A Maximum Stellar Surface Density in Dense Stellar Systems

We compile observations of the surface mass density profiles of dense stellar systems, including globular clusters in the Milky Way and nearby galaxies, massive star clusters in nearby starbursts, nuclear star clusters in dwarf spheroidals and late-type disks, ultra-compact dwarfs, and galaxy spheroids spanning the range from low-mass cusp bulges and ellipticals to massive core ellipticals. We show that in all cases the maximum stellar surface density attained in the central regions of these systems is similar, Sigma_max ~ 10^11 M_sun/kpc^2 (~20 g/cm^2), despite the fact that the systems span 7 orders of magnitude in total stellar mass M_star, 5 in effective radius R_e, and have a wide range in effective surface density M_star/R_e^2. The surface density limit is reached on a wide variety of physical scales in different systems and is thus not a limit on three-dimensional stellar density. Given the very different formation mechanisms involved in these different classes of objects, we argue that a single piece of physics likely determines Sigma_max. The radiation fields and winds produced by massive stars can have a significant influence on the formation of both star clusters and galaxies, while neither supernovae nor black hole accretion are important in star cluster formation. We thus conclude that feedback from massive stars likely accounts for the observed Sigma_max, plausibly because star formation reaches an Eddington-like flux that regulates the growth of these diverse systems. This suggests that current models of galaxy formation, which focus on feedback from supernovae and active galactic nuclei, are missing a crucial ingredient.Comment: 6 pages, 2 figures, accepted to MNRAS Letters (matches accepted version

Complications of Sulcus-supported Intraocular Lenses with Iris Sutures, Implanted during Penetrating Keratoplasty after Intracapsular Cataract Extraction

In a retrospective study, the authors analyzed visual results and postoperative complications in a series of 14 consecutive patients who had undergone penetrating keratoplasty and implantation of a posterior chamber intraocular lens (PC IOC) in the absence of the posterior capsule. Seven patients suffered from aphakic bullous keratopathy and seven from pseudophakic bullous keratopathy. Postoperative follow-up was 7.6 months on the average. Bestcorrected postoperative visual acuity was 20/60 or better in four cases and 20/200 or better in eight. Glaucoma was present before surgery in four eyes, which persisted in all cases and developed in four new cases. Results of gonioscopic examination showed the postoperative development of goniosynechiae in four eyes. Pseudophakodonesis of various extent was present in ten eyes. Preoperatively, cystoid macular edema was diagnosed angiographically in one case. It did not improve after surgery and was seen in three additional eyes postoperatively. Causes for postoperative visual acuity lower than 20/200 were cystoid macular edema in three cases, graft rejection in one case, central retinal scar in one case, and optic nerve atrophy in one case. A distortion of the pupil was seen in three eyes in miosis and in four additional eyes in mydriasis. Corneal thickness as well as anterior chamber depth were within normal limits. Fluorophotometric evaluation of the blood-aqueous barrier showed values comparable with those obtained after intracapsular cataract extraction and implantation of an iris-fixated IOL. Despite the relatively good visual results, the high postoperative incidence of cystoid macular edema and/or glaucoma may discourage the use of this technique. © 1990, American Academy of Ophthalmology, Inc. All rights reserved

Pathology Case Study: Progressive Hearing Loss

This is a case study presented by the University of Pittsburgh Department of Pathology in which a woman sought help for an progressive eight-year diminished sense of hearing, which developed with vertigo and left-side tinnitus. Visitors can view both microscopic and gross descriptions, including images, and have the opportunity to diagnose the patient. This is an excellent resource for students in the health sciences to familiarize themselves with using patient history and laboratory results to diagnose disease. It is also a helpful site for educators to introduce or test students of Neuropathology

Heroin-assisted treatment in Switzerland: a case study in policy change

BACKGROUND: Switzerland introduced a pragmatic national drug policy when the former conservative abstinence-orientated politics proved unable to cope with an escalating number of users and related negative consequences for public health and public order. The high visibility of 'needle parks' and the size of the acquired immune deficiency disorder (AIDS) epidemic called for a new approach and for national leadership. AIMS: To describe the intentions, the process and the results of setting up the new treatment approach of prescribing heroin to treatment resistant heroin addicts, as an example of drug policy change. MATERIALS AND METHODS: A systematic collection of relevant documents is analysed and used as evidence for describing the process of policy change. RESULTS: Measures to reduce the negative consequences of continued use and to prevent the spread of AIDS were started mainly by private initiatives and soon taken up officially in the 'four-pillar' drug policy (including harm reduction, prevention, treatment and law enforcement). Medical prescription of heroin to chronic, treatment-resistant heroin addicts was one of the innovations, based on extensive scientific and political preparation. Detailed documentation and evaluation, ample communication of results, adaptations made on the basis of results and extensive public debate helped to consolidate the new policy and heroin-assisted treatment, in spite of its limitations as an observational cohort study. All necessary steps were taken to proceed from a scientific experiment to a routine procedure. DISCUSSION: Comparable policy changes have been observed in a few other countries, such as The Netherlands and Germany, based on the Swiss experience, with equally positive results of heroin-assisted treatment. These experiments were designed as randomised controlled trials, comparing intravenous heroin against oral methadone, thereby demonstrating the specific value of pharmaceutical diamorphine for maintenance treatment in opiate dependence. The positive impact of policy change and the positive outcomes of heroin-assisted treatment were acknowledged increasingly nationally and internationally, but made it difficult to continue the process of adapting policy to new challenges, due to the low visibility of present drug problems and to changing political priorities. CONCLUSION: A major change in drug policy was effectively realised under typical conditions of a federalist country with a longstanding tradition of democratic consensus building. Facilitating factors were the size and visibility of the heroin problem, the rise of the Aids epidemic, and a pragmatic attitude of tolerating private initiatives opening the way to official policy change

Tractable flux-driven temperature, density, and rotation profile evolution with the quasilinear gyrokinetic transport model QuaLiKiz

Quasilinear turbulent transport models are a successful tool for prediction of core tokamak plasma profiles in many regimes. Their success hinges on the reproduction of local nonlinear gyrokinetic fluxes. We focus on significant progress in the quasilinear gyrokinetic transport model QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036), which employs an approximated solution of the mode structures to significantly speed up computation time compared to full linear gyrokinetic solvers. Optimisation of the dispersion relation solution algorithm within integrated modelling applications leads to flux calculations faster than local nonlinear simulations. This allows tractable simulation of flux-driven dynamic profile evolution including all transport channels: ion and electron heat, main particles, impurities, and momentum. Furthermore, QuaLiKiz now includes the impact of rotation and temperature anisotropy induced poloidal asymmetry on heavy impurity transport, important for W-transport applications. Application within the JETTO integrated modelling code results in 1 s of JET plasma simulation within 10 h using 10 CPUs. Simultaneous predictions of core density, temperature, and toroidal rotation profiles for both JET hybrid and baseline experiments are presented, covering both ion and electron turbulence scales. The simulations are successfully compared to measured profiles, with agreement mostly in the 5%-25% range according to standard figures of merit. QuaLiKiz is now open source and available at www.qualikiz.com