Hilbert Problems (Almost) 100 Years Later (From the Viewpoint of Interval Computations)

Reliable Computing -     

Effect of heparin on the lipid peroxidation reaction of erythrocytes and their stability

Physiological concentration (10 units/ml) of heparin activates ascorbate-dependent lipid peroxidation of erythrocytes and reduces their stability in the citrate-phosphate buffer (pH 3.0). In a concentration of 100 units/ml heparin does not influence the thermal (62 degrees) oxidation of methyloleate. It follows that heparin is not direct prooxidant.     

Hypothalamic neurons and defensive reflexes

Identified groups of neurons in positive (the lateral hypothalamic area, the lateral preoptic area) and negative (the ventromedial hypothalamus) emotional regions were examined under the different levels of food motivation and emotionally positive and negative intracranial stimulation. The responses of the neurons in classical and operant conditioning were different. This difference was manifested in tonic (during location of the animal into the chamber) and phasic alterations of neuronal activity and at certain stages of conditioned reflex performance. During classical conditioning were revealed the reciprocal relations in unit activity of the positive and negative emotional structures. During the operant reflex more complicated pattern of reactions was observed being connected with realization of a necessity of removing from the negative influences. During defensive reflex in the cases of classical conditioning and avoidance reaction reinforcement was related with engaging the negative emotional mechanisms while in the course of escape reaction the positive emotional mechanism being engaged.     

Vibratory embedment of long piles and tubes and their extraction

Conclusions 1. The vibration amplitude of a pipe being extracted or driven varies over its length.2. Loosening for various pipe sections occurs at different times.3. The possibility of extracting or embedding long elements without a significant increase in the induced and static forces is revealed in selecting a frequency regime with allowance for pipe elasticity.4. In cases where this is admissible under design and technological conditions, it is expedient to place the vibration exciter inside a large-diameter pipe (for example, at the base).The computational method proposed opens possibilities for the proven selection of parameters of the vibratory embedment or extraction of long elements. This method can be used especially effectively in developing vibratory-embedding apparatus with adjustable parameters. It enables us to determine preferable frequency zones and, on this basis, to develop an optimal algorithm for adjustment of the frequency regime.All-Union Scientific-Research Institute of Hydraulic and Sanitary Engineering. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 13–16, May–June 1984.     

The effect of random vaccine response on the vaccination coverage required to prevent epidemics

The response people have to vaccination varies because their immune systems differ and vaccine failures occur. Here we consider the effect that a random response, independent for each vaccinee, has on the vaccination coverage required to prevent epidemics in a large community. For a community of uniformly mixing individuals an explicit expression is found for the critical vaccination coverage (CVC) and the effect of the vaccine response is determined entirely by the mean E(AB), where A and B, respectively, reflect the infectivity and susceptibility of a vaccinated individual. This result shows that the usual concept of vaccine efficacy, which focuses on the amount of protection the vaccine provides the vaccinee against infection, is not adequate to describe the requirements for preventing epidemics when vaccination affect infectivity. The estimation of E(AB) poses a problem because A and B refer to the vaccine response of the same individual. Similar results are found when there are different types of individual, but now the mean E(AB) may differ between types. However, for a community made up of households it is shown that the CVC also depends on other characteristics of the vaccine response distribution. In practice this means that estimating a single measure of vaccine effectiveness is generally not enough to determine the CVC. For a specific community of households it is found that the vaccination coverage required to prevent epidemics decreases as the variation in the vaccine response increases.