Spacecraft formation flying in the port-Hamiltonian framework

The problem of controlling the relative position and velocity in multi-spacecraft formation flying in the planetary orbits is an enabling technology for current and future research. This paper proposes a family of tracking controllers for different dynamics of Spacecraft Formation Flying (SFF) in the framework of port-Hamiltonian (pH) systems through application of timed Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). The leader–multi-follower architecture is used to address this problem. In this regard, first we model the spacecraft motion in the pH framework in the Earth Centered Inertial frame and then transform it to the Hill frame which is a special local coordinate system. By this technique, we may present a unified structure which encompasses linear/nonlinear dynamics, with/without perturbation. Then, using the timed IDA-PBC method and the contraction analysis, a new method for controlling a family of SFF dynamics is developed. The numerical simulations show the efficiency of the approach in two different cases of missions.

     

Novel tacrine-based acetylcholinesterase inhibitors as potential agents for the treatment of Alzheimer’s disease: Quinolotacrine hybrids

A new series of quinolotacrine hybrids including cyclopenta- and cyclohexa-quinolotacrine derivatives were designed, synthesized, and assessed as anti-cholinesterase (ChE) agents. The designed derivatives indicated higher inhibitory effect on the acetylcholinesterase (AChE) with IC₅₀ values of 0.285–100 µM compared to butyrylcholinesterase (BChE) with IC₅₀ values of?>?100 µM. Of these compounds, cyclohexa-quinolotacrine hybrids displayed a little better anti-AChE activity than cyclopenta-quinolotacrine hybrids. Compound 8-amino-7-(3-hydroxyphenyl)-5,7,9,10,11,12-hexahydro-6H-pyrano[2,3-b:5,6-c'] diquinolin-6-one (6m) including 3-hydroxyphenyl and cyclohexane ring moieties exhibited the best AChE inhibitory activity with IC₅₀ value of 0.285 µM. The kinetic and molecular docking studies indicated that compound 6m occupied both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE as a mixed inhibitor. Using neuroprotective assay against H₂O₂-induced cell death in PC12 cells, the compound 6h illustrated significant protection among the assessed compounds. In silico ADME studies estimated good drug-likeness for the designed compounds. As a result, these quinolotacrine hybrids can be very encouraging AChE inhibitors to treat Alzheimer’s disease.

Graphic abstract

A novel series of quinolotacrine hybrids were designed, synthesized, and evaluated against AChE and BChE enzymes as potential agents for the treatment of AD. The hybrids showed good to significant inhibitory activity against AChE (0.285–100 μM) compared to butyrylcholinesterase (BChE) with IC₅₀ values of?>?100 μM. Among them, compound 8-amino-7-(3-hydroxyphenyl)-5,7,9,10,11,12-hexahydro-6H-pyrano[2,3-b:5,6-c′] diquinolin-6-one (6 m) bearing 3-hydroxyphenyl moiety and cyclohexane ring exhibited the highest anti-AChE activity with IC₅₀ value of 0.285 μM. The kinetic and molecular docking studies illustrated that compound 6 m is a mixed inhibitor and binds to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE.

     

Kinetic determination of silver ion by its perturbation on Belousov-Zhabotinskii oscillating chemical reaction using potentiometric method.

Silver ion can perturb the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction. Therefore, the B-Z oscillating system was applied in the determination of silver ion by using a platinum wire as an indicator electrode in the potentiometric method. The amplitude of the potentiometric oscillation increased linearly in proportion to [Ag+] in the range of 9.42 x 10(-6) M to 2.54 x 10(-4) M, with a correlation coefficient of 0.999 under the optimum conditions. The obtained LOD (2sigma) was 8.85 x 10(-6) M and the relative standard deviation (RSD) for five measurements of 1 x 10(-4) M silver ion was 5%. The influence of some potentially interference was also investigated.     

Spectrophotometric study of the complexation of iodine with 1,7-diaza-15-crown-5 in chloroform solution

The complex formation reaction between iodine and 1,7-diaza-15-crown-5 (DA15C5) has been studied spectrophotometrically in chloroform at 25°C. The resulting 1:2 (DA15C5:I₂) molecular complex was formulated as (DA15C5...;I⁺)I ₃ ^– . The spectrophotometric results, as well as the conductivity measurements, revealed that the gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate determining step of the reaction. The rate constant was calculated ask=(8.8±0.2)×10^–3 min^–1. The formation constant of the molecular complex was evaluated from the computer fitting of the absorbance-mole ratio data as logK _f=6.89±0.09.     

Syntheses of [1,2,3]selenadiazolo[4,5‐e]benzofuran or benzothiophene, [1,2,3]thiadiazolo[4,5‐e]benzofuran or benzothiophene,and 2‐benzofuranyl‐1,3,4‐oxodiazole derivatives

Dehydrogenation of ethyl 3‐methyl‐4‐oxo‐4,5,6,7‐tetrahydrobenzofuran‐2‐carboxylate 1 with 2,2′‐azobi‐sisobutyronitrile and N‐bromosuccinimide gave ethyl 4‐hydroxy‐3‐methylbenzofuran‐2‐carboxylate 3 . Reaction of compounds 3–4 with hydrazine hydrate afforded the corresponding hydrazides 5a‐b . The reaction of 5a‐b with aldehydes yielded substituted hydrazones 6a‐l . Compounds 7a‐d were prepared from compounds 6a‐d and bromine in acetic acid. Lead tetraacetate oxidation of compounds 6e‐l afforded substituted oxadiazoles 8e‐l . Selenium dioxide oxidation of 4‐oxo‐4,5,6,7‐tetrahydrobenzofuran semicarbazones 9, 14a and 4‐oxo‐4,5,6,7‐tetrahydrobenzothiophene 14b gave the tricyclic 1,2,3‐selenadiazoles 10, 15a and 15b respectively. Reaction of semicarbazones 9, 14a and 14b with thionyl chloride afforded the corresponding 1,2,3‐thiadiazoles 12, 16a and 16b respectively.     

Synthesis and calcium channel antagonist activities of new derivatives of dialkyl 1,4-dihydro-2,6-dimethyl-4-(5-phenylisoxazol-3-yl)pyridine-3,5-dicarboxylates

The new analogues of nifedipine, in which 2-nitrophenyl group at position 4 is replaced by phenylisoxazolyl substituent, were synthesized. The symmetrical dialkyl 1,4-dihydro-2,6-dimethyl-4-(5-phenylisoxazol-3-yl)pyridine-3,5-dicarboxylates were prepared by classical Hantzsch condensation, and the asymmetrical analogues were synthesized using a procedure reported by Dagnino that involved the condensation of alkyl acetoacetate with alkyl 3-aminocrotonate and 5-phenylisoxazole-3-carboxaldehyde. The structure of all compounds was confirmed by IR, ¹H NMR and Mass spectra. In vitro calcium channel antagonist activities were evaluated as calcium channel antagonists using the high K⁺ concentration of guinea-pig ileum longitudinal smooth muscle (GPILSM) assay. These compounds exhibited moderate calcium antagonist activity (IC₅₀ = 10^?7 to 10^{? 5} M range) relative to the reference drug nifedipine (IC₅₀ = 1.10 ± 0.40 × 10^?8 M).     

Old Reagent,New Results: Aromatization of Hantzsch 1,4-Dihydropyridines with Supported Bismuth Nitrate under Microwave Irradiation in Solventless System

Hantzsch 1,4-dihydropyriines were rapidly and efficiently oxidized using bismuth nitrate supported onto silica gel under microwave irradiation.     

A New Reaction of Isatin,Cyclic 1,3‐Diketone,and 2‐Cyanoacetamide: A Four‐Component Synthesis of Spirooxindoles

A novel reaction of isatins, 2‐cyanoacetamide, and cyclic 1,3‐diketones in ethanol was reported. The reaction gave the unexpected spirooxindole ethyl carboxylates in excellent yields and the spirooxindole carboxamide was not observed.