Tonal prediction of a faulty axial fan

The current techniques for monitoring and diagnostics of rotating machines to their conditional predictive maintenance mainly are based on vibration monitoring. In this research, experimental and theoretical methods to predict the tonal noise of a faulty fan are developed and validated. These methods can be used on identifying defects of an axial fan based on an acoustic monitoring in situations where it is necessary to operate remotely due to the inaccessibility of the areas of event defects.     

Elaboration and characterization of organic–inorganic quantum wells impregnated on porous anodic alumina nanostructures

An organic–inorganic quantum well embedded on porous anodic alumina was synthesized and studied by MEB, AFM, optical absorption and photoluminescence. The morphology determined by the MEB and the AFM, shows that the size of the pores is about 10 nm for alumina evaporated on glass substrate and about 35 nm for alumina template prepared in sulfuric acid (H₂SO₄). The optical properties are characterized from absorption and photoluminescence spectra measured at room and low temperature. The measured spectral characteristics demonstrate the influence of the pore size on the emission of the organic–inorganic quantum well ((C₁₂H₂₅NH₃)₂PbI₄). An obvious blueshifted photoluminescence (PL) of (C₁₂H₂₅NH₃)₂PbI₄ in nanometer-sized pores was observed. It results in a better quantum confinement.     

Key factor affecting the basicity of mesoporous silicas MCM-41: effect of surfactant extraction time and Si/Al ratio

Mesoporous silica Si-MCM-41 was prepared by hydrothermal method using TEOS and CTAB as the source of silica and structuring agent, respectively. The surface of the as-synthesized material was treated using HCl/ETOH solvent to remove the CTA surfactant instead of using the calcination. Characterization of the catalysts was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen sorption at 77 K, scanning and transmission electronic microscopy (SEM, TEM), and thermogravimetric analysis TGA. The catalytic properties of the prepared materials in the condensation of acetophenone with ethyl cyanoacetate were studied. The effects of the catalyst type, Si/Al ratio, reaction kinetics, and reaction temperature were also investigated to find an optimal parameter. The results show that an interesting yield was obtained (about 96%) in a short reaction time; it is found that the yields of products depend not only on the amount of surfactant inside the mesopores but also on the Si/Al ratio. The catalyst reuse shows that this catalyst can be used up to five cycles, and at temperatures higher than 50 °C, the yield of products decreases due to the slight destruction of the catalyst as confirmed by the XRD analysis. Based on the results obtained, a possible mechanism of the condensation reaction of acetophenone was proposed.     

Lewis acid-catalyzed Csp3–H functionalization of methyl azaarenes with α-trifluoromethyl carbonyl compounds

A Lewis acid promoted Csp³–H bond functionalization of methyl azaarenes with α-trifluoromethylated carbonyl compounds is described. Catalytic amounts of Yb(OTf)₃ provided a straightforward access to the corresponding trifluoromethylated alcohols in excellent yields up to 94% under mild reaction conditions.     

The Synthesis and Characterization of a New Cobalt Dimethylphenylpiperazinium Cyclotetraphosphate Hexahydrate,Co[C12 H19 N2]2 P4 O12.6 H2 O

Cobalt dimethylphenylpiperazinium cyclotetraphosphate hexahydrate, Co[C₁₂H₁₉N₂]₂P₄O₁₂.6H₂O, was synthesized by a reaction between cyclotetraphosphoric acid H₄P₄O₁₂, cobalt carbonate, and 1-(2,4-dimethylphenylpiperazine). It crystallizes in the triclinic system, space group P, with the following unit cell parameters: a = 7.336(1), b = 8.413(1), c = 14.926(2) Å, α = 87.46(1), β = 83.13(1), γ = 82.98(1)°, V = 907.3(2) ų, and Z = 1. The atomic arrangement can be described as layers containing P₄O₁₂ rings a and Co(H₂O)₆ octahedra spreading in the (001) planes between which are located the dimethylphenylpiperazinium groups via H-bonds. The synthesis and characterization by X-ray diffraction, IR absorption, and thermal analysis are described.     

Synthesis and Structural Characterization of a Novel Cyclotetraphosphate

The crystal structure of (2-NH₂-5-ClC₅H₄N)₄P₄O₁₂.6H₂O was determined by X-ray diffraction on a single crystal. This compound crystallizes in an orthorhombic unit cell Pccn with the parameters a = 25,387(7) Å, b = 15,756(6) Å, c = 9,750(5) Å, V = 3900(2) ų, Z = 4, and D _x = 1,605 g.cm^?3. Crystal structure has been determined and refined to R = 0,036, using 7678 independent reflexions. This structure can be described as inorganic layers stacked along a-direction and held together through N-H… O hydrogen bonds, originating from the organic cations, giving rise to three-dimensional H-bonded assemblies. In addition, in this structure there is electrostatic, van der Waal forces and Cl… Cl interaction so as to increase the cohesion of 3D-network. Chemical preparation and characterization by RX diffraction, IR absorption, and thermal analysis are described.     

Electronic structure calculations and optical properties of a new organic-inorganic luminescent perovskite: (C9H19NH3)2PbI2Br2

(C₉H₁₉NH₃)₂PbI₂Br₂ compound is a new crystal belonging to the large hybrid organic-inorganic perovskites compounds family. Optical properties are investigated by optical absorption UV-visible and photoluminescence (PL) techniques. Bands to band absorption peak at 2.44 eV as well as an extremely strong yellow-green photoluminescence emission at 2.17 eV is observed at room temperature. First principle calculations based on the DFT and FLAPW methods combined with LDA approximation are performed as well. Density of state close to the gap is presented and discussed in terms of optical absorption and photoluminescence experimental results. The perfect agreement between experimental data and electronic structure calculations is highlighted.     

A Pyrimidopyrimidine Janus‐AT Nucleoside with Improved Base‐Pairing Properties to both A and T within a DNA Duplex: The Stabilizing Effect of a Second Endocyclic Ring Nitrogen

Janus bases are heterocyclic nucleic acid base analogs that present two different faces able to simultaneously hydrogen bond to nucleosides that form Watson–Crick base pairs. The synthesis of a Janus‐AT nucleotide analogue, ^N J_AT , that has an additional endocyclic ring nitrogen and is thus more capable of efficiently discriminating T/A over G/C bases when base‐pairing in a standard duplex‐DNA context is described. Conversion to a phosphoramidite ultimately afforded incorporation into an oligonucleotide. In contrast to the first generation of carbocyclic Janus heterocycles, it remains in its unprotonated state at physiological pH and, therefore, forms very stable Watson–Crick base pairs with either A or T bases. Biophysical and computational methods indicate that ^N J_AT is an improved candidate for sequence‐specific genome targeting.     

Synthesis,Enzyme Inhibition,and Molecular Docking Studies of Hydrazones from Dichlorophenylacetic Acids

A series of hydrazones 5a–i were synthesized by the condensation of hydrazides derived from dichlorophenylacetic acids with different aromatic aldehydes and ketones. Their structures were confirmed by spectroscopic data and elemental analysis. Hydrazones 5a–i were evaluated for α‐glucosidase and urease inhibition activities. Five compounds exhibited potent α‐glucosidase inhibitory potential with IC₅₀ values 8.5 ± 0.3, 22.2 ± 0.78, 32.9 ± 1.5, 34 ± 2.4, and 170.6 ± 7.5 μM, respectively, which are many times better than that of the standard inhibitor acarbose (IC₅₀ = 840 ± 1.73 μM). Furthermore, molecular docking study was performed to explore the binding mode in the active sites of α‐glucosidase and urease enzymes.