Noise-intensity fluctuation in Langevin model and its higher-order Fokker-Planck equation

In this paper, we investigate a Langevin model subjected to stochastic intensity noise (SIN), which incorporates temporal fluctuations in noise-intensity. We derive a higher-order Fokker-Planck equation (HFPE) of the system, taking into account the effect of SIN by the adiabatic elimination technique. Stationary distributions of the HFPE are calculated by using the perturbation expansion. We investigate the effect of SIN in three cases: (a) parabolic and quartic bistable potentials with additive noise, (b) a quartic potential with multiplicative noise, and (c) a stochastic gene expression model. We find that the existence of noise-intensity fluctuations induces an intriguing phenomenon of a bimodal-to-trimodal transition in probability distributions. These results are validated with Monte Carlo simulations.     

Edgeworth expansion for the kernel quantile estimator

Using the kernel estimator of the pth quantile of a distribution brings about an improvement in comparison to the sample quantile estimator. The size and order of this improvement is revealed when studying the Edgeworth expansion of the kernel estimator. Using one more term beyond the normal approximation significantly improves the accuracy for small to moderate samples. The investigation is non- standard since the influence function of the resulting L-statistic explicitly depends on the sample size. We obtain the expansion, justify its validity and demonstrate the numerical gains in using it.     

Simultaneous determination of serine enantiomers in plasma using Mosher's reagent and stable isotope dilution gas chromatography-mass spectrometry

D-Serine is a co-agonist of the N-methyl-D-aspartate receptor in glutamate neurotransmission and has been proposed as a potential therapeutic agent for schizophrenia. However, D-serine also acts as a nephrotoxic substance in rats at high doses. To investigate the pharmacokinetics and toxicokinetics of D-serine, a method for the stereoselective determination of serine enantiomers in rat plasma was developed using GC-MS with selected ion monitoring (GC-MS-SIM). DL-[(2)H(3)]Serine was used as an internal standard to account for losses associated with the extraction, derivatization and chromatography. Serine enantiomers were purified by cation-exchange chromatography using BondElut SCX cartridge and derivatized with HCl in methanol to form methyl ester followed by subsequent N,O-diacylation with optically active (+)-α-methoxy-α-trifluoromethylphenylacetyl chloride to form epimeric amide. Quantitation was performed by SIM of the molecular-related ions of the epimers in the chemical ionization mode. The intra- and inter-day reproducibility of the assay was less than 5% for D-serine and 3% for L-serine. The method was successively applied to study the pharmacokinetics of D-serine in rats.     

Stereoselective Aldol Reaction of α-Phenylseleno Esters

Abstract

The TiCl₄-catalyzed reaction of a-phenylseleno esters with aldehydes in the presence of Ph₃P or Ph₃P=O gives aldol products with high syn selectivity.     

Silafunctional Compounds in Organic Synthesis. XXXVII. Metalated (Allyl) Aminosilanes: Regioselective Coupling with Alkyl Halides to (E)-1-Alkenylsilanes with a Functional Group on Silicon

(E)-1-Alkenylsilanes with an amino or an alkoxy group on silicon can be conveniently synthesized by regioselective coupling of a potassium reagent derived from an allyl(amino)silane with alkyl halides.     

Oxidative Coupling of Carbon Acid Compounds by Means of Ag2O

Transition-metal catalyzed coupling of carbanions by means of transition metal compounds has constituted a convenient method of the carbon-carbon bond formation in organic synthesis.¹ Recently, CuCl₂-promoted coupling of lithium enolates of ketones² and esters³ has been reported, which provides new routes to 1,4-diketones and succinate derivatives, respectively. Now we found that some carbon acids, such as acylacetate and monosubstituted malonate, were readily oxidatively dimerized by Ag₂O without intervention of their carbanions in dimethyl sulfoxide (DMSO) according to eq. 1.     

Successful preferential formation of a novel macromolecular assembly--trilayered polymeric micelle--that can incorporate hydrophilic compounds: the optimization of factors affecting the micelle formation from amphiphilic block copolymers

We have developed a novel macromolecular assembly, trilayered polymeric micelle, which can incorporate hydrophilic compounds. The micelle can be prepared from the amphiphilic block copolymers without regard to their properties such as the copolymer's charges and the homogeneity of the copolymers forming the micelle's inner and outer parts. In this study, we investigated the optimal condition for the preferential formation of the trilayered polymeric micelle. GPC results clarified that the composition of the block copolymer, the concentration of PVA in the aqueous bulk phase, and the temperature during the preparation were the important preparation factors affecting preferential formation of the trilayered polymeric micelles. We successfully achieved the preferential formation of the trilayered polymeric micelles under optimal conditions. Furthermore, we confirmed that the model hydrophilic compound, FITC-dextran, was successfully encapsulated into the hydrophilic core of the trilayered polymeric micelles. The novel micelle that can incorporate hydrophilic compounds can have a variety of future medical applications such as a protein delivery-based therapy.     

Radial transport characteristics of fast ions due to energetic-particle modes inside the last closed-flux surface in the compact helical system

The internal behavior of fast ions interacting with magnetohydrodynamic bursts excited by energetic ions has been experimentally investigated in the compact helical system. The resonant convective oscillation of fast ions was identified inside the last closed-flux surface during an energetic-particle mode (EPM) burst. The phase difference between the fast-ion oscillation and the EPM, indicating the coupling strength between them, remains a certain value during the EPM burst and drives an anomalous transport of fast ions.     

Anti-Markovnikov Addition of Anilines to Aliphatic Terminal Alkynes Catalyzed by an 8-Quinolinolato Rhodium Complex

Anti-Markovnikov addition of anilines to aliphatic terminal alkynes proceeded using an 8-quinolinolato rhodium/phosphine catalyst system. The use of a strong organic base, 1,1,3,3,–tetramethylguanidine, in the catalyst system enabled the formation of the aldimine products. Substrates with various functional groups including polar groups such as a phenolic hydroxy group are applicable to the hydroamination.