Ultrarelativistic black hole in an external electromagnetic field and gravitational waves in the Melvin universe

We investigate the ultrarelativistic boost of a Schwarzschild black hole immersed in an external electromagnetic field, described by an exact solution of the Einstein-Maxwell equations found by Ernst (the ``Schwarzschild-Melvin'' metric). Following the classical method of Aichelburg and Sexl, the gravitational field generated by a black hole moving ``with the speed of light'' and the transformed electromagnetic field are determined. The corresponding exact solution describes an impulsive gravitational wave propagating in the static, cylindrically symmetric, electrovac universe of Melvin, and for a vanishing electromagnetic field it reduces to the well known Aichelburg-Sexl pp-wave. In the boosting process, the original Petrov type I of the Schwarzschild-Melvin solution simplifies to the type II on the impulse, and to the type D elsewhere. The geometry of the wave front is studied, in particular its non-constant Gauss curvature. In addition, a more general class of impulsive waves in the Melvin universe is constructed by means of a six-dimensional embedding formalism adapted to the background. A coordinate system is also presented in which all the impulsive metrics take a continuous form. Finally, it is shown that these solutions are a limiting case of a family of exact gravitational waves with an arbitrary profile. This family is identified with a solution previously found by Garfinkle and Melvin. We thus complement their analysis, in particular demonstrating that such spacetimes are of type II and belong to the Kundt class.Comment: 11 pages, REVTeX

Doing Machismo: Legitimating speech acts as a selection discourse

This article explores the relationship between machismo and implicit power processes at a conceptual and empirical level. Implicit power processes are the taken-for-granted ways in which organizational members reproduce sexual divisions in their organizations. The empirical data are derived from the Argentine auto components industry. This is a male-dominated industry and machismo was used to explain and justify selection decisions that favoured men. Machismo is intrinsically linked to masculinity and power and should be defined as a set of hegemonic masculinities. Machismo represents four images of the dominant ideal of manhood in the Argentine society. These images are the authoritarian image, the breadwinner image, the virility image and the chivalry image. Machismo can then be studied as a discourse on masculinity that, when translated into particular selection discourses, implicitly leads to the exclusion of women from this industry. Machismo and implicit power processes are thus intertwined; both sexes routinely reproduce the male standard. In order to show how discourses on masculinity implicitly shape selection processes, this article presents a typology. The typology consists of four types, the power of natural differences, the power of denial, pastoral or caring power, and the power of the male standard. The typology serves as an analytical tool to reveal the intertwining of machismo and implicit power processes at the shop floors of Argentine auto components firms. © Blackwell Publishing Ltd 2005

Guidance for the assessment and management of prostate cancer treatment-induced bone loss. A consensus position statement from an expert group

Context and objective Incidence of prostate cancer (PC) is increasing, but androgen deprivation therapy (ADT) and other therapies are substantially improving survival. In this context, careful consideration of skeletal health is required to reduce the risk of treatment-related fragility fractures and their associated morbidity and mortality. This risk is currently not well-managed. ADT causes significant loss of bone mineral density (BMD). In the metastatic setting, systemic treatments (eg chemotherapy, abiraterone, enzalutamide) are used alongside ADT and may require concomitant glucocorticoids. Both ADT and glucocorticoids pose significant challenges to skeletal health in a population of patients already likely to have ongoing age-related bone loss and/or comorbid conditions. Current PC guidelines lack specific recommendations for optimising bone health. This guidance presents evidence for assessment and management of bone health in this population, with specific recommendations for clinical practitioners in day-to-day PC management. Methods Structured meetings of key opinion leaders were integrated with a systematic literature review. Input and endorsement was sought from patients, nursing representatives and specialist societies. Summary of guidance All men starting or continuing long-term ADT should receive lifestyle advice regarding bone health. Calcium/vitamin D supplementation should be offered if required. Fracture risk should be calculated (using the FRAX® tool), with BMD assessment included where feasible. BMD should always be assessed where fracture risk calculated using FRAX® alone is close to the intervention threshold. Intervention should be provided if indicated by local or national guidelines e.g. UK National Osteoporosis Guideline Group (NOGG) thresholds. Men requiring bone protection therapy should be further assessed (e.g. renal function), with referral to specialist centres if available and offered appropriate treatment to reduce fracture risk. Those near to, but below an intervention threshold, and patients going on to additional systemic therapies (particularly those requiring glucocorticoids), should have FRAX® (including BMD) repeated after 12-18 months. Patient Summary Modern treatments for prostate cancer have led to significant improvements in survival and quality of life. However, some of these treatments may lead to weakening of patient’s bones with risk of fracture and it is therefore important to monitor patients’ bone health and provide bone protection where needed. This paper provides specific guidance to clinical teams, based on the most recent research evidence, to ensure optimal bone health in their patients