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"Centaurs."
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Centaurs
Explore centaurs and the dangers they were thought to pose to both themselves and to humans.
Book
A dense ring of the trans-Neptunian object Quaoar outside its Roche limit
Planetary rings are observed not only around giant planets
1
, but also around small bodies such as the Centaur Chariklo
2
and the dwarf planet Haumea
3
. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius
4
of 555 km and possesses a roughly 80-km satellite
5
(Weywot) that orbits at 24 Quaoar radii
6
,
7
. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar’s classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments
8
, can maintain a ring far away from the body. Moreover, Quaoar’s ring orbits close to the 1/3 spin–orbit resonance
9
with Quaoar, a property shared by Chariklo’s
2
,
10
,
11
and Haumea’s
3
rings, suggesting that this resonance plays a key role in ring confinement for small bodies.
The authors report observations of a dense and inhomogeneous ring at a surprisingly large distance from the trans-Neptunian body Quaoar.
Journal Article
Centaur rising
In 1965, a year after Arianne thinks she sees a shooting star land in the fields surrounding her family's horse farm, a baby centaur is born and the family, already under scrutiny because Arianne's six-year-old brother has birth defects, struggles to keep the colt a secret.
BOOK
LCROSS Cratering Experiment
As its detached upper-stage launch vehicle collided with the surface, instruments on the trailing Lunar Crater Observation and Sensing Satellite (LCROSS) Shepherding Spacecraft monitored the impact and ejecta. The faint impact flash in visible wavelengths and thermal signature imaged in the mid-infrared together indicate a low-density surface layer. The evolving spectra reveal not only OH within sunlit ejecta but also other volatile species. As the Shepherding Spacecraft approached the surface, it imaged a 25- to-30-meter-diameter crater and evidence of a high-angle ballistic ejecta plume still in the process of returning to the surface--an evolution attributed to the nature of the impactor.
Journal Article
Centaur school
\"Demon has always counted on his magical medicine box to help him cure the sick beasts on Mount Olympus. But Chiron, his new healing master, insists Demon learn to find the cures on his own. Demon's new skills are soon put to the test when he must save an ailing phoenix--or face the wrath of its fiery guards!\"-- Provided by publisher.
Book
Evaluation of a high-sensitivity cardiac troponin I assay compared to a first-generation cardiac troponin I assay in Doberman Pinschers with and without dilated cardiomyopathy
Abstract
Background
Echocardiography and 24-hour ECG are the gold standard tests to diagnose dilated cardiomyopathy (DCM) in Doberman Pinschers (DP), but myocardial damage might be detected earlier using a high-sensitivity cardiac troponin I (hs-cTnI) assay.
Objective
To evaluate and compare an hs-cTnI assay (Advia Centaur TnI-Ultra assay) with a conventional cTnI assay in DP with different stages of DCM and in healthy DP.
Animals
Three hundred forty-five examinations from 162 DP with and 179 DP without DCM.
Methods
Prospective longitudinal study. Dogs were allocated into 6 groups based on echocardiographic and 24-hour ECG criteria: (1) healthy group (179 dogs), (2) last-normal group (29 dogs), which included dogs that were considered to be healthy at the time of their examination but were assigned to the last-normal group retrospectively when DCM was diagnosed at their next examination within 1.5 years, (3) only arrhythmias (45 dogs, 119 examinations), (4) only echocardiographic changes (24 dogs, 61 examinations), (5) echocardiographic changes with ventricular premature complexes (41 dogs, 100 examinations), and (6) decompensated (23 dogs, 36 examinations). Hs-cTnI and conventional cTnI concentration measurements were performed and compared.
Results
A cutoff value of hs-cTnI concentration >0.113 ng/mL had a sensitivity of 81.2% and a specificity of 73.2% to identify the presence of DCM. The conventional cTnI assay showed a similar test performance, but the hs-cTnI assay identified more dogs (21/29 dogs, 72%) in the last-normal group compared to the conventional cTnI test (18/29 dogs, 62%).
Conclusions and Clinical Importance
The hs-cTnI is an additional test with good potential to identify early DCM.
Journal Article
Centaur and giant planet crossing populations: origin and distribution
The current giant planet region is a transitional zone where transneptunian objects (TNOs) cross in their way to becoming Jupiter Family Comets. Their dynamical behavior is conditioned by the intrinsic dynamical features of TNOs and also by the encounters with the giant planets. We address the Giant Planet Crossing (GPC) population (those objects with 5.2 au 100km and ∼108 with D>1km in the current population. The contribution from other sources is considered negligible. The mean lifetime in the Centaur zone is 7.2 Myr, while the mean lifetime of SDOs in the GPC zone is of 68 Myr. The latter is dependent on the initial inclination, being the ones with high inclinations the ones that survive the longest in the GPC zone. There is also a correlation of lifetime with perihelion distance, where greater perihelion leads to longer lifetime. The dynamical evolution of observed GPCs is different for prograde and retrograde objects. Retrograde GPCs have lower median lifetime than prograde ones, thus experiencing a comparatively faster evolution. However, it is probable that this faster evolution is due to the fact that the majority of retrograde GPCs have low perihelion values and then, lower lifetimes.
Journal Article
A Uranian Trojan and the Frequency of Temporary Giant-Planet Co-Orbitals
Trojan objects share a planet's orbit, never straying far from the triangular Lagrangian points, 60° ahead of (L4) or behind (L5) the planet. We report the detection of a Uranian Trojan; in our numerical integrations, 2011 QF 99 oscillates around the Uranian L4 Lagrange point for >70,000 years and remains co-orbital for ∼1 million years before becoming a Centaur. We constructed a Centaur model, supplied from the transneptunian region, to estimate temporary co-orbital capture frequency and duration (to a factor of 2 accuracy), finding that at any time 0.4 and 2.8% of the population will be Uranian and Neptunian co-orbitals, respectively. The co-orbital fraction (∼2.4%) among Centaurs in the International Astronomical Union Minor Planet Centre database is thus as expected under transneptunian supply.
Journal Article
Harmonizing tau positron emission tomography in Alzheimer's disease: The CenTauR scale and the joint propagation model
INTRODUCTION Tau‐positron emission tomography (PET) outcome data of patients with Alzheimer's disease (AD) cannot currently be meaningfully compared or combined when different tracers are used due to differences in tracer properties, instrumentation, and methods of analysis. METHODS Using head‐to‐head data from five cohorts with tau PET radiotracers designed to target tau deposition in AD, we tested a joint propagation model (JPM) to harmonize quantification (units termed “CenTauR” [CTR]). JPM is a statistical model that simultaneously models the relationships between head‐to‐head and anchor point data. JPM was compared to a linear regression approach analogous to the one used in the amyloid PET Centiloid scale. RESULTS A strong linear relationship was observed between CTR values across brain regions. Using the JPM approach, CTR estimates were similar to, but more accurate than, those derived using the linear regression approach. DISCUSSION Preliminary findings using the JPM support the development and adoption of a universal scale for tau‐PET quantification. Highlights Tested a novel joint propagation model (JPM) to harmonize quantification of tau PET. Units of common scale are termed “CenTauRs”. Tested a Centiloid‐like linear regression approach. Using five cohorts with head‐to‐head tau PET, JPM outperformed linearregressionbased approach. Strong linear relationship was observed between CenTauRs values across brain regions.
Journal Article
