PubMed · 6757597
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M J Harper. Fertility control.. https://doi.org/10.1002/med.2610020406
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Excitable media, which range from autocatalytic chemical systems to biological cells and tissues, can maintain organized structures in the form of rotating spiral waves of excitation. The dynamics of spiral waves in two-dimensional systems have been shown to be susceptible to control by external fields (such as electric, thermal and optical). In three dimensions, the analogues of spiral waves are scroll waves. Here we show that an external field--a temperature gradient--can be used to control a particular class of scroll waves called scroll rings. The gradient allows scroll rings to be precisely oriented in space, and their spontaneous shrinkage to be accelerated, decelerated or even reversed (so that the ring expands). The temperature gradient also influences the lifetimes of the scroll rings. We suggest that these dynamics are likely to be generic to other types of field gradients and other excitable media.
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Eighteen low and medium resolution empirical energy functions were tested for their ability to distinguish correct from incorrect folds from three test sets of decoy protein conformations. The energy functions included 13 pairwise potentials of mean force, covering a wide range of functional forms and methods of parameterization, four potentials that attempt to detect properly formed hydrophobic cores, and one environment-based potential. the first of the three test sets consists of large ensembles of plausible conformations for eight small proteins, all of which have correct native secondary structure and are reasonably compact. The second is the set of all subconformations in a database of known protein structures applied to the sequences in that database (ungapped threading). The third is a set of ensembles of 1000 conformations each for seven small proteins taken from molecular dynamics simulations at 298 K and 498 K. Our results show that there are functions effective for each challenge set; moreover, success in one test is no guarantee of success in another. We examine the factors that seem to be important for accurate discrimination of correct structures in each of the test sets, and note that extremely simple functions are often as effective as more complex functions.