No abstract

This is a theoretical study of a situation where each residue of a linear biopolymer may adopt one of three conformational states. Such a situation exists in the case of DNA, since it may be in helical A, B, . . ., Z forms as well as the melted state. In the vicinity of the triple point in the phrase diagram three states, e.g. the A form, the B form and the denatured state, co-exist within a given molecule. We present an exact analytical solution of the simplest homopolymer model. Theory predicts that the presence of two helical states in one molecule should affect the helix-coil transition in two ways. The melting temperature experiences an upward shift and the melting range width is increased, by a factor of square root of two as a maximum.

Ensurance of the reliability of dams during their construction and operation is of exceptional importance. World hydraulic engineering practice has numerous examples when their unreliable operation not only caused substantial material losses but also led to human vic-Despite the fact that in recent years considerable progress has been made in dam construction, nonetheless present-day standards on the design of dams do not include problems of evaluating their reliability. The fact is that the effect of various factors on the safe operation of dams is not amenable to evaluation under laboratory conditions or theoretically owing to the individuality of each structure, different time of putting them into operation, and complexity of the designs and processes and phenomena occurring in the structures and also of the operation of these structures under various conditions and regimes.At present it is possible to evaluate the reliability of dams only on the basis of processing, analyzing, and generalizing statistlcal data on incidents and accidents occurring during operation of these structures.Despite the fact that data on incidents and accidents of dams have not been systematized yet, and sometimes are even contradictory (determination of the main factor causing dam accidents is complicated by differences in the conclusions of experts, as was the case, for example, with the Vajont, Malpasse, and other dams), the available information nevertheless permits establishing the effect of the main factors on the reliability of dams and evaluating their significance in the first approximation.Whereas until recently in the works of various authors the effect of the main factors (loss of stability of the foundation, intensified seepage in the structure, foundations, and bank abutments, shrinkage and temperature cracks, etc.) on the reliability of dams was evaluated only in percent, in works [4, 5] the dynamics of incidents and accidents on dams with time were established. This article generalizes the statistical treatment of about 700 cases of incidents and accidents on dams out of a total number of about 9000.On the basis of reliabillty theory [6] we established for various types of dams (gravity, arch, buttress, and earth) the probability density function of the time of accident-free, incident-free, and, as a whole, failure-free operation of these structures.% It was established as a result of the analysis that the distribution of the rates of incidents, accidents, and failures on dams with time, regardless of the type of the latter, is described sufficiently well by a two-parameter Welbull distribution.In this case the parameters of the distribution laws, reliability indices, and their confidence limits were established for accldent-free, incldent-free, and failure-free operation of various types of dams (Table 1).

This book is devoted to the 75th anniversary of the birth of Corresponding Member of the Academy of Sciences of the Georgian SSR and State Prize Winner, Professor M. A. Mostkov, a well-known specialist in the fields of hydropower, hydraulic engineering, and hydraulics. In this book the author describes the life and manysided activities of M. A. Mostkov (1900A. Mostkov ( -1956, who participated in the design of many hydroelectric plants and irrigation systems in Transcaucasia, and was Chief Project Engineer for the high-head Khram-I hydroelectric plant, for which he received a State Prize.