Stereoselective synthesis of conformationally constrained tropane analogues: 6‐Chloro‐2,5‐diazatetracyclo[8.5.0.02,13.04,9]pentadeca‐4,6,8‐triene‐11‐one and 6‐chloro‐2,7‐diazatetracyclo‐[8.5.0.02,13.04,9]pentadeca‐4,6,8‐triene‐11‐one

Two conformationally constrained tropane derivatives were prepared as rigid nicotinic acetylcholine receptor ligands. A palladium catalyzed intramolecular α‐arylation reaction was employed to generate the tricyclic compounds in good yields from N‐(bromo‐chloropyridylmethyl)‐8‐azabicyclo[3.2.1]octan‐3‐ones.     

Nickel(II) complexes prepared from NNN type ligands and pseudohalogens

Six nickel(II) complexes, using azide and thiocyanate ions, have been synthesized from bis-2,6(pyrazol-1-yl)pyridine (pp) and some methyl derivatives, 2-(3,5-dimethyl(pyrazol-1-yl)-6-(pyrazol-1-yl)pyridine (app) and bis-2,6(3,5-dimethyl(pyrazol-1-yl) pyridine (dmpp) in non-aqueous media. The complex structures were analyzed using elemental analysis, IR spectroscopy and thermogravimetry. Appropriate crystals of complex, containing azide [Nipp(N₃)₂]·MeOH (I) and thiocyanate [Nidmpp(SCN)₂·MeOH] (VI) were prepared and the molecular structures determined using X-ray diffraction. Complex I was seen to be dinuclear as stated in literature, space group P2₁/n, monoclinic, a=10.503, b=10.681, c=13.291 Å, β=106.56° and Z=2 whereas complex VI was found to be mononuclear, space group P2₁/n, monoclinic, a=8.646, b=12.614, c=20.697 Å, β=97.18° and Z=2. The Ni(II) coordination in both complexes were octahedral. Thermogravimetric studies showed azide containing structures to resemble the characteristics of explosive materials. Coordinative MeOH were seen to leave the structure in thiocyanate containing complexes, followed by irregular degradation above 300°C.     

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

Journal of Thermal Analysis and Calorimetry - To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the...     

Atomic layer deposition as pore diameter adjustment tool for nanoporous aluminum oxide injection molding masks

The wetting properties of polypropylene (PP) surfaces were modified by adjusting the dimensions of the surface nanostructure. The nanostructures were generated by injection molding with nanoporous anodized aluminum oxide (AAO) as the mold insert. Atomic layer deposition (ALD) of molybdenum nitride film was used to control the pore diameters of the AAO inserts. The original 50-nm pore diameter of AAO was adjusted by depositing films of thickness 5, 10, and 15 nm on AAO. Bis(tert-butylimido)-bis(dimethylamido)molybdenum and ammonia were used as precursors in deposition. The resulting pore diameters in the nitride-coated AAO inserts were 40, 30, and 20 nm, respectively. Injection molding of PP was conducted with the coated inserts, as well as with the non-coated insert. Besides the pore diameter, the injection mold temperature was varied with temperatures of 50, 70, and 90 degrees C tested. Water contact angles of PP casts were measured and compared with theoretical contact angles calculated from Wenzel and Cassie-Baxter theories. The highest contact angle, 140 degrees , was observed for PP molded with the AAO mold insert with 30-nm pore diameter. The Cassie-Baxter theory showed better fit than the Wenzel theory to the experimental values. With the optimal AAO mask, the nanofeatures in the molded PP pieces were 100 nm high. In explanation of this finding, it is suggested that some sticking and stretching of the nanofeatures occurs during the molding. Increase in the mold temperature increased the contact angle.     

Electron-related optical responses in triple δ-doped quantum wells

A detailed theoretical study on the electron-related optical responses in triple δ-doped GaAs quantum wells in the presence of non-resonant, monochromatic intense laser field is presented. For this purpose, we first obtained the bound subband energy levels and their corresponding envelope wave functions of the structure for different central doping concentrations within the effective-mass approximation. Then, we calculate the effect of the non-resonant intense laser field on the optical properties of this structure using the compact-density-matrix approach via the iterative method. We found that the optical absorption coefficients and refractive index changes in the triple δ-doped GaAs quantum well can be modulated by changing the central doping concentration and the intensity of the non-resonant, monochromatic laser field. In addition, it is shown that a sufficiently intense laser field suppresses the multiple quantum well configuration towards a single potential well one and the optical response becomes practically independent of the δ-doping concentration.     

Anisotropic adaptive stabilized finite element solver for RANS models

Aerodynamic characteristics of various geometries are predicted using a finite element formulation coupled with several numerical techniques to ensure stability and accuracy of the method. First, an edge‐based error estimator and anisotropic mesh adaptation are used to detect automatically all flow features under the constraint of a fixed number of elements, thus controlling the computational cost. A variational multiscale‐stabilized finite element method is used to solve the incompressible Navier‐Stokes equations. Finally, the Spalart‐Allmaras turbulence model is solved using the streamline upwind Petrov‐Galerkin method. This paper is meant to show that the combination of anisotropic unsteady mesh adaptation with stabilized finite element methods provides an adequate framework for solving turbulent flows at high Reynolds numbers. The proposed method was validated on several test cases by confrontation with literature of both numerical and experimental results, in terms of accuracy on the prediction of the drag and lift coefficients as well as their evolution in time for unsteady cases.     

Modification of polypropylene surfaces with micropits and hierarchical micropits/nanodepressions

Micropit surfaces and hierarchically structured micropit/nanodepression surfaces were fabricated in polypropylene by injection moulding. The first step in the process was the microstructuring of aluminium foils with a micro-working robot to obtain a pattern of micropits. Dimensions of the micropits could be controlled by adjusting the working parameters of the robot. The microstructured faces of some of the foils were anodized to aluminium oxide giving a surface in which both micropits and the smooth areas between were covered with nanopores. Mould inserts for the injection moulding were obtained by cold mounting of an epoxy resin mixture on the foils. After the epoxy resin had hardened, the foils were etched away. Dimensions of the micropillars and micropillars/nanobumps on the epoxy related to the dimensions of the structures on the foils. Finally, structures were replicated in polypropylene as micropits and hierarchical micropits/nanodepressions by injection moulding. The dimensions of these hollow structures corresponded well with those of the epoxy pillars and the original micropits.Static and dynamic contact angles on the micropit-structured polypropylene surfaces were elevated from the slightly hydrophobic values of smooth polypropylene. With hierarchical micropit/nanodepression structures, the contact angles approached the superhydrophobic limit of 150°. The work demonstrates an inexpensive and reproducible technique to fabricate hollow structures of various dimensions and scales on polypropylene and modify the surface properties of the polymer.