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.

     

DFT computational study towards investigating Cladribine anticancer drug adsorption on the graphene and functionalized graphene

Structural Chemistry - Density functional theory calculations at the M06-2X/6-31G** level have been carried out to examine the adsorption behavior of Cladribine drug on the graphene and graphene...     

The Possibility of Wax Formation in Gas Fields： a Case Study

Natural gas production from a gas reservoir(Reservoir A)located in the south of Iran,presents solids deposition during processing because the condensate contains suspended and dissolved solids.Solids deposition occurs not only in the transportation lines from the wells to the separators but also in the various operating units of gas streams and condensate stream.In this study,the multisolid-phase model has been used to predict the wax precipitation from gas and gas condensate fluids.The properties of gas and liquid phases are described using the Soave-Redlich-Kwong(SRK)equation of state.The model is then used to predict the possibility of the wax formation in Reservoir A gas facilities,located at the south of Iran.Solid deposition which occurred in the various streams of that facility confirmed the calculated results.Finally,the wax appearance temperature(WAT),the weight percent of wax formation and the effects of pressure and temperature on the wax formation were also predicted.     

Antimicrobial activity of nanocellulose conjugated with allicin and lysozyme

In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC₅₀ and MIC₉₀ was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials.     

Heteropolyacid as a New,Green and Recyclable Catalyst for the Synthesis of 2‐Aryl Benzoxazole under Solvent‐Free Conditions

A simple, convenient and general method has been developed for the synthesis of 2‐arylbenzoxazole via condensation of o‐aminophenols and benzoyl chloride derivatives under solvent‐free conditions in the presence of a catalytic amount of heteropolyacids in good yields.     

Computational and experimental study on the interaction of three novel rare earth complexes containing 2,9-dimethyl-1,10-phenanthroline with human serum albumin

In this paper, several rare earth [terbium(III), ytterbium(III) and yttrium(III)] complexes containing 2,9-dimethyl-1,10-phenanthroline (Me₂Phen) were successfully synthesized and characterized by means of elemental analysis (CHN), infrared spectroscopy (FT-IR), UV–vis absorption spectroscopy and ¹HNMR. To explore the potential medicinal value of these complexes (MMe₂Phen), their binding interactions with human serum albumin (HSA) were investigated through UV–vis and fluorescence spectroscopies and also molecular docking examinations. The thermodynamic parameters, binding forces and Förster resonance distance between these complexes and Trp-214 of HSA were estimated from the analysis of fluorescence measurements. The values of estimated binding constants (K_b) ranging for the formation of MMe₂Phen:HSA complex were in the order of 10⁵ M^?1. The thermodynamic parameters determined by van’t Hoff analysis of K_b (ΔH°?<?0 and ΔS°?<?0) clearly indicate the major rules of hydrogen bonds and van der Waals interactions in the formation process of MMe₂Phen:HSA. The values of Stern–Volmer constant and the evaluation of dynamic quenching constant at various temperatures provided good evidences for static quenching mechanism. Furthermore, the results of molecular docking calculation and competitive binding experiments represent the binding of these complexes to site 3 of HSA located in subdomain IB, containing both polar and apolar residues. The consistency of computational and experimental results, according to the binding sites and the order of binding affinities (TbMe₂Phen?>?YbMe₂Phen?>?YMe₂Phen), supports the accuracy of docking calculation.     

Temperature-induced aggregation ionic liquid dispersive liquid-liquid microextraction method for separation trace amount of cobalt ion

A simple and rapid temperature induced aggregation micro extraction method based on ionic liquid for extraction and preconcentration of cobalt ions from water samples was proposed. In this investigation small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆] and 1-hexyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide [Hmim][Tf₂N] (as extractant solvents) were added in a sample solution containing Triton X-114 (as an anti-sticking agent). After centrifuging the cooled solution, analysis was carried out by flame atomic absorption spectrophotometry. Some effective parameters have been optimized. Under the optimum conditions, detection limit of the method was 0.44 ng/mL and the relative standard deviation (RSD) for 100.0 ng/mL cobalt was ±2.3% (n = 7).The calibration curve was linear in the range of 3.0–200.0 ng/mL cobalt and enrichment factor was obtained as 26.5. The applicability of the technique was evaluated by the determination of trace amounts of cobalt in several water samples and synthetic alloys.     

Characterization of the structural changes of human serum albumin upon interaction with single-walled and multi-walled carbon nanotubes: spectroscopic and molecular modeling approaches

Research on Chemical Intermediates - Through the incorporation of spectorescopic and molecular methods of modeling, the researchers investigated the interaction between Carbon Nanotubes (CNTs) and...