Drug treatment of intermittent claudication

Intermittent claudication is a major presenting manifestation of chronic obstructive peripheral arterial disease of the lower limbs. The goals of treatment in the absence of rest pain are relief of symptoms, improvement in walking distance and prevention of progression of disease. The effectiveness of drug therapy for intennittent claudication, however, remains controversial and despite numerous clinical trials, many experts are not convinced of their value. In this article the author describes the drugs most frequently uses and most extensively studied.peer-reviewe

On the measurement of comparative advantage

This article shows that the distribution of the standard measure of revealed comparative advantage (RCA), which runs from 0 to 8, has problematic properties. Due to its multiplicative specification, it has a moving mean without a useful interpretation, while its distribution depends on the number of countries and industries. This article proposes an alternative, additive RCA, running from –1 to +1, with a bell-shaped distribution that centres on a mean equal to zero, independent of the classifications used. Statistical tests show the additive index to be more stable empirically too. Furthermore, the article proposes an aggregate RCA that runs from 0, when pure intra-industry trade prevails, to 1 in the case of pure inter-industry trade. Comparable conclusions hold for the location quotient (LQ), which is used as a measure for the revealed locational attractiveness of certain regions or countries for certain types of industry.

An International Comparison of National Clusters

The presence of innovative clusters may positively influence domestic economic growth. If it is possible to identify these clusters, economic growth may be increased even further by developing policy that stimulates innovative clusters. Identifying clusters, however, is not an easy task. Input- output tables provide a possibility to identify clusters of sectors. These so-called meso clusters answer the question as to which sectors firms that work together stem from. Hence, meso-clusters provide a framework which indicates how a cluster may be composed. An earlier analysis identified Dutch meso clusters. This opens the possibility to compare these Dutch clusters with clusters in other countries, which helps to answer two questions. Firstly, it shows which clusters exist in which countries. These clusters highlight difference in the way sectors work together in different countries, which may explain different patterns of specialisation or even different economic growth rates. Secondly, differences between similar clusters in different countries are analysed. These differences may stem from, for example, different sectors in similar clusters or from different levels of innovation, productivity, profitability or different export positions of similar clusters. The present paper uses the cluster identification method to compare national clusters in ten countries: Australia, Canada, Denmark, France, Germany Italy, Japan, The Netherlands, The United Kingdom, and The United States. The most remarkable differences between clusters found in these countries and the most interesting differences between the sectors included in the same cluster in different countries are discussed. This provides insight in the differences of the inter-industry linkages in these countries.

The science of color and color vision

A survey of color science and color vision

On 'Nothing'

Nothing---the absence of spacetime---can be either an endpoint of tunneling, as in the bubble of nothing, or a starting point for tunneling, as in the quantum creation of a universe. We argue that these two tunnelings can be treated within a unified framework, and that, in both cases, nothing should be thought of as the limit of anti-de Sitter space in which the curvature length approaches zero. To study nothing, we study decays in models with perturbatively stabilized extra dimensions, which admit not just bubbles of nothing---topology-changing transitions in which the extra dimensions pinch off and a hole forms in spacetime---but also a whole family of topology-preserving transitions that nonetheless smoothly hollow out and approach the bubble of nothing in one limit. The bubble solutions that are close to this limit, bubbles of next-to- nothing, give us a controlled setting in which to understand nothing. Armed with this understanding, we are able to embed proposed mechanisms for the reverse process, tunneling from nothing to something, within the relatively secure foundation of the Coleman-De Luccia formalism and show that the Hawking-Turok instanton does not mediate the quantum creation of a universe.Comment: 26 pages, 12 figures, v2: minor updates, published as "On 'Nothing' as an infinitely negatively curved spacetime

Bubbles of Nothing and the Fastest Decay in the Landscape

The rate and manner of vacuum decay are calculated in an explicit flux compactification, including all thick-wall and gravitational effects. For landscapes built of many units of a single flux, the fastest decay is usually to discharge just one unit. By contrast, for landscapes built of a single unit each of many different fluxes, the fastest decay is usually to discharge all the flux at once, which destabilizes the radion and begets a bubble of nothing. By constructing the bubble of nothing as the limit in which ever more flux is removed, we gain new insight into the bubble's appearance. Finally, we describe a new instanton that mediates simultaneous flux tunneling and decompactification. Our model is the thin-brane approximation to six-dimensional Einstein-Maxwell theory.Comment: 18 pages, 8 figures; v2: minor change