Dynamical evolution of star forming regions - II. Basic kinematics

We follow the dynamical evolution of young star-forming regions with a wide range of initial conditions and examine how the radial velocity dispersion, $\sigma$, evolves over time. We compare this velocity dispersion to the theoretically expected value for the velocity dispersion if a region were in virial equilibrium, $\sigma_{\rm vir}$ and thus assess the virial state ($\sigma / \sigma_{\rm vir}$) of these systems. We find that in regions that are initially subvirial, or in global virial equilibrium but subvirial on local scales, the system relaxes to virial equilibrium within several million years, or roughly 25 - 50 crossing times, according to the measured virial ratio. However, the measured velocity dispersion, $\sigma$, appears to be a bad diagnostic of the current virial state of these systems as it suggests that they become supervirial when compared to the velocity dispersion estimated from the virial mass, $\sigma_{\rm vir}$. We suggest that this discrepancy is caused by the fact that the regions are never fully relaxed, and that the early non-equilibrium evolution is imprinted in the one-dimensional velocity dispersion at these early epochs. If measured early enough ($<$2 Myr in our simulations, or $\sim$20 crossing times), the velocity dispersion can be used to determine whether a region was highly supervirial at birth without the risk of degeneracy. We show that combining $\sigma$, or the ratio of $\sigma$ to the interquartile range (IQR) dispersion, with measures of spatial structure, places stronger constraints on the dynamical history of a region than using the velocity dispersion in isolation.Comment: 20 pages, 14 figures, accepted for publication in MNRA

Bound states of Van der Waals trimers

A method for calculating the energy levels and wave functions of floppy tri- atomic systems such as rare-gas trimers has been developed. It is based upon a potential-optimized discrete variable representation and takes into account the wide-amplitude vibrations that occur in such systems. The quadrature error that occurs in DVR calculations is analysed and a method of correction implemented. The diagonalisation procedure is based upon a combination of successive diagonalisation and truncation and a Lanczos diagonaliser. Using this method the wave functions of the Ar(_3) Van der Waals trimer have been calculated. The wave functions for the low-lying states show very regular behaviour. Above the barrier to linearity, most of the wave functions are irregular but some have simple nodal patterns that suggest localization along periodic orbits. In addition to the "horseshoe" states previously described for H(^+)(_3), localized features corresponding to symmetric and antisym metric stretching vibrations around a linear configuration have been identified. The different localized modes can be combined to form more complex states in a manner analogous to normal modes. A preliminary study of the rotational states of Ar(_3) has also been performed. The rotational constants for the low lying states of Ar(_3) reflect the increasing average size of Ar(_3) with increasing vibrational excitation. The rotational constants are obtained from two methods, expectation values and energy level differences. The results for the levels above the barrier to isomerisation reveal that the simple models used for obtaining the rotational constants are no longer valid and indicate that a more sophisticated treatment is necessary

Ureteropelvic junction obstruction caused by metastatic cholangiocarcinoma

We describe the rare case of a 61-year-old female with right ureteropelvic junction (UPJ) obstruction caused by metastatic cholangiocarcinoma. Her past medical history was notable for cholangiocarcinoma treated with neoadjuvant chemoradiation and two orthotopic liver transplants six years earlier. Urology was consulted when she presented with flank pain and urinary tract infection. Diagnostic workup demonstrated right UPJ obstruction. She was managed acutely with percutaneous nephrostomy. She subsequently underwent robotic pyeloplasty and intrinsic obstruction of the UPJ was discovered. Histological examination revealed adenocarcinoma, consistent with systemic recurrence of the patient\u27s known cholangiocarcinoma

The Stellar Activity - Rotation Relationship

Using a new catalog of 824 solar and late-type stars with X-ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity. From an unbiased subset of this sample the power law slope of the unsaturated regime, $L_X/L_{bol}\propto Ro^\beta$, is fit as $\beta=-2.70\pm0.13$. This is inconsistent with the canonical $\beta=-2$ slope to a confidence of 5$\sigma$ and argues for an interface-type dynamo. Super-saturation is observed for the fastest rotators in our sample and its parametric dependencies are explored. Significant correlations are found with both the corotation radius and the excess polar updraft, the latter theory being supported by other observations. We also present a new X-ray population synthesis model of the mature stellar component of our Galaxy and use it to reproduce deep observations of a high Galactic latitude field. The model, XStar, can be used to test models of stellar spin-down and dynamo decay, as well as for estimating stellar X-ray contamination rates for non-stellar studies.Comment: 4 pages, 4 figures. To appear in the proceedings of Cool Stars 17: 17th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, AN 334, 1-2, Eds Klaus Strassmeier and Mercedes Lopez-Morale

How COVID has Illuminated the Pitfalls of a Single-Payer System in the US

Health care quality measures are impacted by resources invested into outcomes. COVID-19 has had a direct impact upon quality outcomes, the same illuminating just some of the problems with the concept of a single-payer health care system. The US government\u27s inefficiencies in attempting to run the single-payer system known as IHS in context with its repeated failures in managing the COVID-19 crises along with the economic impact of the same, is but one call for strong leadership to dispel the myth that a single-payer system is a panacea for America

Randomized Polypill Crossover Trial in People Aged 50 and Over

PMCID: PMC3399742This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited