Impact of Coffee Bean Roasting on the Content of Pyridines Determined by Analysis of Volatile Organic Compounds

The aim of the study was to analyze the process of roasting coffee beans in a convection–conduction roaster (CC) without a heat exchanger and a convection–conduction–radiation roaster (CCR) with a heat exchanger for determination of the aroma profile. The aroma profile was analyzed using the SPME/GC-MS technique, and an Agrinose electronic nose was used to determine the aroma profile intensity. Arabica coffee beans from five regions of the world, namely, Peru, Costa Rica, Ethiopia, Guatemala, and Brazil, were the research material. The chemometric analyses revealed the dominance of azines, alcohols, aldehydes, hydrazides, and acids in the coffee aroma profile. Their share distinguished the aroma profiles depending on the country of origin of the coffee beans. The high content of pyridine from the azine group was characteristic for the coffee roasting process in the convection–conduction roaster without a heat exchanger, which was shown by the PCA analysis. The increased content of pyridine resulted from the appearance of coal tar, especially in the CC roaster. Pyridine has an unpleasant and bitter plant-like odor, and its excess is detrimental to the human organism. The dominant and elevated content of pyridine is a defect of the coffee roasting process in the CC roaster compared to the process carried out in the CCR machine. The results obtained with the Agrinose showed that the CC roasting method had a significant effect on the sensor responses. The effect of coal tar on the coffee beans resulted in an undesirable aroma profile characterized by increased amounts of aromatic volatile compounds and higher responses of Agrinose sensors.     

Kinetics of the reaction of sodium arylthiolates with nitro-carboxybenzyl halide derivatives

The rate constants for the reactions of 4-halomethyl-3-nitrobenzoic acids, the nonnitro derivatives, and their ethyl esters with arylthiolates were measured at different temperatures. It was found that the retardation in rate constants compared to benzyl halides is due to the electrostatic repulsion between the electronegative substituents (COO⁻ and/or NO₂) in the substrates and thiolate ions. Good correlations between log k₂ values of the acids and carbon basicities of thiolates were found while log k₂ values of the esters show good straight lines with Hammett σ constants, pk_a, and carbon basicities of arylthiolates. © 1996 John Wiley & Sons Inc     

Lorenz’s attractor applied to the stream cipher (Ali-Pacha generator)

The safety of information is primarily founded today on the calculation of algorithms whose confidentiality depends on the number of the necessary bits for the definition of a cryptographic key. If this type of system has proved reliable, then the increasing power of the means of calculation threatens the confidentiality of these methods. The powerful computers are certainly able to quantify and decipher information quickly, but their computing speed allows parallel cryptanalysis, which aims “to break” a code by discovering the key, for example, by testing all the possible keys.

The only evocation of the principle of the quantum computer, with the potentially colossal capacities of calculation, has started a shock, even in the most savaged who are convinced of algorithmic cryptography. To mitigate this concern, we will introduce in this article a new cryptographic system based on chaotic concepts.     

Computation of surface roughness using optical correlation

The laser speckle photography is used to calculate the average surface roughness from the autocorrelation function of the aluminum diffuse objects. The computed results of surface roughness obtained from the profile shapes of the autocorrelation function of the diffuser show good agreement with the results obtained by the stylus profile meter.      

Determination of Some Metal Ions in Aquatic Environs by Atomic Absorption Spectrometry after Concentration with Modified Silica

The uptake behavior of porous silica modified with N‐propylsalicylaldimine (IE11) for Cd(II), Cr(III), Cu(II), Mn(II) and Pb(II) metal ions were studied. The Log k_d values were found to be within the range 2.19–5.16 depending on pH and time of stirring. IE11 was used in the separation and preconcentration of Cd(II), Cr(III), Cu(II), Mn(II) and Pb(II) from some natural water samples. The data were compared with those obtained by the solvent extraction method (APDC/MIBK). The method was found to be accurate and precise and not subject to random error.     

Regioselective bond cleavage in the dissociative electron transfer to benzyl thiocyanates

The electrochemical reduction of benzyl thiocyanate and p-nitrobenzyl thiocyanate was investigated in acetonitrile at an inert electrode. These two compounds reveal a change in the reductive cleavage mechanism, and more interestingly, they show a clear-cut example of a regioselective bond dissociation. Both phenomena may be understood on the basis of the dissociative ET theory and its extension to the formation/dissociation reactions of radical ions. While the effect of the standard oxidation potential of the leaving group seems to be predominant in understanding the change in the ET mechanism by changing the driving force, the regioselective cleavage is dictated by changes in the intrinsic barrier related to the nature of the substituent on the aryl moiety.     

Reactivity of 6-anisyl-5-cyano-4-oxo-2-thioxo-1,2,3,4-tetrahydro-pyrimidine to wards some electrophiles and nucleophiles

The title compound was subjected to react with some electrophiles and nucleophiles, such as alkyl halides, ethyl chloroacetate or amines, hydrazines etc. The resulting compounds were used in further syntheses for the purpose of obtaining some new types of heterocycles with possible biological and pharmaceutical activities.     

Parametric finite-volume micromechanics of periodic materials with elastoplastic phases

The recently incorporated parametric mapping capability into the finite-volume direct averaging micromechanics (FVDAM) theory has produced a paradigm shift in the theory’s development. The use of quadrilateral subvolumes made possible by the mapping facilitates efficient modeling of microstructures with arbitrarily shaped heterogeneities, and eliminates artificial stress concentrations produced by the rectangular subvolumes employed in the standard version. Herein, the parametric FVDAM theory is extended to the inelastic domain by implementing additional formulation required to accommodate plastic and thermal loading. Two different approaches of implementing plasticity have been investigated. The first approach is based on the treatment employed in previous versions of the theory wherein plastic strain fields are represented by a series expansion in Legendre polynomials. The second approach is based on direct surface-averaging of plastic strains calculated at a number of collocation points along the quadrilateral subvolumes’ surfaces, and offers substantial simplification in the parametric finite-volume theory’s elastic–plastic framework. Moreover, substantial reductions in execution times without loss of accuracy are realized due to the elimination of redundant plastic strain calculations in the subvolumes’ interiors employed in the evaluation of the Legendre polynomial coefficients. Numerical studies demonstrate the advantages of the parametric FVDAM theory relative to the standard version, together with new results that highlight its modeling capabilities vis-a-vis an emerging class of periodic lamellar materials with wavy microstructures and the thus-far undocumented architectural effects amplified by plasticity.     

A note on the minimum interval cost flow problem

We reduce the problem of minimum interval cost flow problem (MICFP) introduced by Hashemi et al. (2006) to the well-known minimum cost flow problem (MCFP).