Period adding bifurcation in a logistic map with memory

We introduce a single step memory dependence in the fully chaotic logistic map. This makes it a two dimensional system in general. However, we show that by using composite functions to define two one dimensional maps, it is possible to obtain some analytic results for the bifurcation structure. Numerical results support the calculated bifurcation scheme and, in addition, yield a further insight which allows the calculation of the convergence ratio for a new period adding scenario.     

Dehydration kinetics of an Indian clay

Decomposition of clay from Garo Hills of Meghalaya (India) was studied by dynamic thermogravimetry. A fourteen kinetic equation procedure was applied for analysis of non-isothermal weight change upto a temperature of 1223 K. Two stages of decomposition were clearly distinguised i.e. the initial dehydration period at temperature 373 K to 673 K and the dehydroxylation period in the temperature range 723 K to 1073 K. First order decomposition mechanism was found to be applicable to both dehydration and dehydroxylation steps. Activation energies of 67 kJ/mol and 278 kJ/mol are estimated for the first and second steps with frequency factors of 16.3 s^–1 and 5.16×10⁶s^–1 respectively. The weight loss relating to the steps in TG curves allows determination of the contents of the basic mineral in the clay. Percentages of Al₂O₃.SiO₂ and total volatiles as calculated from weight loss data are in accordance with the results of classical chemical analysis.

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Zusammenfassung Mittels DTG wurde die thermische Zersetung von Ton aus der Garo-Hills-Gegend bei Meghalaya (Indien) untersucht. Zur Analyse der nicht-isothermen Gewichtsveränderungen bis zu einer Temperatur von 1223 K wurde ein Verfahren mit vierzehn kinetischen Gleichungen angewendet. Zwei Teilschritte der Zersetzung können eindeutig unterschieden werden, nämlich die anfängliche Dehydratationsperiode bei Temperaturen von 373 bis 673 K und die Dehydroxylierungsperiode bei Temperaturen zwischen 723 K un 1073 K. Für beide Vorgänge konnte als Reaktionsmechanismus eine Zersetzung erster Ordnung angewendet werden. Für den ersten un zweiten Teilschritt konnten Aktivierungsenergien von 67 kJ/mol bzw. 278 kJ/mol un Frequenzfaktoren von 16.3s^–1 bzw. 5.16×10⁶s^–1 ermittelt werden. Der aus den TG-Kurven hervorgehende Gewichtsverlust läßt auf den Gehalt des Tones an Basismineral schließen. Der prozentuelle Gehalt an Al₂O₃, SiO₂ und der gesamten flüchtigen Bestandteile, berechnet aus den Gewichtsverlusdaten, stimmt mit den Ergebnissen aus herkömmlichen chemischen Analysen überein.

     

Structure and stability characteristics of turbulent planar flames with inhomogeneous jet in a concentric flow slot burner

Turbulent flames with compositionally inhomogeneous mixtures are common in many combustion systems. Turbulent jet flames with a circular nozzle burner were used earlier to study the impact of inhomogeneous mixtures, and these studies showed that the nozzle radius affects the flame stability. Accordingly, planar turbulent flames with inhomogeneous turbulent jet are created in a concentric flow slot burner (CFSB) to avoid this effect in the present study. The stability characteristics, the mixing field structure, and the flame front structure were measured, and the correlations between stability and the mixing field structure were investigated. The mixture fraction field was measured in non-reacting jets at the nozzle exit using highly resolved Rayleigh scattering technique, and the flame front was measured in some selected turbulent flames using high-speed Planar Laser-Induced Fluorescence (PLIF) of OH technique. The data show strong correlations between flame stability and the range of mixture fraction fluctuations. The flames are highly stabilized within a mixing field environment with the range of fluctuation in mixture fraction close to the range of the flammability limits. The mixing field structure is also illustrated and discussed using a mixing regime diagram and showed that the scatter of the data of the different cases is consistent with the classified mixing regimes. Lean flames are stabilized in the current slot burner. The flame front structure topology varies consistently from thin, small curvature at the low level of turbulence and higher equivalence ratio to more wrinkled, larger curvature, but a thicker structure at a higher level of turbulence and lower equivalence ratio.     

Synthesis of highly functionalized indeno[1,2-b]furans

Some novel functionalized indeno[1,2-b]furans were synthesized from the reaction of indandione/indanone and aldehydes at room temperature followed by the reaction of the Knoevenagel condendensed intermediate with 4-hydroxycoumarins in the presence of iodine as catalyst in dimethyl sulfoxide (DMSO) under thermal conditions. The reaction involved in a condensation and Michael addition followed by lactone ring opening and intramolecular cyclization process to afford the product in high yield in easy work-up procedure.     

CoFe2O4–SiO2–SO3H nanocomposite as a magnetically recoverable catalyst for oxidative bromination of alkynes

A hybrid catalyst has been prepared by incorporating sulfonic acid onto cobalt ferrite magnetic nanoparticles. The catalyst was successfully applied for rapid (20?min) synthesis of α,α-dibromoketones directly from alkynes and NBS. The reaction works well in the presence of 10?wt% of the catalyst at room temperature to produce the desired products in high yield. The catalyst could be recovered using an external magnet and reused without appreciable change in activity.     

Double-CO3(2-) centered [Co(II)5] wheel and modeling of its magnetic properties

A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin-orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2-300 K) yielding parameters of g and D (for the five-coordinate Co(II) ions), of A, κ, λ, and Δ (for the metals with spin-orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable.     

Copper(II) complexes of thioarylazo-pentanedione: Structures,magnetism, redox properties and correlation with DFT calculations

Copper(II) complexes of 3-((2-(alkylthio)phenylazo)-2,4-pentanedione, tridentate O, N, S donor ligands, are described in this work. Chloride bridged copper(II) polymers (1) and thiocyanato bridged copper(II) dimmers (2) are characterized by a single crystal X-ray diffraction study. The complexes show antiferromagnetic interactions, with J = −0.5 ± 0.1 cm⁻¹ (1a) and −25.8 ± 0.5 cm⁻¹ (2b), which implies stronger coupling in the –SCN-bridging compound. The spectra, redox and magnetism are explained by DFT studies.     

Amino Acid Based Low‐Molecular‐Weight Ionogels as Efficient Dye‐Adsorbing Agents and Templates for the Synthesis of TiO2 Nanoparticles

The gelation of ionic liquids is attracting significant attention because of its large spectrum of applications across different disciplines. These ‘green solvents’ have been the solution to a number of common problems due to their eco‐friendly features. To expand their applications, the gelation of ionic liquids has been achieved by using amino acid‐based low‐molecular‐weight compounds. Variation of individual segments in the molecular skeleton of the gelators, which comprise the amino acid and the protecting groups at the N and C termini, led to an understanding of the structure–property correlation of the ionogelation process. An aromatic ring containing amino acid‐based molecules protected with a phenyl or cyclohexyl group at the N terminus were efficient in the gelation of ionic liquids. In the case of aliphatic amino acids, gelation was more prominent with a phenyl group as the N‐terminal protecting agent. The probable factors responsible for this supramolecular association of the gelators in ionic liquids have been studied with the help of field‐emission SEM, ¹H NMR, FTIR, and luminescence studies. It is the hydrophilic–lipophilic balance that needs to be optimized for a molecule to induce gelation of the green solvents. Interestingly, to maximize the benefits from using these green solvents, these ionogels have been employed as templates for the synthesis of uniform‐sized TiO₂ nanoparticles (25–30 nm). Furthermore, as a complement to their applications, ionogels serve as efficient adsorbents of both cationic and anionic dyes and were distinctly better relative to their organogel counterparts.     

Single spin asymmetries in charged pion production from semi-inclusive deep inelastic scattering on a transversely polarized 3He Target at Q2 = 1.4-2.7 GeV2

We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations.     

Reverse self-assembly: (111)-oriented gold crystallization at alkylthiol monolayer templates

It has long been known that thiol-terminated molecules self-assemble as commensurate monolayers on Au(111) surfaces. By spreading floating octadecanethiol monolayers on aqueous solutions of chloroauric acid (HAuCl4) and using x rays to reduce the gold ions as well as to probe the structure, we have observed the nucleation of (111)-oriented Au nanoparticles at thiol surfaces. This process may be similar to the formation of biogenic gold by bacteria. The thiol monolayer acts as a "soft template," changing its structure as Au crystals form so that there is a sqrt[3]×sqrt[3] commensurate relationship.