New processable polyaromatic amides curable by Diels-Alder cycloaddition

New processable polyaromatic amides were prepared from the acid chloride of bis-m-carboxyphenyl acetylene (V), the acid chloride of 1,4-bis-m-carboxyphenyl-1,3-butadiene (VI), and several aromatic diamines. The polyamides that contained acetylene units were cured by Diels-Alder cycloaddition reaction with 1,4-diphenyl-1,3-butadiene, whereas the polyamides with 1,3-butadiene units were cured with N-phenyl maleimide. Cured polyamides showed an increase in t_g, thermal, and heat stabilities. The polyamides can be cast into films and produce good glass-fiber laminates.     

Calculation of optimum geometries and force fields by the CNDO/force method

CNDO/Force calculations have been performed on a series of molecules, H₂CO, F₂CO, CF₄, CHF₃, CH₂F₂ and CH₃F. The optimum geometries and force fields are reported. It is found that the method can successfully predict the geometries of polyatomic molecules. The bending force constants and interaction force constants are, in general, comparable with experimental values both with respect to sign and magnitude. The stretching force constants have higher values than the experimental force constants. However, the trend in stretching force constants of a series of molecules is comparable with that of the corresponding experimental values.     

Zinc oxide nanowires in chemical bath on seeded substrates: Role of hexamine

Ceria-doped alumina sol-gel materials were obtained by two synthesis methods at low temperature; using method A, 2-propanol-diluted cerium precursor was slowly added at the time of the aluminum sol formation in acidic environment; using method B, the cerium salt was mixed with the aluminum alkoxide before sol formation in a basic environment. The supports were characterized by N₂ physisorption, thermogravimetric and thermal differential analyses (TGA and DTA), X-ray diffraction (XRD), ²⁷Al Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR), 2-propanol reactions, and ammonia temperature-programmed desorption (NH₃-TPD). The samples obtained by Method B present similar values in properties such as specific areas, pore volumes, pore size distribution, and acidity compared to those of pure alumina; the alumina structure was not modified, but segregated crystallites of CeO₂ were found in samples calcined at 1000 ^∘C, as observed by XRD. The ceria-containing materials synthesized by method A show a thermal behavior similar to that of alumina, with no appreciable segregation of CeO₂ detected by XRD and modifications in the amounts of tetra, penta, and octa-hedral aluminum coordination as determined by NMR. 2-propanol reactions showed a good correlation with acid density determined by NH₃-TPD. As the percentage of ceria in the material increases, surface area, pore volume, and acidity decrease. These changes can be correlated with an increase of pentacoordinated aluminum content. The results indicate that CeO₂ is well dispersed in the alumina framework when method A is used, but synthesis method B does not have the same effect on the CeO₂incorporation.     

Design-of-experiment optimization of exhaled breath condensate analysis using a miniature differential mobility spectrometer (DMS)

Analytical instruments that can measure small amounts of chemicals in complicated biological samples are often useful as diagnostic tools. However, it can be challenging to optimize these sensors using actual clinical samples, given the heterogeneous background and composition of the test materials. Here we use gas chromatography-differential mobility spectrometry (GC/DMS) to analyze the chemical content of human exhaled breath condensate (EBC). Ultimately, this system can be used for non-invasive disease diagnostics. Many parameters can be adjusted within this instrument system, and we implemented a factorial design-of-experiments to systematically test several combinations of parameter settings while concurrently analyzing effects and interactions.We examined four parameters that affect sensitivity and detection for our instrument, requiring a 2⁴ factorial design. We optimized sensor function using EBC samples spiked with acetone, a known clinical biomarker in breath. Two outputs were recorded for each experiment combination: number of chemicals detected, and the amplitude of acetone signal. Our goal is to find the best parameter combination that yields the highest acetone peak while also preserving the largest number of other chemical peaks in the spectra. By optimizing the system, we can conduct further clinical experiments with our sensor more efficiently and accurately.     

Time-dependent strength of colloidal gels

Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.     

Potential phytochemical inhibitors of SARS-CoV-2 helicase Nsp13: a molecular docking and dynamic simulation study

Molecular Diversity - The SARS-CoV-2 helicase Nsp13 is a promising target for developing anti-COVID drugs. In the present study, we have identified potential natural product inhibitors of...     

A novel catalyst-free mechanochemical protocol for the synthesis of 2,3-dihydro-1H-perimidines

A rapid, efficient, and green grinding assisted method for the synthesis of 2,3-dihydro-1H-perimidines has been developed. 1,8-Diaminonaphthalene and aldehydes were ground using mortar and pestle for 5 minutes affording the product in moderate to excellent yields. The methodology minimises the use of conventional workup and column chromatographic techniques.     

Electrochemical deposition of germanium sulfide from room-temperature ionic liquids and subsequent Ag doping in an aqueous solution

A facile room-temperature electrochemical deposition process for germanium sulfide (GeS(x)) has been developed with the use of an ionic liquid as an electrolyte. The electrodeposition mechanism follows the induced codeposition of Ge and S precursors in ionic liquids generating GeS(x) films. The electrodeposited GeS(x) films were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and Raman and X-ray photoelectron spectroscopy (XPS). An aqueous-based Ag doping method was used to dope electrochemically grown GeS(x) films with controlled doping compared to the conventional process, which can be used in next-generation solid-state memory devices.