An Appraisal of Developments in Surgical and Catheter-based Cardiovascular Therapy

After a few decades of limited experience in treating congenital heart defects, the introduction of cardiopulmonary bypass in 1954 provided the opportunity to advance cardiac surgery into an adult patient population. In the 1960s this resulted in the first aortic and mitral valve procedures to treat patients with valvular stenosis and/or regurgitation. Evolving from ball-caged valves to stentless porcine bioprosthetic valves, tens of millions of patients have undergone aortic, mitral, or combined valve replacements with excellent short- and long-term valve durability and survival, even with the earliest generation of mechanical valves. Ischemic heart disease was the leading cause of death in the general population (Figure 1), and the only treatment available at that time -- medical therapy -- fell short to reduce early mortality. Despite the pioneering work of Arthur M. Vineberg to induce coronary anastomosis of an internal mammary artery graft by burrowing it in the myocardium, surgical revascularization did not take off until in the mid-1960s when coronary artery bypass grafting (CABG) through surgical anastomosis was introduced. Its wide-spread adoption caused CABG to rapidly evolve as the standard of care for patients suffering from coronary artery disease

Optimized Verlet-like algorithms for molecular dynamics simulations

New explicit velocity- and position-Verlet-like algorithms of the second order are proposed to integrate the equations of motion in many-body systems. The algorithms are derived on the basis of an extended decomposition scheme at the presence of a free parameter. The nonzero value for this parameter is obtained by reducing the influence of truncated terms to a minimum. As a result, the new algorithms appear to be more efficient than the original Verlet versions which correspond to a particular case when the introduced parameter is equal to zero. Like the original versions, the proposed counterparts are symplectic and time reversible, but lead to an improved accuracy in the generated solutions at the same overall computational costs. The advantages of the new algorithms are demonstrated in molecular dynamics simulations of a Lennard-Jones fluid.Comment: 5 pages, 2 figures; submitted to Phys. Rev.

Effectiveness of the global protected area network in representing species diversity

The Fifth World Parks Congress in Durban, South Africa, announced in September 2003 that the global network of protected areas now covers 11.5% of the planet's land surface. This surpasses the 10% target proposed a decade earlier, at the Caracas Congress, for 9 out of 14 major terrestrial biomes. Such uniform targets based on percentage of area have become deeply embedded into national and international conservation planning. Although politically expedient, the scientific basis and conservation value of these targets have been questioned. In practice, however, little is known of how to set appropriate targets, or of the extent to which the current global protected area network fulfils its goal of protecting biodiversity. Here, we combine five global data sets on the distribution of species and protected areas to provide the first global gap analysis assessing the effectiveness of protected areas in representing species diversity. We show that the global network is far from complete, and demonstrate the inadequacy of uniform—that is, 'one size fits all'—conservation targets