CubeSat formation architecture for small space debris surveillance and orbit determination

Introduction: Satellites which face space debris cannot track it throughout the whole orbit due to natural limitations of their optical sensors, sush as field of view, Earth occultation, or solar illumination. Besides, the time of continuous observations is usually very short. Therefore, we are trying to offer the most effective configuration of optical sensors in order to provide short-arc tracking of a target piece of debris, using a scalable Extended Information Filter. Purpose: The best scenario for short-arc tracking of a space debris orbit using multipoint optical sensors. Results: We have found optimal configurations for groups of satellites with optical sensors which move along a sun-synchronous orbit. Debris orbit determination using an Extended Information Filter and measurements from multipoint sensors was simulated, and mean squared errors of the target's position were calculated. Based on the simulation results for variouos configurations, inter-satellite distances and measurement time, the most reliable scenario (four satellites in tetrahedral configuration) was found and recommended for practical use in short-arc debris tracking.

Decentralized Control of Nanosatellite Tetrahedral Formation Flying Using Aerodynamic Forces

A decentralized control algorithm for the construction of a tetrahedral configuration using differential lift and drag forces is proposed in this paper. Four 3U CubeSats launched in LEO are considered. Satellite attitude-controlled motion relative to the incoming airflow provides the required differential forces in order to change the relative translational motion. The developed control algorithm allows one to track the relative reference trajectories for the satellites at the vertices of the tetrahedron of the required shape and size. The influence of the initial launch conditions on the controlled tetrahedral motion is studied in this paper.

Study of Pc5 compressional waves by MMS observations

<p>Pc5 compressional waves are frequently observed in the outer magnetosphere with mirror mode features. Due to the limited spatial coverage of spacecraft, their overall structure is still poorly understood. In this work, the wave structure and motion characteristics are statistically investigated based on the MMS data from September to October 2015. During this time period, the apogees of the MMS spacecraft were located in the outer dusk magnetosphere, and the spacecraft has regular tetrahedral configuration that facilitates the application of multi-spacecraft analysis techniques. The magnetic trough boundaries are identified, and their normal direction, current density and velocity of these boundaries are calculated. We found that the magnetic trough has a magnetic bottle topology along the field line. In the r-a plane, the two boundaries has an open angle toward the radial direction.The boundaries mainly move sunward in the GSE XY plane with average speed of ~26km/s. The poloidal Alfven mode is found to be coupling with the compressional mode oscillation. It suggests that our observations could be explained by the theory of drift Alfven ballooning mirror instability.</p>

A New Modular Structural System for Tall Buildings Based on Tetrahedral Configuration

Inspired by the high mechanical performance of diagrid structures, the minimization of material consumption on braced tubes and the expressive potency of tensegrity modular structures, this work proposes an innovative three-dimensional system for tall buildings. A new modular structural system generated from the assembly of tetrahedral units is investigated. The paper integrates insights on the architectural implications and mechanical performance of the reticular system arranged in repetitive triangular-based modules. The impact of different geometric configurations of the structural members on the economic design is also discussed and recommendations for the optimal topology are made. Guidelines for the design and analytical formula for accessing preliminary member sizes are proposed on the basis of stiffness requirements.

One new copper iodide coordination polymer directed by 4-pyridyl dithioether ligand: Syntheses, structures, and photocatalysis

One new compound consisting of 1,1-bis(4-pyridylthio)methylene ([Bpytm]) ligand, namely [Bpytm]CuI (1), has been prepared and characterized by IR spectroscopy, solid Uv-visible diffuse reflectance spectrum, and X-ray Powder Diffraction (PXRD). Compound 1 is a 2D MOF and ligand [Bpytm] coordinate with metal ions to form tetrahedral configuration. For compound 1: Crystal system: Monoclinic, Space group: C2/c, a = 13.6671(11), b = 11.6075(11), c = 17.1225(12), α= 90°, β= 93.707(3)°, γ= 90°, V = 2710.6(4) Å3, Z = 8, Dcalc = 2.082 g cm–3. The photocatalytic properties and thermal stability have been researched.

SYNTHESIS AND STRUCTURE OF ORGANYLTRIPHENYLPHOSPHONIUM DICYANOARGENTATES: [Ph3P(CH2)3PPh3]2+ [Ag(CN)2]– [Br]– AND [Ph3PR]+ [Ag(CN)2]–, R = CH2CH2OH, CH2C6H4F-4

The reaction of potassium dicyanoargentate with organyltriphenylphosphonium bromides in an aqueous solution has led to synthesis of complexes [Ph3P(CH2)3PPh3]2+[Ag(CN)2]–[Br]– (1), [Ph3PR]+[Ag(CN)2]–, R = CH2CH2OH (2), CH2C6H4F-4 (3), whose structures have been characterized by X-ray diffraction analysis (XRD). It is known that the absorption range of cyano groups in IR spectra of organic and inorganic compounds is in the form of a narrow interval of 2200-2000 cm-1, which points at the absence of strong surroundings influence on vibrations of these bonds. The absorption bands in the range 1450-1435 cm-1 peculiar to the P-Ph bands that are present in the spectra of compounds 1, 2, 3 are apparent in the range 1437-1439 cm-1. The XRD data have been obtained at 293 K on a Bruker D8 QUEST automatic four-circle diffractometer: crystals 1 (C41H36AgBrN2P2, М 806.44, triclinic syngony, crystal size 0.72 × 0.37 × 0.3 mm), 2 (C22H20AgN2OP, M 467.24, triclinic syngony, crystal size 0.8 × 0.52 × 0.35 mm), 3 (C27H21AgFN2P, M 531.30, monoclinic syngony, crystal size 0.28 × 0.23 × 0.22 mm). According to the XRD data, crystals 1, 2, 3 contain organyltriphenylphosphonium cations and linear dicyanoargentate anions. Besides, bromide anions are observed in crystal 1. A characteristic feature of complexes with the [Ag(CN)2]− anions is their perspective utility for development of new nano- and liquid crystal systems. The organyltriphenylphosphonium cations have a distorted tetrahedral configuration: the CPC angles vary within the range 106.70(8)° - 113.37(9)°. In the [Ag(CN)2]−anions the CAgC angles equal 171.75(10)° – 178.37(8)°.

SYNTHESIS AND STRUCTURE OF (METHOXYMETHYL)TRIPHENYLPHOSPHONIIUM TRICHLORO(DIMETHYLSULFOXIDO)PLATINATE

(Methoxymethyl)triphenylphosphonium trichloro(dimethylsulfoxido)platinate [Ph3PCH2OCH3][PtCl3(dmso-S)] was synthesized by the reaction of hexachloroplatinic acid with (methoxymethyl)triphenylphosphonium chloride in dimethyl sulfoxide. During the reaction, Pt (IV) was reduced to Pt (II). The reactions are accompanied by the ligand exchange in anions with substitution of the S-coordinated dimethyl sulfoxide molecule for one of chlorine atoms. Slow evaporation of the solvent led to the formation of large orange crystals. The product structure was determined by XRDA. The structures were interpreted by the direct method. Positions and temperature parameters of non-hydrogen atoms were refined in isotropic and then in anisotropic approximations by the full-matrix LSM. The X-ray diffraction pattern of crystal I was carried out on a Bruker D8 QUEST diffractometer. According to the data of X-ray analysis the unit cell crystallographic parameters of compound I are [crystal system monoclinic, space group P21/c, M 686.90, a 14.48(2), b 14.48(2), c 19.99(3) Å]. The tetrahedral configuration of the (methoxymethyl)triphenylphosphonium cation approaches the ideal values (CPC angles are 108.5(2)°-110.3(2)°, bond lengths Р-С are slightly differ from each other). Platinum atoms in anions have square coordination (trans-arranged angles ClPtCl are 177.65(5)°, SPtCl are 178.88(6)°, cis-angles approach 90°). The bond lengths Pt–Cl are equal to 2.290(3)–2.314(3) Å, Pt–S are equal to 2.205(3) Å. The platinum atoms are coordinated by three chlorine atoms and dimethyl sulfoxide molecule in the anion. Dimethyl sulfoxide molecule is coordinated to the platinum atoms by sulfur atoms. The geometry of the coordinated dimethyl sulfoxide ligand [OSC and СSC angles, S−O bond] differs from the geometry of a free dimethyl sulfoxide molecule.

Multi-targeted Antisense Oligonucleotide Delivery by a Framework Nucleic Acid for Inhibiting Biofilm Formation and Virulence

Biofilm formation is responsible for numerous chronic infections and represents a serious health challenge. Bacteria and the extracellular polysaccharides (EPS) cause biofilms to become adherent, toxic, resistant to antibiotics, and ultimately difficult to remove. Inhibition of EPS synthesis can prevent the formation of bacterial biofilms, reduce their robustness, and promote removal. Here, we have developed a framework nucleic acid delivery system with a tetrahedral configuration. It can easily access bacterial cells and functions by delivering antisense oligonucleotides that target specific genes. We designed antisense oligonucleotide sequences with multiple targets based on conserved regions of the VicK protein-binding site. Once delivered to bacterial cells, they significantly decreased EPS synthesis and biofilm thickness. Compared to existing approaches, this system is highly efficacious because it simultaneously reduces the expression of all targeted genes (gtfBCD, gbpB, ftf). We demonstrate a novel nucleic acid-based nanomaterial with multi-targeted inhibition that has great potential for the treatment of chronic infections caused by biofilms.

SYNTHESIS AND STRUCTURE OF METHYLTRIPHENYLPHOSPHONIUM DICYANODIBROMOAURATE [Ph3PCH3] [Au(CN)2Br2]

Methyltriphenylphosphonium dicyanodibromoaurate (1) [Ph3PMe]+[Au(CN)2Br2]– was synthesized by the reaction of potassium dicyanodibromoaurate with methyltriphenylphosphonium bromide in an aqueous solution and was structurally characterized. The complex is a yellow-colored, air-resistant crystalline substance with a clear melting point. The structure of the compound was established by IR spectroscopy, NMR spectroscopy and X-ray diffraction analysis. An intense absorption band was observed in the IR spectrum of compound at 2220 cm−1, corresponding to the stretching vibrations of cyano groups. The absorption band of the deformation vibrations of the P – СPh bonds in the IR spectrum is at 1438 cm−1. In the recorded 1Н, 13С, and 31Р NMR spectra, signals are observed for the number, value of chemical shifts and integral intensity that do not contradict the proposed complex structure. The X-ray diffraction analysis of crystal 1 was carried out on a Bruker D8 QUEST diffractometer (MoKα radiation, λ = 0.71073 Å, graphite monochromator). [C21H18AuBr2N2P, M = 686.13, crystal system triclinic, space group P-1, a = 8.802(5), b = 8.989(5), c = 15.233(11) Å, V = 1143.8(13) Å3, Z = 2, µ = 10.002 mm-1, F(000) = 644, crystal size 0.41×0.30×0.22 mm]. According to the X-ray diffraction analysis (XRDA) data there are two types of centrosymmetric crystallographically independent monomeric dicyanodibromoaurate anions and methyltriphenylphosphonium cations in the crystal of compound MFDDA. The cations have a distorted tetrahedral configuration: the CPC angles equal 108.8(2)°−110.0(2)°, the P−С distances are 1.791(5)−1.800(5) Å. All СAuC and BrAuBr trans-angles are 180.0° in the [Au(CN)2Br2]− anions. The Au−C distances in anions differ from each other and equal 2.040(7), 2.024(1), 1.991(2) Å. These values are close to the sum of the covalent radii of atoms (2.03 Å). The Au-Br bond lengths are equal to 2.4162(14), 2.4591, 2.474(5) Å in dicyanodibromoaurate anions. Formation of the crystal structure occurs due to formation of weak N···Н−С hydrogen bonds between cations and anions (2.68, 2.59, 2.38 Å) and Br···Н−С (3.03, 3.02 Å). Complete tables of coordinates of atoms, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Centre.

Synthesis, identification and thermal study of some new inorganic polymers based on bis-dithiocarbamate ligands with silicone, tellurium and some transition metals

Introduction: In recent years, there has been considerable interest in dithiocarbamate complexes because of its diverse biological roles, very few reports have been made on polymeric bis- dithiocarbamate compounds with carbon chain of n-propyl or hexamethelene with transition metals in addition of the absence of any report of organosilicone or tellurium halides with such compounds Our interest in this report based on the preparation of new series of polymers with an expected activity as a fungi side compounds followed by the using of prepared amino compound as a hardners for epoxy paints Materials and Methods: A new polymers of the general structures –(MS2CNH(CH2)6NHCS2M-)n where [M= Cu, Cd, Mn and Zn] and –(M(R)2S2CNH(CH2)nNHCS2MR2-)m where [M= Si,R=CH 3 , n= 2 ,3 and 6 ; M=Te , R= Br , n= 2 ,3 and 6 ; M=Co, Ni R=Cl ; n= 6] have been prepared by reaction of MX2 where M= Ni ,Co, Cd , Mnor Zn , X= Cl ; M=Cu , X= SO4 , and dimethyl dichloro silane, tellurium tetrabromide with the corresponding sodium salts of bis-dithiocarbamateligands. Results and Discussion: Dimethyldichloro silane is a very sensitive material to O-H group, in addition to that, TeBr4 decomposed rapidlyin water so, a series solvents may be useful with such sensitive chemicals to water , in the other hand, dithiocarbamate ligands which is usually prepared in aqueous and alcoholic solution , must be prepared and isolated carefully to apply the other steps of synthesis using a chloroform solution as a solvent. It seems for the first view for dithiocarbamato ligands it may act as a bi dentate ligands using two sulphur donating atoms that is clearly appeared in common complexes such as diethyl dithiocarbamato or pipyridyl, morpholino dithiocarbamato with representation metal elements, even in such type of elements a sulfur bridges may formed. In this study, it showed clearly that Zinc and Cadimium polymers are diamagnetic polymers that is mean that these polymers are with oxidation state equal to (II) and a tetrahedral configuration Conclusions: The study showed that the new silicone polymers act as a stable polymers compared with others. All new polymers are of a high stability with large values of char contain with commercial epoxy. Among silicone polymers, the polymerwith carbon chain equal to 3 is more stable than that with 2 carbon atoms while the silicone polymer with 6 carbon atoms is the less stable one, may thermal treatment caused decomposition combined.