Compile time preparations for run time scheduling in monitors

High level programming language constructs are proposed for scheduling of concurrent operations on a shared variable. Proof rules are given that can be used to check if an adequate scheduling can be prepared from the program text. The basis for the constructs is the condition that must be fulfilled before an operation on a shared variable is performed (the precondition of the operation) and what can be proved to hold when an operation terminates (the postassertion of the operation).     

Local deformation in stretched polybutene-1 spherulites

The orientation of crystals in spherulites of modifications I and II of polybutene-1 was studied by micro-x-ray diffraction. Changes in such micro-x-ray diffraction patterns were measured in various regions of the spherulites as a function of strain and time. The relationship between micro-x-ray diffraction from parts of spherulites and macro-x-ray diffraction from entire spherulites is discussed. Changes are resolved into contributions arising from (1) deformation of spherulites with change in crystal orientation and (2) transformation of crystals from modification II to modification I.     

Correct measurement of birefringence in a nonuniform medium

The birefringence of an object is usually obtained from its retardation. For an object of variable refractive index and optic axis orientation, a matrix procedure should be used for relating the retardation to the birefringence. There are many cases in the literature where this correct procedure has not been used. The correct procedure is illustrated for the case of a polymer spherulite.     

Anisotropy of the dielectric relaxation of a crystalline polymer

A theory which relates the change in the strength of absorption to the change in crystal orientation function is presented for the anisotropy of dielectric relaxation for the dipolar orientation change in an oriented crystalline polymer. Experimental measurements are presented for the α dielectric absorption of a stretched ethylene–carbon monoxide copolymer and compared with the orientation of crystals of this copolymer as determined by x-ray diffraction.     

Optical detection of spin coherence in a defect center of a molecular crystal

Various optically detected spin coherence experiments have been performed at zero magnetic field in a tunable loop-gap cavity adapted for optical detection of magnetic resonance. Experiments on X-traps induced by guest molecules in chemically mixed p-dibromobenzene (DBB) crystals provide evidence that optically excited triplet states perform at 1.4 K fast jumps between magnetically well defined trap molecules. We conclude that the guest molecule p-dichlorobenzene is surrounded by at least 4 energetically distorted DBB host molecules.     

The facets of the polyhedral set determined by the Gale—Hoffman inequalities

The Gale—Hoffman inequalities characterize feasible external flow in a (capacitated) network. Among these inequalities, those that are redundant can be identified through a simple arc-connectedness criterion.This paper is dedicated to Phil Wolfe on the occasion of his 65th birthday.Research supported in part by NATO Collaborative Research Grant 0785/87.Supported in part by a grant of the Air Force Office of Scientific Research.     

Can extended objects explain the GSI e+ e− lines?

The anomalous electron-positron coincidences observed in heavy-ion collisions have been interpreted as signal for the pair decay of hitherto unknown neutral objects with masses around 1.8 MeV. We discuss the decay modes of such extended composite particles when they are bound to a nucleus. In particular we investigate the angular correlation of the emitted pair and the competing single-photon decay channel. We confront the particle hypothesis with recent negative results from experiments searching for resonances in Bhabha scattering. The induced pair decay of a metastable 1⁺⁺ state in secondary collisions with target atoms is discussed as a possible explanation.     

Characterization and properties of polyethylene blends I. Linear low-density polyethylene with high-density polyethylene

A blend system of linear low-density polyethylene (LLDPE) (ethylene butene-1 copolymer) with high-density (linear) polyethylene (HDPE) is investigated by differential scanning calorimetry (DSC), wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS), Raman longitudinal-acoustic-mode spectroscopy (LAM), and light scattering (LS). For slowly cooled or quenched samples, one single endotherm is evident in the DSC curve which depends on the composition. No separate peaks are observed in the WAXD, SAXS, Raman-LAM, and LS studies on the LLDPE/HDPE blends. This observation along with the fact that no peak broadening is observed suggests that these peaks are associated with the presence of a single component. In no case did we see double peaks or a broadened peak that might be associated with two closely spaced unresolved peaks. This suggests that segregation has not taken place at the structural levels of crystalline, lamellar, and spherulitic textures. A single-step drop in the scattered intensity (I_Hv) as a function of temperature is seen in the LS studies. It is therefore concluded that cocrystallization between the LLDPE and HDPE components occurs. The mechanical and optical α, β, and γ relaxations of these blends are explored by dynamic birefringence. The 50/50 blend displays the intermediate relaxation behavior between those of the components in all α, β, and γ regions. This observation is reminiscent of the characteristic of the typical miscible blends.     

Equilibrium Pure States and Nonequilibrium Chaos

We consider nonequilibrium systems such as the Edwards–Anderson Ising spin glass at a temperature where, in equilibrium, there are presumed to be (two or many) broken-symmetry pure states. Following a deep quench, we argue that as time t, although the system is usually in some pure state locally, either it never settles permanently on a fixed length scale into a single pure state, or it does, but then the pure state depends on both the initial spin configuration and the realization of the stochastic dynamics. But this latter case can occur only if there exists an uncountable number of pure states (for each coupling realization) with almost every pair having zero overlap. In both cases, almost no initial spin configuration is in the basin of attraction of a single pure state; that is, the configuration space (resulting from a deep quench) is all boundary (except for a set of measure zero). We prove that the former case holds for deeply quenched 2D ferromagnets. Our results raise the possibility that even if more than one pure state exists for an infinite system, time averages do not necessarily disagree with Boltzmann averages.