Indirect drive

Lindl, J. D. (1998). Inertial Confinement Fusion The Quest for Ignition and Energy Gain Using Indirect Drive. New York Sprmger-Verlag. 

Some cells couple the pure transport forms discussed on p. 218—i.e., passive transport (1) and active transport (2)—and use this mechanism to take up metabolites. In secondary active transport (3), which is used for example by epithelial cells in the small intestine and kidney to take up glucose and amino acids, there is a symport (S) located on the luminal side of the membrane, which takes up the metabolite M together with an Na" ion. An ATP-dependent Na transporter (Na /lC ATPase see p. 350) on the other side keeps the intracellular Na+ concentration low and thus indirectly drives the uptake of M. Finally, a uniport (U) releases M into the blood. 

The input shaft of the motor maybe either directly or indirectly connected to the speed reducer (Fig. 2.2). When it is hard-coupled directly through gears, the system is called direct drive. Indirect drive systems utilize belts and sheaves to connect the motor to the speed reducer. 

Each system has its advantages and disadvantages. Direct drive systems have better speed control and are more efficient,but maybe more expensive and time consumingto repair in the case of a system breakdown. Indirect drive systems allow more flexibility in motor location and are easier to repair if the problem simply requires a new belt. 

It is essential that during compression, the illumination of the target by the driver be extremely homogeneous and symmetrical. If the illumination by direct drive is not satisfactory, conversion of the direct radiation into a secondary radiation might be a solution indirect drive, see below). 

As mentioned earlier, a very homogeneous and symmetrical target illumination is one of the keys to success in inertial confinement research. This follows from the fact that the interface between the accelerated solid state and the ablating plasma is subject to Rayleigh-Taylor instability, as a heavy material is leaning on the more tenuous plasma. The instability grows exponentially from an initial perturbation caused by nonuniformities. Better than 1% uniform compression reduces the initial perturbation to such a level that, in the final stage, the pellet is still sufficiently compressed. The quest to reach uniform ablation has led to what is known as indirect drive (Lindl 1995). The distinction between this approach and the direct drive is as follows. 

The indirect drive target consists of both a fuel pellet and a small cylindrical cavity, inside which the pellet is located (see 60.2). 

Crucial aspects of the indirect drive are (inter alia)... 

The indirect drive target system, showing the fuei peiiet, the hohiraum and the driver beams with the resuiting X-rays... 

Even thongh direct drives appear to be more attractive, many extruders are made with indirect drives. An example of an extruder with an indirect drive is shown in Figure 20. 

Fig. 9.12. Muscle basic functions and antagonists, a Direct drive (dragonfly), b indirect drive (fly, bee)...

It has been pointed out that an intriguing feature of such ACNs is that agonis-tically related constituents amplify each other [43]. As a consequence, enhancement of the fittest, in response to a given effector, also induces promotion or survival of the unfittest (with respect to an effector or a set of conditions) It may well happen that the unfittest for a given effector E may present specific desirable properties, so that the effector E may be used to indirectly drive amplification of the unfittest and thus the generation of these properties. 

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