Risk-Neutral Pricing for Arbitrage Pricing Theory

Journal of Optimization Theory and Applications - We consider infinite-dimensional optimization problems motivated by the financial model called Arbitrage Pricing Theory. Using probabilistic and...     

Direct analysis in real time mass spectrometry (DART‐MS) of highly non‐polar low molecular weight polyisobutylenes

Low molecular weight polyisobutylenes (PIB) with chlorine, olefin and succinic acid end‐groups were studied using direct analysis in real time mass spectrometry (DART‐MS). To facilitate the adduct ion formation under DART conditions, NH₄Cl as an auxiliary reagent was deposited onto the PIB surface. It was found that chlorinated adduct ions of olefin and chlorine telechelic PIBs, i.e. [M + Cl]^? up to m/z 1100, and the deprotonated polyisobutylene succinic acid [M? H]^? were formed as observed in the negative ion mode. In the positive ion mode formation of [M + NH₄]⁺, adduct ions were detected. In the tandem mass (MS/MS) spectra of [M + Cl]^?, product ions were absent, suggesting a simple dissociation of the precursor [M + Cl]^? into a Cl^? ion and a neutral M without fragmentation of the PIB backbones. However, structurally important product ions were produced from the corresponding [M + NH₄]⁺ ions, allowing us to obtain valuable information on the arm‐length distributions of the PIBs containing aromatic initiator moiety. In addition, a model was developed to interpret the oligomer distributions and the number average molecular weights observed in DART‐MS for PIBs and other polymers of low molecular weight. Copyright © 2015 John Wiley & Sons, Ltd.     

Matrix-analytic solution of infinite,finite and level-dependent second-order fluid models

This paper presents a matrix-analytic solution for second-order Markov fluid models (also known as Markov-modulated Brownian motion) with level-dependent behavior. A set of thresholds is given that divide the fluid buffer into homogeneous regimes. The generator matrix of the background Markov chain, the fluid rates (drifts) and the variances can be regime dependent. The model allows the mixing of second-order states (with positive variance) and first-order states (with zero variance) and states with zero drift. The behavior at the upper and lower boundary can be reflecting, absorbing, or a combination of them. In every regime, the solution is expressed as a matrix-exponential combination, whose matrix parameters are given by the minimal nonnegative solution of matrix quadratic equations that can be obtained by any of the well-known solution methods available for quasi birth death processes. The probability masses and the initial vectors of the matrix-exponential terms are the solutions of a set of linear equations. However, to have the necessary number of equations, new relations are required for the level boundary behavior, relations that were not needed in first-order level dependent and in homogeneous (non-level-dependent) second-order fluid models. The method presented can solve systems with hundreds of states and hundreds of thresholds without numerical issues.     

Resolving the similarities and differences between the effect of structurally different actin-binding proteins on the thermodynamic properties of G-actin

Differential scanning calorimetry was applied to compare the effects of mammalian twinfilin-1 or toxofilin on the thermodynamic properties of actin monomer. Although twinfilin and toxofilin have different structure and actin-binding sites, they similarly increased the thermodynamic stability of monomeric actin. The mammalian twinfilin increased, while the toxofilin did not significantly change the T_1/2 value (the width at half-height of the transition peak) during the complex formation between the actin and the monomer binding proteins. In case of toxofilin, the E_A value (activation energy) significantly increased compared to twinfilin where the activation energy was nearly insensitive to the complex formation. It seems that toxofilin can achieve its main function as an actin monomer sequestering protein by more effectively and consistently modifying the basic thermodynamic properties of the monomeric actin.     

Estimation of Activation Energy from the Survival Yields: Fragmentation Study of Leucine Enkephalin and Polyethers by Tandem Mass Spectrometry

A simple collision model for multiple collisions occurring in quadrupole type mass spectrometers was derived and tested with leucine enkaphalin a common mass spectrometric standard with well-characterized properties. Implementation of the collision model and Rice-Ramsperger-Kassel-Marcus (RRKM) algorithm into a spreadsheet software allowed a good fitting of the calculated data to the experimental survival yield (SY) versus collision energy curve. In addition, fitting also ensured to estimate the efficiencies of the kinetic to internal energy conversion for Leucine enkephalin in quadrupole-time-of-flight and triple quadrupole instruments. It was observed that the experimental SY versus collision energy curves for the leucine enkephalin can be described by the Rice-Ramsperger-Kassel (RRK) formalism by reducing the total degrees of freedom (DOF) to about one-fifth. Furthermore, this collision model with the RRK formalism was used to estimate the critical energy (E _o ) of lithiated polyethers, including polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofurane (PTHF) with degrees of freedom similar to that of leucine enkephalin. Applying polyethers with similar DOF provided the elimination of the effect of DOF on the unimolecular reaction rate constant. The estimated value of E _o for PEG showed a relatively good agreement with the value calculated by high-level quantum chemical calculations reported in the literature. Interestingly, it was also found that the E _o values for the studied polyethers were similar.

Poly(vinyl alcohol)-based Amphiphilic Copolymer Aggregates as Drug Carrying Nanoparticles

A series of amphiphilic polyisobutylene-block-poly(vinyl alcohol) (PIB-b-PVA) copolymers of constant PIB and varying PVA block length was synthesized by living carbocationic polymerization and their solution behavior was studied. The synthesis involved the preparation of polyisobutylene-b-poly(tert.-butyl vinyl ether) followed by hydrolysis with hydrogen bromide. The copolymers were characterized by gel permeation chromatography, ¹H-NMR, and MALDI-TOF MS methods. The micellization behavior of the copolymers was investigated in aqueous media by direct dissolution and dialysis using static and dynamic light scattering. The critical micelle concentration, micelle size, aggregation number, and micelle shape were determined. The ability of the aggregates as drug carrying nanodevices was also investigated by doping them with indomethacin. UV-Vis measurements showed that the solubility of indomethacine increased significantly. Our findings suggest that the solubility is largely dependent upon the block segment ratios.     

Cinchona based squaramide catalysed enantioselective Michael addition of α-nitrophosphonates to aryl acrylates: enantioselective synthesis of quaternary α-aminophosphonates

Several cinchona based squaramide catalysts were applied to the asymmetric Michael addition of α-nitroethylphosphonates to acrylic acid aryl esters, resulting in high yields and enantioselectivities. The absolute configuration of one of the quaternary α-nitrophosphonate adducts was deduced from its experimental and calculated CD spectra. The adducts were reduced to their cyclic aminophosphonates by catalytic hydrogenation.