Gravitational Wave Polarization Modes in f(R)f(R) Theories

Many studies have been carried out in the literature to evaluate the number of polarization modes of gravitational waves in modified theories, in particular in $f(R)$ theories. In the latter ones, besides the usual two transverse-traceless tensor modes present in general relativity, there are two additional scalar ones: a massive longitudinal mode and a massless transverse mode (the so-called breathing mode). This last mode has often been overlooked in the literature, due to the assumption that the application of the Lorenz gauge implies transverse-traceless wave solutions. We however show that this is in general not possible and, in particular, that the traceless condition cannot be imposed due to the fact that we no longer have a Minkowski background metric. Our findings are in agreement with the results found using the Newman-Penrose formalism, and thus clarify the inconsistencies found so far in the literature.Comment: 7 pages; accepted for publication in Phys. Rev.

A comparative political economy of regional migration and labour mobility in West and Southern Africa

Based on a collaboration with the late Lionel Cliffe, this article suggests agendas and methods for analysing regional patterns of migration and labour mobility in Southern and West Africa. It locates local communities in regional patterns and global processes using two key organising concepts: first, the regionalisation of Africa, as outlined in Samir Amin's work. We consider continuities and discontinuities with the paradigms of ‘Africa of the labour reserves’ and ‘Africa of the colonial trade economy’ to understand contemporary realities. Second, this article explores the mechanisms and characteristics of cheap labour on different scales of analysis. This includes a discussion of the theories that explored the relations of reproduction of labour, and the reproduction of the labour system as a whole. In doing so, it rethinks the modes of production discourse to highlight the continuing importance of situations where capitalism exists alongside non-capitalist relations of production and reproduction

The Family-Company-Compact

"This paper deals with the relationship between the Hudson's Bay Company and the early administration of Vancouver Island.

Lifestyle for cardiovascular prevention. How relevant to the health needs of South Africa?

The concept that the ideal lifestyle changes will improve heath and longevity may only be feasible for the fortunate few who have time, knowledge and energy to devote to this important health issue. I have called the critical five lifestyle factors the “Big Five” to help in spreading the concept.(1) Such mnemonics sound good and we all know of the health benefits but, as the saying goes, “the spirit is willing but the flesh is weak.” What is practical? How do the lifestyle Big Five fit in with the better known Risk Factor concept and the increasing number of guidelines

An Unauthorized Admiralty Court in British Columbia

"The first Court of Vice-Admiralty to be set up in British Columbia was in existence for nine months before it was aware that the authority under which it was instituted and held pleas was illegal. Its story is part of the history of Vancouver's Island and illustrates once more how the resourceful Douglas was equal to a situation when it arose even if the remedy was extra-constitutional.

The five-point heart healthy lifestyle

The “Lifestyle Big-Five” are, in order of importance, nonsmoking, daily exercise for 30 min or more, a body mass index of 25 or less, the ideal diet  and last and least, modest alcohol. This lifestyle is associated with a pattern of maximal freedom from cardiovascular disease, stroke and with improved longevity. The major data supporting the “Lifestyle Big-Five” chiefly come from the results of the Nurses’ Health Study over 26 years and the Health Professionals Study over 20 years, both in the USA. Both these studies are supported by several large European studies including one that by computer randomly recruited a selected population. Apart from the evidence for non-smoking, which is already well-established and well-known, each of the other four components are evaluated in this review, with recommendations for application to patients. SAHeart 2011; 8:154-16

Digitalis reappraised: Still here today, but gone tomorrow?

Digoxin is one of the oldest of drugs acting on the heart and still one of the most frequently used. While in atrial fibrillation digoxin continues to have a valid role in the control of ventricular rate when added to beta-blockers and calcium antagonists, digoxin for heart failure is no longer a supportable option in view of the negative recent meta-analysis

An Unauthorized Admiralty Court in British Columbia

"The first Court of Vice-Admiralty to be set up in British Columbia was in existence for nine months before it was aware that the authority under which it was instituted and held pleas was illegal. Its story is part of the history of Vancouver's Island and illustrates once more how the resourceful Douglas was equal to a situation when it arose even if the remedy was extra-constitutional.