2,551 research outputs found
Another Look at Confidence Intervals: Proposal for a More Relevant and Transparent Approach
The behaviors of various confidence/credible interval constructions are
explored, particularly in the region of low statistics where methods diverge
most. We highlight a number of challenges, such as the treatment of nuisance
parameters, and common misconceptions associated with such constructions. An
informal survey of the literature suggests that confidence intervals are not
always defined in relevant ways and are too often misinterpreted and/or
misapplied. This can lead to seemingly paradoxical behaviours and flawed
comparisons regarding the relevance of experimental results. We therefore
conclude that there is a need for a more pragmatic strategy which recognizes
that, while it is critical to objectively convey the information content of the
data, there is also a strong desire to derive bounds on models and a natural
instinct to interpret things this way. Accordingly, we attempt to put aside
philosophical biases in favor of a practical view to propose a more transparent
and self-consistent approach that better addresses these issues.Comment: 23 pages, 11 figure
Detection of Bacterial Lipopolysaccharides of Escherichia coli by Direct Analysis in Real Time/Time-of-Flight Mass Spectrometry
Lipopolysaccharides (LPS) are a major component of the outer membrane in Gram-negative bacteria species and are responsible for toxicity caused by organisms such as Escherichia coli (E.coli). Conventional methods for characterizing LPS utilize mass spectrometry, particularly matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) and liquid chromatography mass spectrometry (LC-MS). Although these are successful in analyzing intact LPS molecules, they can be time-consuming. Other mass spectrometry techniques, such as direct analysis in real time/time-of-flight mass spectrometry (DART-TOF-MS) could also be helpful in the rapid analysis of LPS molecules without sample extraction procedures. This research focuses on the application of a DART-TOF-MS method to rapidly identify LPS molecules from E. coli as well as an analysis of LPS extracts generated using a commercial LPS extraction kit by gas chromatography-flame ionization detection (GC-FID). It was determined that DART-TOF-MS allows for the direct detection of LPS-specific fatty acids from solutions containing intact E.coli cells. Finally, the GC-FID based evaluation of the commercial LPS extraction kit showed that resulting extracts were enriched in LPS-specific fatty acids compared to intracellular/membrane fatty acids
The First Direct Distance and Luminosity Determination for a Self-Luminous Giant Exoplanet: The Trigonometric Parallax to 2MASS1207334-393254Ab
We present the first trigonometric parallax and distance for a young
planetary mass object. A likely TW Hya cluster member, 2MASSW J1207334-393254Ab
(hereafter 2M1207Ab) is an M8 brown dwarf with a mid to late L type planetary
mass companion. Recent observations of spectral variability have uncovered
clear signs of disk accretion and outflow, constraining the age of the system
to <10 Myr. Because of its late spectral type and the clearly youthful nature
of the system, 2M1207b is very likely a planetary mass object. We have measured
the first accurate distance and luminosity for a self-luminous planetary mass
object. Our parallax measurements are accurate to <2 mas (1sigma) for 2M1207Ab.
With 11 total epochs of data taken from January 2006 through April 2 007 (475
images for 2M1207Ab), we determine a distance of 58.8+-7.0 pc (17.0{+2.3}{-1.8}
mas, 1.28sigma) to 2M1207Ab and a calculated luminosity of 0.68-2.2x10^-5 Lsun
for 2M1207b. Hence 2M1207Ab is a clear member of the TW Hya cluster in terms of
its distance, proper motions, and youthful nature. However, as previously noted
by Mohanty and co-workers, 2M1207b's luminosity appears low compared to its
temperature according to evolutionary models.Comment: 12 pages, 3 figures, accepted to ApJ Letter
Informed Consent - Balance zwischen Patientenschutz und Forschungsinteressen
Forschungsethische Debatten haben sich in den letzten Jahren häufig der Frage gewidmet,
ob Ausnahmen bei der strikten Forderung nach individueller Einwilligung
des Patienten zulässig oder gar geboten sind. Einige Studiendesigns mit solchen Ausnahmeregelungen
werden im Folgenden zur Diskussion vorgestellt
The very nearby M/T dwarf binary SCR 1845-6357
The recently discovered star SCR 1845-6357 is the first late M/T dwarf binary
discovered. SCR 1845 is a particular object due to its tight orbit (currently
around 4 AU) and its proximity to the Sun (3.85 pc). We present spatially
resolved VLT/NACO images and low resolution spectra of SCR 1845 in the J, H and
K near-infrared bands. Since the T dwarf companion, SCR 1845B, is so close to
the primary SCR 1845A, orbital motion is evident even within a year. Following
the orbital motion, the binary's mass can be measured accurately within a
decade, making SCR 1845B a key T-dwarf mass-luminosity calibrator. The NIR
spectra allow for accurate determination of spectral type and also for rough
estimates of the object's physical parameters. The spectral type of SCR 1845B
is determined by direct comparison of the flux calibrated JHK spectra with T
dwarf standard template spectra and also by NIR spectral indices obtained from
synthetic photometry. Constrained values for surface gravity, effective
temperature and metallicity are derived by comparison with model spectra. Our
data prove that SCR 1845B is a brown dwarf of spectral type T6 that is
co-moving with and therefore gravitationally bound to the M8.5 primary. Fitting
the NIR spectrum of SCR 1845B to model spectra yields an effective temperature
of about 950K and a surface gravity log(g)=5.1 (cgs) assuming solar
metallicity. Mass and age of SCR 1845B are in the range 40 to 50 Jupiter masses
and 1.8 to 3.1 Gyr.Comment: 5 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
Complications of Cushing's syndrome: state of the art
Cushing's syndrome is a serious endocrine disease caused by chronic, autonomous, and excessive secretion of cortisol. The syndrome is associated with increased mortality and impaired quality of life because of the occurrence of comorbidities. These clinical complications include metabolic syndrome, consisting of systemic arterial hypertension, visceral obesity, impairment of glucose metabolism, and dyslipidaemia; musculoskeletal disorders, such as myopathy, osteoporosis, and skeletal fractures; neuropsychiatric disorders, such as impairment of cognitive function, depression, or mania; impairment of reproductive and sexual function; and dermatological manifestations, mainly represented by acne, hirsutism, and alopecia. Hypertension in patients with Cushing's syndrome has a multifactorial pathogenesis and contributes to the increased risk for myocardial infarction, cardiac failure, or stroke, which are the most common causes of death; risks of these outcomes are exacerbated by a prothrombotic diathesis and hypokalaemia. Neuropsychiatric disorders can be responsible for suicide. Immune disorders are common; immunosuppression during active disease causes susceptibility to infections, possibly complicated by sepsis, an important cause of death, whereas immune rebound after disease remission can exacerbate underlying autoimmune diseases. Prompt treatment of cortisol excess and specific treatments of comorbidities are crucial to prevent serious clinical complications and reduce the mortality associated with Cushing's syndrome
Memory Loss, Behavioral Changes, and Slurred Speech in a 49-Year-Old Man
A 49-year-old man presented with slurred speech, memory loss, and behavioral changes. His clinical course was marked by decline in functional status and cognition. He had poorly controlled hypertension and hyperlipidemia. Neuroimaging was remarkable for multiple subcortical white matter lesions. We discuss the diagnostic and therapeutic approach of rapidly progressing cognitive decline in the given clinical setting
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