Minimizing the number of transitions with respect to observation equivalence

Labeled transition systems (lts) provide an operational semantics for many specification languages. In order to abstract unrelevant details of lts's, manybehavioural equivalences have been defined; here observation equivalence is considered. We are interested in the following problem:Given a finite lts, which is the minimal observation equivalent lts corresponding to it? It is well known that the number of states of an lts can be minimized by applying arelational coarsest partition algorithm. However, the obtained lts is not unique (up to the renaming of the states): for an lts there may exist several observation equivalent lts's which have the minimal number of states but varying number of transitions. In this paper we show how the number of transitions can be minimized, obtaining a unique lts.     

On the Frequency of Zeros of Solutions of Second Order Linear Differential Equations

We consider the equation \(\rm f^{\prime\prime}+{A}(z){f}=0\) with linearly independent solutions f₁,₂, where A(z) is a transcendental entire function of finite order. Conditions are given on A(z) which ensure that max{λ(f₁),λ(f₂)} = ∞, where λ(g) denotes the exponent of convergence of the zeros of g. We show as a special case of a further result that if P(z) is a non-constant, real, even polynomial with positive leading coefficient then every non-trivial solution of \(\rm f^{\prime\prime}+{e}^P{f}=0\) satisfies λ(f) = ∞. Finally we consider the particular equation \(\rm f^{\prime\prime}+({e}^Z-K){f}=0\) where K is a constant, which is of interest in that, depending on K, either every solution has λ(f) = ∞ or there exist two independent solutions f₁, f₂ each with λ(f_i) ≤ 1.     

Particle-stabilized emulsions comprised of solid droplets

We kinetically stabilize oil-in-water emulsions comprising paraffin crystals by adsorbing solid particles (silica) of colloidal size at the oil/water interface. We obtain a set of emulsions that are quiescently stable for a long period of time (months), while the same emulsions are destabilized after only a few hours in the presence of surfactant molecules alone. The emulsions are submitted to a shear stress in order to probe their stability under flow conditions. Partial coalescence and gelation occur when the shear is applied for a sufficiently long period of time. The experiments reveal the existence of a critical droplet mass fraction, phi*, that defines a sharp transition between slow and fast gelation. The process of gelation is rather slow for phi < phi*, occurring at the scale of hours, and becomes almost instantaneous above phi*.     

Isolation and Characterization of Cellulosic Pulp Fines and Their Interactions with Cationic Polyacrylamides

Four different types of cellulosic fines were isolated from refiner mechanical and kraft pulp samples to characterize their chemical and physical properties. The pulp fines were flocculated using four different types of cationically modified polyacrylamides. The extent of flocculation was observed with multiple light scattering apparatus. The maximum adsorption of the polyelectrolytes on the pulp fines was determined by polyelectrolyte titration. It was concluded that it is the combination of the molar mass and the charge density of a polyelectrolyte, as well as the origins and characteristics of the fines which define the adsorption and flocculation behavior. None of these properties alone could fully describe these phenomena, but the molar mass of the polyelectrolyte was the predominant factor. The most important fines characteristics were the charge properties and the microstructure.     

Asymmetric cellulose nanocrystals: thiolation of reducing end groups via NHS–EDC coupling

Cellulose nanocrystals (CNC) were functionalized in aqueous media at the reducing, aldehyde ends of cellulose. CNC oxidation to produce carboxyl groups was followed by carbodiimide-mediated reaction to install thiol groups. The selectivity and extent of thiolation at the reducing ends was qualitatively confirmed by imaging (transmission electron microscopy) silver nanoparticles that tagged the CNC termini and by X-ray photoelectron spectroscopy, respectively. The adsorption of thiolated CNC onto gold surfaces as well as the viscoelastic property of the formed adlayer was investigated by using quartz crystal microgravimetry. The thiolated CNC chemisorbed on the surfaces were further analyzed for surface density and distribution by using atomic force microscopy. Overall we introduce a facile, mild asymmetric thiolation procedure as an efficient alternative to conventional reductive amination.     

Conjugation of linoleic acid over a hydrogen pre-activated heterogeneous catalyst

Development of a new heterogeneous catalytic pathway for isomerization of linoleic acid to conjugated linoleic acids at mild reaction conditions over Ni/H-MCM-41 in a soluted system.     

Resumming Long-Distance Contributions to the QCD Pressure

The strict coupling constant expansion for the free energy of hot QCD plasma shows bad convergence at all reasonable temperatures, and does not agree well with its 4D lattice determination. This has recently led to various refined resummations, whereby the agreement with the lattice result should improve, at the cost of a loss of a formal agreement with the coupling constant expansion and particularly with its large infrared sensitive "long-distance" contributions. We show here how to resum the dominant long-distance effects by using a 3D effective field theory, and determine their magnitude by simple lattice Monte Carlo simulations.