A new 4D chaotic system with hidden attractor and its engineering applications: Analog circuit design and field programmable gate array implementation

Nowadays, designing chaotic systems with hidden attractor is one of the most interesting topics in nonlinear dynamics and chaos. In this paper, a new 4D chaotic system is proposed. This new chaotic system has no equilibria, and so it belongs to the category of systems with hidden attractors. Dynamical features of this system are investigated with the help of its state-space portraits, bifurcation diagram, Lyapunov exponents diagram, and basin of attraction. Also a hardware realisation of this system is proposed by using field programmable gate arrays (FPGA). In addition, an electronic circuit design for the chaotic system is introduced.     

Modified jerk system with self-exciting and hidden flows and the effect of time delays on existence of multi-stability

In this paper, we report a new chaotic jerk system which shows self-excited and hidden oscillations depending on its parameters. Dynamic analysis shows that the proposed system exhibits multi-stability and coexisting attractors. To study the effect of time delays on the multi-stability feature of the system, we introduce multiple time delays in the third state variable. Investigation of dynamical properties of the time-delayed system shows the disappearance of multi-stability. Such a feature has not been reported earlier in the literatures.     

Structures of Eight Thio(semi)carbazones Derived from 2-Acetylpyrazine, 2-Acetythiazole and Acetophenone

Abstract  The structures of eight related thio(semi)carbazones are described. These are syn,1E-2-acetylpyrazine-3-thiosemicarbazone (1), syn,1E,4Z-2-acetylpyrazine-4-ethyl-3-thiosemicarbazone, (2) and syn,1Z-2-acetylpyrazine-4,4-dimethyl-3-thiosemicarbazone (3), syn,1E,4Z-2-acetylthiazole-4-phenyl-3-thiosemicarbazone (4), syn,1Z-phenyl-4,4-dimethyl-3-thiosemicarbazone (5), syn,1E,4Z-phenyl-4-methyl-3-thiosemicarbazone (6), syn,1E,4Z-phenyl-4-ethyl-3-thiosemicarbazone (7), syn,1E,4Z-2-acetophenone-5-(N-aminothionyl)-3-thiocarbazone (8). Crystal data: for 1: triclinic, P-1, a = 5.4053(10) ?, b = 7.435(3) ?, c = 11.772(4) ?, α = 81.70(3)°, β = 82.59(2)°, γ = 77.38(2)°, and Z = 2: for 2: triclinic, P-1, a = 7.322(3) ?, b = 7.8239(16) ?, c = 9.783(4) ?, α = 87.73(2)°, β = 79.46(3)°, γ = 80.41(2)°, and Z = 2; for 3: orthorhombic, Pnma, a = 13.5210(15) ?, b = 6.6914(5) ?, c = 11.7214(10) ?, and Z = 4; for 4: triclinic, P-1, a = 5.7058(7) ?, b = 9.8776(15) ?, c = 11.869(2) ?, α = 76.389(12)°, β = 86.364(13)°, γ = 88.322(12)°, and Z = 2; for 5: triclinic, P-1, a = 7.5362(3) ?, b = 8.6331(4) ?, c = 9.8753(4) ?, α = 91.401(4)°, β = 102.532(4)°, γ = 110.540(4)°, and Z = 2; for 6: monoclinic, P2(1)/c, a = 10.7178(4) ?, b = 5.5866(2) ?, c = 18.7647(9) ?, β = 104.392(5)°, and Z = 4; for 7: monoclinic, P2(1)/c, a = 8.9557(3) ?, b = 9.7418(4) ?, c = 13.6864(5) ?, β = 94.044(4)°, and Z = 4; for 8: triclinic, P-1, a = 9.8091(5) ?, b = 10.6173(4) ?, c = 16.4691(7) ?, α = 75.540(4)°, β = 80.305(4)°, γ = 65.192(4)°, and Z = 4. Structures 1, 2, 4, 5, 7, and 8 form intramolecular N4–H···N1 hydrogen-bonds. Structures 3 and 5 exist in the tautomeric form in which N1 is protonated. Graphical Abstract  Structures of thio(semi)carbazones were found to fall into two categories: those with intramolecular N4-H…N1 hydrogen-bonds, and those which show a tautomeric form in which N1 is protonated.      

In Silico Target Identification of Galangin,as an Herbal Flavonoid against Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a heterogenous group of malignancies in the bile duct, which proliferates aggressively. CCA is highly prevalent in Northeastern Thailand wherein it is associated with liver fluke infection, or Opisthorchis viverrini (OV). Most patients are diagnosed in advanced stages, when the cancer has metastasized or severely progressed, thereby limiting treatment options. Several studies investigate the effect of traditional Thai medicinal plants that may be potential therapeutic options in combating CCA. Galangin is one such herbal flavonoid that has medicinal properties and exhibits anti-tumor properties in various cancers. In this study, we investigate the role of Galangin in inhibiting cell proliferation, invasion, and migration in OV-infected CCA cell lines. We discovered that Galangin reduced cell viability and colony formation by inducing apoptosis in CCA cell lines in a dose-dependent manner. Further, Galangin also effectively inhibited invasion and migration in OV-infected CCA cells by reduction of MMP2 and MMP9 enzymatic activity. Additionally, using proteomics, we identified proteins affected post-treatment with Galangin. Enrichment analysis revealed that several kinase pathways were affected by Galangin, and the signature corroborated with that of small molecule kinase inhibitors. Hence, we identified putative targets of Galangin using an in silico approach which highlighted c-Met as candidate target. Galangin effectively inhibited c-Met phosphorylation and subsequent signaling in in vitro CCA cells. In addition, Galangin was able to inhibit HGF, a mediator of c-Met signaling, by suppressing HGF-stimulated invasion, as well as migration and MMP9 activity. This shows that Galangin can be a useful anti-metastatic therapeutic strategy in a subtype of CCA patients.     

Self-assembled monolayers on electrode surfaces: a probe for redox kinetics

The formation and characterization of self-assembled monolayers of organosulfur compounds like alkanethiols and dialkyl (di)sulfides on metal surfaces such as gold are areas of current research interest. The presence of an aromatic ring in a thiol molecule can enhance the binding between Au and the thiol, resulting in the formation of compact and impervious self-assembled monolayers. The formation of a monolayer of 2-mercaptobenzothiazole (MBT), containing an aromatic group with a fused thiazole ring but no long alkyl chain, is achieved on a gold electrode surface. Voltammetric investigations of ferro/ferricyanide and ferrous/ferric redox systems carried out on this Au|MBT electrode are reported. Further, the possibility of using such an Au|MBT electrode to distinguish between inner and outer sphere electron transfer reactions is indicated. Received: 2 January 1998 / Accepted: 14 May 1998     

Samarium-induced reductive dimerization of methyl cinnamate: synthesis of 2,8-diamino chrysene

Samarium metal-induced reductive dimerization of methyl cinnamate was performed for the first time. A unique role for aluminum was indicated in the dimerization reaction. The intermediate adipate ester was converted to 2,8-diamino chrysene.     

Correlation analysis of reactivity in the reduction of trans-chloro(RC6H4NH2)bis(1,2-diaminoethane)cobalt(III) complexes by hexacyanoferrate(II) in aqueous methanol

The structural and solvent effects on the reduction of trans-chloro(RC₆H₄NH₂)bis(1,2-diaminoethane)cobalt(III) ion (R=H, p-Me, p-OMe, p-OEt, p-F, m-Me and m-OMe) by the hexacyanoferrate(II) complex was investigated in aqueous MeOH. The second order rate constants for these reactions were determined spectrophotometrically at three different temperatures and activation parameters have been computed. Reduction proceeding through ion-pair formation is proposed on the basis of the Laidler–Eyring and Grunwald–Winstein equations. The influence of added co-solvent on the reactivity has been analysed using multiple regression equations viz. Kamlet–Taft and Swain. The reduction rates were correlated with Hammett's substituent constants yielding a negative reaction constant.     

Solvent and chelation effects on the photoreduction of cobalt(III)–amine complexes in aqueous–organic solvent media

The photoreduction of trans-[Co(NH₃)₄Cl₂]⁺, trans-[Co(en)₂Cl₂]⁺, [Co(dien)Cl₃], [Co(trien)Cl₂]⁺, and [Co(tetren)Cl]²⁺, ions has been studied using a low pressure Hg vapour lamp as light source (254 nm) in aqueous–organic solvents [0–30% (v/v) MeOH or 1,4-dioxane]. Quantum yields for Co^II production by redox decomposition have been determined in all the cases, and increase considerably with the increase in concentration of MeOH or 1,4-dioxane in the binary solvent mixtures under investigation. A plot of log(quantum yield) versus the Grunwald–Winstein Parameter, Y, which is a measure of solvent ionizing power, shows that a different blend of general and specific solvent interacts with the solute. This kind of specific solvent interaction on the reactant/excited state has been analysed using multiple regression: viz. Krygowski–Fawcett and Kamlet–Taft equations. Reasons for the difference in reactivity with chelation are also discussed.     

Formal total synthesis of camptothecin via ring-closing metathesis strategy

A formal total synthesis of camptothecin 1 is presented. The key steps include construction of the D-ring of camptothecin featuring an efficient ring-closing metathesis (RCM) reaction and the subsequent Michael addition of nitropropane across the double bond of the dihydropyridone 3.