Artificial motors

For highest versatility, operating under diverse conditions, artificial molecular motors should have the following properties, in the authors opinion. Artificial motors should be rotary, and operate unidirectionally. 

We have seen that biomotors driven by proton gradients or by ATP hydrolysis have evolved to perform many functions. Artificial motors designed to be driven by chemical reactions, photon absorption, or electron transfer have been created by Homo sapiens. The authors of this chapter have designed a photon-driven ratchet motor consisting of a dibenzofulvene rotor and a chiral, triaiylmethane stator. (Quantum yields for substituted dibenzofulvene rotors have been measured and are adequate for practical operation of the target motor. 

These problems can be dealt with by usiag artificial test cloths impregnated with various approximations of natural soils such as vacuum cleaner dust, dirt from air conditioner filters, clays, carbon black, fatty acids, dirty motor oil, and artificial sebum, either alone or ia combination (37,94—98). The soils are appHed by sprayiag, immersion, or padding. If the soils are carefully appHed, reproducible results can be obtained. Soil test cloths can be of great help ia detergency studies, when used with an understanding of their limitations. 

In the USA artificial graphite is now made on a scale exceeding 300 kilotonnes pa (1989), and is used mainly for electrodes, crucibles and vessels, and various unmachined shapes specialist uses include motor brushes and contacts and refractories of various sorts. 

The synchronization phenomenon is probably the best studied nonlinear phenomenon, and it has some engineering applications. Thus, for instance, an artificial synchronization can be easily produced and used for the very accurate control of the speed of small motors synchronized with quartz oscillators as the latter maintain their frequency very... 

We are able to construct mechanical arms that reproduce movements quite close to those performed by the human arm. The problem in implanting these arms is that movements have to be coordinated with all the other body movements under the brain s direction. There is one possibility for connecting the electronic systems of the artificial arm to the nervous signals (Fig. 33) coming from the brain in order to obtain coordinated movements separate those signals into different components and amplify every component to drive an artificial muscle or electric motor. 

Infants with classic phenylketonuria (PKU) are normal at birth but if untreated show slow development, severe mental retardation, autistic symptoms, and loss of motor control. Children may have pale skin and white-blonde hair. The neurotoxic effects relate to high levels of phenylalanine and not to the phenylketones from which the name of the disease derives. Infants are routinely screened a few days after birth for blood phenylalanine level. Treatment consists of a life-long semisynthetic diet restricted in phenylalanine (smalt quantities are necessary because it is an essential amino acid). Aspartame (N-aspartyl-phenylalanine methyl ester), which is widely used as an artificial sweetener, must be strictly avoided by phenyiketonurics. 

A number of researchers have tried training neural networks to achieve color constancy. A neural network basically consists of a set of nodes connected by weights (McClelland and Rumelhart 1986 Rumelhart and McClelland 1986 Zell 1994). Artificial neural networks are an abstraction from biological neural networks. Figure 8.2 shows a motor neuron in (a) and a network of eight artificial neurons on the right. A neuron may be in one of... 

Figure 8.2 A motor neuron (a) and small artificial neural network (b). A neuron collects signals from other neurons via its dendrites. If the neuron is sufficiently activated, it sends a signal to other neurons via its axon. Artificial neural network are often grouped into layers. Data is entered through the input layer. It is processed by the neurons of the hidden layer and then fed to the neurons of the output layer. (Illustration of motor neuron from Life ART Collection Images 1989-2001 by Lippincott Williams Wilkins used by permission from SmartDraw.com.)...

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