Very high plasma densities can be obtained at the end of the implosion phase in inertial fusion targets, particularly in the so-called fast-ignition scheme (Tabak et al., 1994; Mulser & Bauer, 2004), where a central hot spark is not needed at all. By properly tailoring the fuel compression stage, degenerate states can be reached (Azechi et al., 1991; Nakai et al., 1991; McCory, 1998). In that case, most of the relevant energy transfer mechanisms involving electrons are affected (Honrubia & Tikhonchuk, 2004; Bibi & Matte, 2004; Bibi et al., 2004). For instance, bremsstrahlung emission is highly suppressed (Eliezer et al., 2003). In fact, a low ignition-temperature regime appears at very high plasma densities, due to radiation leakage reduction (León et al., 2001). Stopping power and ion-electron coulomb collisions are also changed in this case, which are important mechanisms to trigger ignition by the incoming fast jet, and to launch the fusion wave from the igniting region into the colder, degenerate plasma. All these points are reviewed in this paper. Although degenerate states would not be easy to obtain by target implosion, they present a very interesting upper limit that deserves more attention in order to complete the understanding on the different domains for inertial confinement fusion.

Recent advances in surgical techniques have made it possible to study the changes that are known as degeneration of the intervertebral disc (IVD) in greater depth than ever before. This is an important area of study because degeneration of the lumbar IVDs is associated, perhaps causally, with low back pain: one of the most common and debilitating conditions in the western world. The term degeneration implies an inevitable progression that is characteristic of wear-and-tear-associated conditions. However, modern research on human tissue has shown that this is not the case. Here, disruption of the micro-anatomy that is described as degeneration is an active process, which is probably regulated by locally produced cytokines. This one observation opens up the possibility of inhibiting or even reversing the processes of degeneration. The immediate question is how can the slowly progressive changes of degeneration be treated, particularly as connective tissue repair is thought to be a slow and highly regulated process. In this review, the possibility of using gene therapy as a single-shot, long-lasting therapeutic strategy is discussed, together with an outline of developments in this area to date.