Gamma-rays from millisecond pulsars in Globular Clusters

Globular clusters (GCs) with their ages of the order of several billion years contain many final products of evolution of stars such as: neutron stars, white dwarfs and probably also black holes. These compact objects can be at present responsible for the acceleration of particles to relativistic energies. Therefore, gamma-ray emission is expected from GCs as a result of radiation processes occurring either in the inner magnetosperes of millisecond pulsars or in the vicinity of accreting neutron stars and white dwarfs or as a result of interaction of particles leaving the compact objects with the strong radiation field within the GC. Recently, GeV gamma-ray emission has been detected from several GCs by the new satellite observatory Fermi. Also Cherenkov telescopes reported interesting upper limits at the TeV energies which start to constrain the content of GCs. We review the results of these gamma-ray observations in the context of recent scenarios for their origin.Comment: 20 pages, 9 figures, will be published in Astrophysics and Space Science Series (Springer), eds. N. Rea and D.F. Torre

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

Gamma-Ray Pulsars

Gamma-ray photons from young pulsars allow the deepest insight into the properties and interactions of high-energy particles with magnetic and photon fields in a pulsar magnetosphere. Measurements with the Compton Gamma-Ray Observatory have led to the detection of nearly ten gamma-ray pulsars. Although quite a variety of individual signatures is found for these pulsars, some general characteristics can be summarized: (1) the gamma-ray lightcurves of most high-energy pulsars show two major peaks with the pulsed emission covering more than 50% of the rotation, i.e. a wide beam of emission; (2) the gamma-ray spectra of pulsars are hard (power law index less than 2), often with a luminosity maximum around 1 GeV. A spectral cutoff above several GeV is found; (3) the spectra vary with rotational phase indicating different sites of emission; and (4) the gamma-luminosity scales with the particle flux from the open regions of the magnetosphere (Goldreich-Julian current).Comment: 9 pages, 9 figures, 2 tables. To appear in the Proceedings of the 270. WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, Jan. 21-25, 2002, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J. Truemper. Proceedings are available as MPE-Report 27

Marjolin's ulcers at a university teaching hospital in Northwestern Tanzania: a retrospective review of 56 cases

Marjolin's ulcer is a rare but highly aggressive squamous cell cancer that is most often associated with chronic burn wounds. Although many individual case reports exist, no comprehensive evaluation of Marjolin's ulcer patients has been conducted in our setting. This study was conducted to describe the clinicopathological presentation and treatment outcome of this condition in our local setting and to identify predictors of outcome. This was a retrospective study of histologically confirmed cases of Marjolin's ulcer seen at Bugando Medical Centre over a period of 10-years between January 2001 and December 2010. Data were retrieved from patients' files and analyzed using SPSS computer software version 15.0 A total of 56 patients were studied. Male to female ratio was 2.1:1. Burn scars (89.3%) were the most common causative lesions of Marjolin's ulcer. The mean latent period between original injury and diagnosis of Marjolin's ulcer was 11.34 ± 6.14 years. Only 12.0% of the reported cases were grafted at the time of injury (P < 0.00). Most patients (48.2%) presented between one and five years of onset of illness. The lower limb (42.9%) was the most frequent site for Marjolin's ulcers. The median tumor size at presentation was 8 cm and the vast majority of patients (85.7%) presented with large tumors of ≥ 5 cm in diameter. Lymph node metastasis at the time of diagnosis was recorded in 32.1% of cases and distant metastasis accounted for 26.9% of cases. Squamous cell carcinoma (91.1%) was the most common histopathological type. Wide local excision was the most common surgical procedure performed in 80.8% of cases. Post-operative complication rate was 32.1% of which surgical site infection was the most common complication in 38.9% of patients. Local recurrence was noted in 33.3% of cases who were treated surgically. The mean length of hospital stay for in-patients was 7.9 ± 2.3 days. Mortality rate was 7.1%. According to multivariate logistic regression analysis, stage and grade of the tumor and presence of local recurrence were the main predictors of death (P < 0.001). Marjolin's ulcers are not rare in our environment and commonly occur in burn scars that were not skin grafted and were left to heal secondarily. A high index of suspicion is required in the management of chronic non-healing ulcers and all suspected lesions should be biopsed. Early recognition and aggressive treatment of Marjolin's ulcers and close follow-up are urgently needed to improve outcomes in our environment

Exploring models for the length of stay distribution.

Diagnosis Related Groups (DRG) are frequently used to standardize the comparison of consumption variables, such as length of stay (LOS). In order to be reliable, this comparison must control for the presence of outliers, i.e. values far removed from the pattern set by the majority of the data. Indeed, outliers can distort the usual statistical summaries, such as means and variances. A common practice is to trim LOS values according to various empirical rules, but there is little theoretical support for choosing between alternative procedures. This pilot study explores the possibility of describing LOS distributions with parametric models which provide the necessary framework for the use of robust methods