Application of preparative gel-permeation chromatography to studies of low molecular weight carboxy-polybutadienes

Low molecular weight carboxy-polybutadiene liquid polymers are used as the binderfuel fraction in solid composite propellants. Analytical GPC determinations of low molecular weight materials (100 through 500 molecular weight range) were previously found to correlate significantly with final propellant properties. These low molecular weight materials are being characterized, and studies of their role in determining propellant physical properties are being conducted. Sufficient quantities of material in the 100–500 molecular weight range have been isolated by using preparative scale GPC to establish the chemical nature of these materials. Infrared and chemical analysis of fractions collected by using preparative GPC also has permitted the construction of functional group distribution profiles. In addition, narrow fractions isolated over the molecular weight range of the whole polymer were analyzed for average molecular weight by vapor pressure osmometry and have been used as calibration standards for analytical GPC.     

Adsorption at the liquid-vapor surface of a binary liquid mixture

In a binary liquid mixture, the component possessing the lowest surface tension preferentially adsorbs at the liquid-vapor surface. In the past this adsorption behavior has been extensively investigated for critical binary liquid mixtures near the mixture's critical temperature T(c). In this fluctuation-dominated regime the adsorption is described by a universal function of the dimensionless depth zxi where xi is the bulk correlation length. Fewer studies have quantitatively examined adsorption for off-critical mixtures because, in this case, one must carefully account for both the bulk and surface crossover from the fluctuation-dominated regime (close to T(c)) to the mean-field dominated regime (far from T(c)). In this paper we compare extensive liquid-vapor ellipsometric adsorption measurements for the mixture aniline+cyclohexane at a variety of critical and noncritical compositions with the crossover theory of Kiselev and co-workers [J. Chem. Phys. 112, 3370 (2000)].     

Multilevel sequential Monte Carlo: Mean square error bounds under verifiable conditions

In this article, we consider the multilevel sequential Monte Carlo (MLSMC) method of Beskos et al. (Stoch. Proc. Appl. [to appear]). This is a technique designed to approximate expectations w.r.t. probability laws associated to a discretization. For instance, in the context of inverse problems, where one discretizes the solution of a partial differential equation. The MLSMC approach is especially useful when independent, coupled sampling is not possible. Beskos et al. show that for MLSMC the computational effort to achieve a given error, can be less than independent sampling. In this article we significantly weaken the assumptions of Beskos et al., extending the proofs to non-compact state-spaces. The assumptions are based upon multiplicative drift conditions as in Kontoyiannis and Meyn (Electron. J. Probab. 10 [2005]: 61–123). The assumptions are verified for an example.     

Simulation and demonstration of electro-optic digital logic gates based on a single microring resonator

We propose and demonstrate directed optical digital logic function which can perform several logic gates using a single microring resonator. The mode operations achieved are logic buffer, inverter, AND, NAND, OR and NOR operations. Numerical simulations, in order to analyze its static as well as dynamic responses, are carried out. In addition, we also present the fundamental numerical principles used by the simulation software in order to fully justify the simulation results. These principles are divided into three components, structure based free carrier distribution principles, change in refractive index of the waveguide and the scattering analysis on the microring resonator coupling region.     

Synthesis of elliptical vanadoborates housing bimetallic centers [Zn4(B2O4H2)(V10B28O74H8)]8- and [Mn4(C2O4)(V10B28O74H8)]10-

The hydrothermal synthesis of three new vanadoborate compounds with elliptical (V10B28O74H8) clusters is described. The clusters contain pairs of bimetallic Zn2 or Mn2 units.