Formation of Nondendritic Primary Aluminum Phase in Hypoeutectic Alloys in Controlled Diffusion Solidification (CDS): A Hypothesis

Controlled diffusion solidification (CDS) is a novel process wherein specific Al alloys can be cast by mixing two precursor alloys of specific compositions and temperature and subsequently casting the resultant mixture. This process enables a nondendritic morphology of the primary Al phase in the cast samples, which is beneficial in mitigating hot tearing tendencies and enabling castability of dilute Al (wrought) alloys to obtain castings with superior mechanical and performance properties. In this study, a hypothesis is proposed to describe the mechanism of the CDS process, specifically the processes of mixing two precursor alloys and a subsequent solidification process. Al – 4.5 wt pct Cu was used as an example alloy system to propose a hypothesis and to verify the various features in the mechanism of mixing two alloys. Experimental results show that the mixing process naturally causes copious nucleation of one of the alloys mixed and that the turbulence energy during mixing distributes these nuclei uniformly to enable a favorable solidification condition for a nondendritic cast microstructure. It is critical that the alloy with the higher thermal mass (mass and temperature) is mixed into the alloy with lower thermal mass to obtain a valid CDS process and that the reverse will not yield a favorable homogeneous cast sample. Certain critical parameters during the CDS process have also been identified and quantified for a favorable microstructure of the casting.     

New polymer syntheses. IX. Synthesis and properties of new conducting polyazomethine polymers containing main chain cycloalkanone and pyridine moieties

Novel polyazomethines containing cycloalkanones or pyridine moieties were synthesized by the polycondensation of 2,5‐bis(m‐aminobenzylidene)cyclopentanone (BMAP, IV), 2,6‐bis(m‐aminobenzylidene)cyclohexanone (BMAH, V), 2,6‐bis(p‐aminobenzylidene)cyclohexanone (BPAH, VI), and 2,6‐bis(m‐aminostyryl)pyridine (BMAS, VIII) diamines with terephthalaldehyde in EtOH at 25°C. These polymers were yellow to orange in color, had reduced viscosities up to 1.42 dL/g, and had electric conductivities as high as 10⁻¹¹–10⁻¹² S cm⁻¹. All the polyazomethines were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid. However, they were readily hydrolyzed in concentrated H₂SO₄. X‐ray diffraction diagrams showed that the crystallinities of the polyazomethines were low. These azomethine polymers showed high thermal and thermooxidative stability and exhibited no appreciable decomposition up to 400°C in air. The electronic spectra of the polymers indicated a large bathochromic shift of the π–π* absorption band (∼360 nm) that was due to the presence of CN bonds in the polymer main chain. Doping with iodine dramatically raised the conductivity and produced dark brown to black colored semiconductive polymers with a maximum conductivity on the order of 10⁻⁷ S cm⁻¹. Furthermore, the morphology of selected examples of the four polyazomethines was examined by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1218–1229, 2000     

Fabrication,DFT Calculation,and Molecular Docking of Two Fe(III) Imine Chelates as Anti-COVID-19 and Pharmaceutical Drug Candidate

Two tetradentate dibasic chelating Schiff base iron (III) chelates were prepared from the reaction of 2,2′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis(4-bromophenol) (PDBS) and 2,2′-((1E,1′E)-((4-chloro-1,2-phenylene)bis(azanylylidene))-bis(methanylylidene))bis(4-bromophenol) (CPBS) with Fe³⁺ ions. The prepared complexes were fully characterized with spectral and physicochemical tools such as IR, NMR, CHN analysis, TGA, UV-visible spectra, and magnetic moment measurements. Moreover, geometry optimizations for the synthesized ligands and complexes were conducted using the Gaussian09 program through the DFT approach, to find the best structures and key parameters. The prepared compounds were tested as antimicrobial agents against selected strains of bacteria and fungi. The results suggests that the CPBSFe complex has the highest activity, which is close to the reference. An MTT assay was used to screen the newly synthesized compounds against a variety of cell lines, including colon cancer cells, hepatic cellular carcinoma cells, and breast carcinoma cells. The results are expressed by IC50 value, in which the 48 µg/mL value of the CPBSFe complex indicates its success as a potential anticancer agent. The antioxidant behavior of the two imine chelates was studied by DPPH assay. All the tested imine complexes show potent antioxidant activity compared to the standard Vitamin C. Furthermore, the in vitro assay and the mechanism of binding and interaction efficiency of the tested samples with the receptor of COVID-19 core protease viral protein (PDB ID: 6lu7) and the receptor of Gram-negative bacteria (Escherichia coli, PDB ID: 1fj4) were investigated using molecular docking experiments.     

Steel/Mortar interfaces: Mechanical characteristics and electrocapillarity

Measurements of tensile strength of the bond developed between mild steel and various mortars have been made to elucidate the effects of (i) mix characteristics, and (ii) controlled variation in the surface condition of the steel brought about by potentiostatic polarisation. The effects of mix characteristics are attributed to formation of an aggregate-free interfacial zone of segregated hydration products which attains a practically constant structure after a few days of curing. The effects of controlled polarisation of the steel suggest that changes in the properties of its oxide film influence bond in such a way that the observed relationship between bond strength and potential resembles an electrocapillary curve.     

Development of Metal Complexes for Treatment of Coronaviruses

Coronavirus disease (SARS-CoV-2) is a global epidemic. This pandemic, which has been linked to high rates of death, has forced some countries throughout the world to implement complete lockdowns in order to contain the spread of infection. Because of the advent of new coronavirus variants, it is critical to find effective treatments and vaccines to prevent the virus’s rapid spread over the world. In this regard, metal complexes have attained immense interest as antibody modifiers and antiviral therapies, and they have a lot of promise towards SARS-CoV-2 and their suggested mechanisms of action are discussed, i.e., a new series of metal complexes’ medicinal vital role in treatment of specific proteins or SARS-CoV-2 are described. The structures of the obtained metal complexes were fully elucidated by different analytical and spectroscopic techniques also. Molecular docking and pharmacophore studies presented that most of complexes studied influenced good binding affinity to the main protease SARS-CoV-2, which also was attained as from the RCSB pdb (Protein Data Bank) data PDB ID: 6 W41, to expect the action of metal complexes in contradiction of COVID-19. Experimental research is required to determine the pharmacokinetics of most of the complexes analyzed for the treatment of SARS-CoV-2-related disease. Finally, the toxicity of a metal-containing inorganic complex will thus be discussed by its capability to transfer metals which may bind with targeted site.     

Performance of the simulated annealing and genetic algorithms for the design of periodic devices

The performance of the simulated annealing and genetic algorithms is investigated when used for microwave device design. A finite-element method for 2D structures having 1D periodicity is used to generate the objective function used in the optimization. A comparison of the optimization algorithms is described based on a number of design examples. © 1997 John Wiley & Sons, Inc. Int J Microwave Millimeter-Wave CAE 7: 108–116, 1997.     

Enhanced oil/water separation via electrospun poly(acrylonitrile-co-vinyl acetate)/single-wall carbon nanotubes fibrous nanocomposite membrane

In this study, poly(acrylonitrile-co-vinyl acetate) (P(AN-co-VA)) reinforced by 0.1, 0.5, and 1.0% w/w functionalized single-wall carbon nanotubes (SWCNTs), fibrous nanocomposites were fabricated using electrospinning technique. Functional analysis revealed the presence of hydroxyl band which is characteristic of the carboxylated SWCNTs. Morphological analysis manifested neatly uniform nanofibers with an average fiber diameter varying from 62 to 308 nm depending on the processing conditions of electrospinning. Contact angle measurements showed a decline in the contact angle by increasing carboxylated SWCNTs contents. Oil/water separation was assessed using dead-end module under different testing conditions and showed an excellent performance. The maximum rejection ratio for the oil/water separation test for the electrospun fibrous nanocomposite was about 97.5% for 0.5 wt% carboxylated SWCNTs. These results conveyed the promising performance of electrospun P(AN-co-VA)/SWCNTs nanocomposite membranes for oil/water separation technology.     

Economic and environmental evaluations of dedicated and residential electric tariffs for plug‐in electric vehicles

Plug‐in electric vehicle (PEV) owners may have multiple different electric tariffs offered by their local utility companies from which to choose. The offered PEV tariffs are designed mainly to shift the electric demand for charging cars to the time when the grid is less strained. This paper investigates both the economic and the environmental impacts of adopting dedicated PEV electric tariffs from the PEV owners' perspective. The overall conclusion is that the dedicated tariffs are well designed for PEVs from the economical perspective but not from the environmental perspective. Case studies of the cost minimization model show that on average the dedicated PEV tariffs will result in approximately half the cost of the electric bill and slightly lower greenhouse gas (GHG) emissions (less than 1%) compared with the standard flat‐rate residential tariffs. Case studies of the emission minimization model show that the GHG emissions can be reduced by 10.47% as compared with the cost minimization model, but this will lead to an increase in the total charging cost that can be as high as 15.44% on average.     

Experimental Investigation and Analysis of the Settlement Funnel in Beds Supporting Different Types of Foundations

A solution is given for determination of the stresses in a foundation bed, which is represented by a linearly deformable half space and intended for foundations with circular or square lower surfaces extending beyond the limits of the loaded area. Experimental data on the settlement funnel in homogeneous and layered beds are presented. The dependence of the spread of the settlement funnel on the dimensions of the plate is established.     

Time-averaged heat transfer correlation for direct injection hydrogen fueled engine

This paper presents the development of an empirical correlation for the prediction of time-averaged heat transfer for a direct-injection hydrogen fueled engine. Computer simulation based on one-dimensional gas dynamics approach was used to perform the time-averaged analysis for the in-cylinder heat transfer. Simulation was performed for 1800 ≤ rpm ≤ 5000, 0.2 ≤ φ ≤ 1.2 and 130 deg before top dead center (BTDC) ≤ SOI ≤ 70 deg BTDC. Experimental measurements were used to verify the developed model, during which the engine performance could be determined to a reasonable accuracy of 10%. The equivalence ratio (φ) was considered as a governing variable, through the new correlation for the time-averaged heat transfer. A nonlinear regression approach was used to develop the new correlations. In the case of all the simulation data, the proposed correlations have a satisfactory performance with the determination coefficient (R²) of about 0.99. A relative error of 10% was found in more than 95% of the simulation data. However, the relative error was reduced to about 50% in the newly developed correlations, which increased its reliability to more than the Taylor's correlation for representing the actual data. Due to the general form, hydrocarbon fuel is suitable for the newly developed correlations that are theoretically made.