Homoclinic bifurcations in radiating diffusion flames

We analyse the dynamics of a model describing a planar diffusion flame with radiative heat losses incorporating a single step kinetic using timestepping techniques for Lewis number equal to one. We construct the full bifurcation diagram with respect to the Damköhler number including the branches of oscillating solutions. Based on this analysis we found, for the first time, homoclinic bifurcations that mark the abrupt disappearance of the nonlinear oscillations near extinction as reported in experiments.     

Synthesis of 1-sulfonyl-2-arylpyrrolidines via intramolecular cyclization/Mannich-type reaction cascade of N-(4,4-diethoxybutyl)sulfonamides

Abstract

Herein, we report the successful application of a novel approach to 2-substituted pyrrolidines based on intramolecular cyclization/intermolecular Mannich-type cascade reaction of N-(4,4-diethoxybutyl)sulfonamides to the synthesis of pyrrolidines possessing heterocyclic and polyaromatic moieties. The proposed approach benefits from mild reaction conditions, moderate to high yields of target compounds and provides a convenient route to the previously unknown 1-sulfonyl-2-arylpyrrolidines.     

Evaluating the reliability of analytical results using a probability criterion: a Bayesian perspective

Methods validation is mandatory in order to assess the fitness of purpose of the developed analytical method. Of core importance at the end of the validation is the evaluation of the reliability of the individual results that will be generated during the routine application of the method. Regulatory guidelines provide a general framework to assess the validity of a method, but none address the issue of results reliability. In this study, a Bayesian approach is proposed to address this concern. Results reliability is defined here as "the probability (π) of an analytical method to provide analytical results (X) within predefined acceptance limits (±λ) around their reference or conventional true concentration values (μ(T)) over a defined concentration range and under given environmental and operating conditions." By providing the minimum reliability probability (π(min)) needed for the subsequent routine application of the method, as well as specifications or acceptance limits (±λ), the proposed Bayesian approach provides the effective probability of obtaining reliable future analytical results over the whole concentration range investigated. This is summarised in a single graph: the reliability profile. This Bayesian reliability profile is also compared to two frequentist approaches, the first one derived from the work of Dewé et al. [W. Dewé, B. Govaerts, B. Boulanger, E. Rozet, P. Chiap, Ph. Hubert, Chemometr. Intell. Lab. Syst. 85 (2007) 262-268] and the second proposed by Govaerts et al. [B. Govaerts, W. Dewé, M. Maumy, B. Boulanger, Qual. Reliab. Eng. Int. 24 (2008) 667-680]. Furthermore, to illustrate the applicability of the Bayesian reliability profile, this approach is also applied here to a bioanalytical method dedicated to the determination of ketoglutaric acid (KG) and hydroxymethylfurfural (HMF) in human plasma by SPE-HPLC-UV.     

Highly diastereoselective four-component synthesis of polysubstituted 2-piperidinones with three and four stereogenic centers

Research on Chemical Intermediates - A novel four-component diastereoselective synthesis of polysubstituted 2-piperidinones is reported. The Michael addition–Mannich cascade of...     

Quantum Algorithms in Hilbert Database

A fast quantum algorithm for a search and pattern recognition in a Hilbert space memory structure is proposed. All the memory information is mapped onto a unitary operator acting upon a quantum state which represents a piece of information to be retrieved. As a result of only one quantum measurement, the address of the required information encoded in a number of the corresponding row of the unitary matrix is determined. By combining direct and dot products, the dimensionality of the memory space can be made exponentially large, using only linear resources. However, since the preprocessing, i.e., mapping the memory information into a Hilbert space can appear to be exponentially expensive, the proposed algorithm will be effective for NASA applications when the preprocessing is implemented on the ground, while the memory search is performed on remote objects.     

A reducing-difference IR-spectral study of 4-aminopyridine

The IR-spectra of 4-aminopyridine (4-AP) in solution and in the solid state have been analyzed, using the reducing-difference procedure. Defining a more precise band assignment of a part of the characteristic frequencies of 4-AP, the data obtained proved in particular a Fermi-resonance splitting of the symmetric NH₂-stretch.     

Maximum travelling salesman problem

We present different types of techniques for designing algorithms with worst-case performances for the Maximum Travelling Salesman Problem. Supported by Byelarussian Fundamental Science Found and DAAD     

Astrocyte signaling in the presence of spatial inhomogeneities

Astrocytes, a special type of glial cells, were considered to have just a supporting role in information processing in the brain. However, several recent studies have shown that they can be chemically stimulated by various neurotransmitters, such as ATP, and can generate Ca2+ and ATP waves, which can propagate over many cell lengths before being blocked. Although pathological conditions, such as spreading depression and epilepsy, have been linked to abnormal wave propagation in astrocytic cellular networks, a quantitative understanding of the underlying characteristics is still lacking. Astrocytic cellular networks are inhomogeneous, in the sense that the domain they occupy contains passive regions or gaps, which are unable to support wave propagation. Thus, this work focuses on understanding the complex interplay between single-cell signal transduction, domain inhomogeneity, and the characteristics of wave propagation and blocking in astrocytic cellular networks. The single-cell signal transduction model that was employed accounts for ATP-mediated IP3 production, the subsequent Ca2+ release from the ER, and ATP release into the extracellular space. The model is excitable and thus an infinite range of wave propagation is observed if the domain of propagation is homogeneous. This is not always the case for inhomogeneous domains. To model wave propagation in inhomogeneous astrocytic networks, a reaction-diffusion framework was developed and one-gap as well as multiple-gap cases were simulated using an efficient finite-element algorithm. The minimum gap length that blocks the wave was computed as a function of excitability levels and geometric characteristics of the inhomogeneous network, such as the length of the active regions (cells). Complex transient patterns, such as wave reflection, wave trapping, and generation of echo waves, were also predicted by the model, and their relationship to the geometric characteristics of the network was evaluated. Therefore, the proposed model can help in the formulation of testable hypotheses to explain the observed abnormal wave propagation in pathological situations.     

Contact angles of protein black foam films under dynamic and equilibrium conditions

The contact angles of protein Newton black foam films from ALG (alpha-lactalbumin), BLG (beta-lactoglobulin) and BSA (bovine serum albumin) are measured here within. The measurements are carried out under dynamic and equilibrium conditions. For all proteins, a strong hystheresis effect of the contact angle is observed under dynamic conditions. An attempt is made to explain these results by the slow adsorption and desorption kinetics of the protein bilayers and by the dynamic structure and the rheology of the protein network forming the bubble walls. In addition, we propose a modification of the experimental device reported previously for contact angle measurements of large flat films in equilibrium. The advantages of this method are discussed in detail. Some shortcomings (precision, reproducibility) of this preliminary variant of the device in this initial stage of its application, do not allow one to draw reliable conclusions about the interactions of these films. Some improvements of the measurement quality are proposed.