Structure changes in glassforming liquids upon cooling and compression

Upon cooling and compression, both the thermodynamic and the kinetic properties of glassformers change. In fragile glassformers, these changes suggest changes in the local structure of the liquid. Thermodynamic data may then provide a measure of structure changes. Special criteria for structure changes in terms of energy and pressure fluctuations in the isochoric system are proposed; recent theoretical results allow one to rewrite the criteria in terms of long- and short-time thermodynamic characteristics of the liquid. Based on the proposed criteria, we discuss the changes in the local structure due to temperature and pressure variations.     

Nonadiabatic alignment of asymmetric top molecules: field-free alignment of iodobenzene

Nonadiabatic laser alignment of an asymmetric top molecule is studied using the combination of a quantum dynamical theory and time-resolved photofragment imaging experiments. In particular, the degree of alignment of iodobenzene, induced by an intense, linearly polarized picosecond laser pulse, is calculated and measured. Pronounced alignment is obtained under field-free conditions.     

Capillary force on a nanoscale tip in dip-pen nanolithography

Monte Carlo simulation has been used to characterize the capillary force due to the condensation of a liquid meniscus between a tip with a nanoscale asperity and a flat surface. To consider both hydrophobic and hydrophilic molecules coating the tip as a model of dip-pen nanolithography, tips with various wettabilities are studied. The capillary force due to the meniscus is calculated for various saturations (humidities). We have implemented a thermodynamic integration technique that can project the force into energetic and entropic contributions. In most cases, the force is mainly energetic in origin. At the snap-off separation where the meniscus disappears, the tip feels a significant entropic force at high saturation. Our calculation shows nonmonotonic behavior of the pull-off force as a function of saturation, which is in qualitative accord with experiments.     

Markov partitions for anosov flows onn-dimensional manifolds

In this work we construct a Markov partition for transitive Anosov flows, such that the measure of the boundary of the partition is zero. Symbolic dynamics for these flows is also developed.     

Multicycle fatigue resistance of brittle polymers

Conclusion A model of multicycle fatigue of polymers based on the hypothesis of self-simulation of the failure process was proposed and a method of predicting the durability was elaborated in the present study. It was found that in low-temperature conditions of self-heating, the crack is the basic cause of fatigue failure. A cyclic durability equation was obtained in the form of a modified time summation criterion for the stressed state in the failure zone in the vicinity of the apex of a fatigue crack. It was shown that in the case of brittle failure in multicycle fatigue, the maximum principal stresses which arise in the failure zone, one order of magnitude smaller than the size of the fatigue crack, are the criterion of failure.Translated from Mekhanika Kompozitnykh Materialov, No. 4, pp. 633–638, July–August, 1990.     

Thermoactivation theory of wear in plastics

It has been shown that wear, being a thermofluctuation process, can be described by an equation analogous to Zhurkov's law of simple fracture. In fatigue wear the maximum value of the activation energy u₀ is close to the u for the rupture of chemical bonds. Abrasive wear is an almost barrierless process, therefore in the case of mixed wear the presence of an abrasive component sharply reduced u₀. The thermoactivation equation describes the effect of temperature on wear only within the limits of one physical state of the polymer. In transition zones it is necessary to take into account the role of the sharp change in elongation at break, which introduces extrema into the temperature wear curve.Mekhanika Polimerov, Vol. 2, No. 6, pp. 867–874, 1966     

LIGHT-DRIVEN MOVEMENTS IN THE SOLAR TRACKING LEAF OF Lupinus palaestinus Boiss. (Fabaceae)

Abstract— The palmatcly-compound leaf lamina of Lupinus palaestinus Boiss. tracks the sun by independent diaphototropic movements of its individual leaflets, operated by the appropriate flexing of their pulvinules. The lamina also exhibits two additional, light-dependent nastic movements, that can operate concurrently with the diaphototropic response: (1) a nyctinastic response to light/dark transitions bv which all the leaflets fold down simultaneously and at equal rates, and which is reversed by a photonastic response to dark/light transitions by which all the leaflets unfold into a co-planar configuration; (2) a photonastic upward folding ("cupping"), which all the leaflets exhibit simultaneously and at equal rates in response to high irradiance. thereby modulating their diaphototropic response to reduce light interception and evade over-exposure. Although the individual leaflets can sense all these tight-signals and respond to them independently, they do so simultaneously, so that the entire lamina responds in a co-ordinated manner, as a unit. The photoreceptors for the two nastic responses are localized in the individual pulvinules and may or may not be the same. The photoreceptors for the diaphototropic perception are localized in the proximal segment of the lamina of the individual leaflets, adjacent to but outside the pulvinule. The separation of the sites of perception for the tropic and nastic responses allows these responses to operate concurrently. The capacity of the diaphototropic response to occur concurrently with one or the other of the two nastic responses may be accounted for by its inductive nature.