for cancer cells over normal proliferating cells. The primary exception to this has been the successful administration of hormonal manipulation to treat breast and prostate malignancies. The development of hormonal manipulation arose from the observation by Sir George Beatson that breast carcinomas improved after bilateral oophorectomy. This led to the use of Tamoxifen and more recently aromatase inhibitors and oestrogen receptor antagonists. These targeted therapeutics are characterised by their ability to induce selective tumour cell death and achieve patient benefit with low toxicity, and have had a significant impact on the outcome of patients with early and advanced oestrogen receptor positive breast cancer. Further advances in the understanding of tumour cell biology, the sequencing of the human genome, and the characterisation of the molecular differences between malignant and normal cells have, over the past two decades, resulted in the identification of a large number of critically important molecular targets. As with the identification of the importance of oestrogens and the oestrogen receptor, this has accelerated the development of molecularly targeted therapeutics and is rapidly revolutionising cancer medicine (Table 1). This brief review will describe some of the most important advances achieved and will attempt to predict what future cancer therapeutics will entail.peer-reviewe
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