Nanostructure Engineering of Metal–Organic Derived Frameworks: Cobalt Phosphide Embedded in Carbon Nanotubes as an Efficient ORR Catalyst

Heteroatom doping is considered an efficient strategy when tuning the electronic and structural modulation of catalysts to achieve improved performance towards renewable energy applications. Herein, we synthesized a series of carbon-based hierarchical nanostructures through the controlled pyrolysis of Co-MOF (metal organic framework) precursors followed by in situ phosphidation. Two kinds of catalysts were prepared: metal nanoparticles embedded in carbon nanotubes, and metal nanoparticles dispersed on the carbon surface. The results proved that the metal nanoparticles embedded in carbon nanotubes exhibit enhanced ORR electrocatalytic performance, owed to the enriched catalytic sites and the mass transfer facilitating channels provided by the hierarchical porous structure of the carbon nanotubes. Furthermore, the phosphidation of the metal nanoparticles embedded in carbon nanotubes (P-Co-CNTs) increases the surface area and porosity, resulting in faster electron transfer, greater conductivity, and lower charge transfer resistance towards ORR pathways. The P-Co-CNT catalyst shows a half-wave potential of 0.887 V, a Tafel slope of 67 mV dec⁻¹, and robust stability, which are comparatively better than the precious metal catalyst (Pt/C). Conclusively, this study delivers a novel path for designing multiple crystal phases with improved catalytic performance for energy devices.     

Synthesis,Characterization and Structural Conformation Studies of 2-Amino-3-ethoxycarbonyl-4-(4′-methoxy Phenyl)-4H-pyrano-[3,2-c]-chromene-6-methyl-5-one

2-amino-3-ethoxycarbonyl-4-(4′-methoxy Phenyl)-4H-pyrano-[3,2-c]-chromene-6-methyl-5-one was synthesized by the two-component reaction of 6-methyl-4-hydroxy coumarin with 4′-methoxy-2-cyano cinnamate, which was synthesized by Knoevenagel reaction with 88% yield. The compound obtained was characterized by spectroscopic techniques and confirmed by X-ray crystallographic studies. The crystallographic data analysis reveals that the title compound crystallizes in the triclinic space group \(P\overline{1}\) with cell parameters a = 7.7750(8) Å, b = 9.0310(6) Å, c = 15.6120(17) Å, α = 77.249(7)°, β = 115.860(3)°, γ = 70.139(7)°, V = 1,003.0(16) Å³ for Z = 4. The structure has been solved by direct methods and refined to R1 = 0.0552 for 3,164 observed reflections with I > 2 σ(I). The pyran ring is in a flattened boat conformation. The carbonyl group is oriented in a -synperiplanar(cis) conformation.

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Preparation and dielectric study of high-quality PLZT x/65/35 (x = 6,7,8) ferroelectric ceramics

Ferroelectric ceramics are an important class of solid-state materials as they exhibit a wide range of applications. Various compositions of the ferroelectric ceramic (Pb,La)(Zr,Ti)O₃ (known as PLZT) were prepared and their dielectric properties were studied. It is difficult to prepare phase-pure PLZT compounds by the direct solid-state reaction method. Its preparation required the use of a special 'covering method' adopted to facilitate phase formation using the solid-state reaction method. High-quality PLZT samples of different compositions (x/65/35, x=6,7,8) prepared using the 'covering method' without adding any excess PbO (to avoid PbO loss) resulted in single-phase formation. The 8/65/35 composition has yielded a dielectric constant of 11273 at T_C, which is in good agreement with the literature value [1, 2]. Also, as the lanthanum content x was varied from 6 to 8 mole %, T_C decreased and the low-frequency (1 kHz) room-temperature dielectric constant value increased. The present publication gives a detailed account of the evolution of the phase-pure PLZT compositions and their physical properties.     

Solubilization of Cationic Hemicyanine Dyesin Anionic Surfactant Micelles: A Partitioning Study

Summary.  Cationic hemicyanine dyes of the 1-methyl-4-(4-(di-n-alkylamino)-styryl) pyridinium betain type (alkyl group=methyl to butyl) have been investigated by differential spectroscopy in order to ascertain their solubilization in aqueous micellar solution of sodium dodecylbenzene sulfonate (SDBS). The differential absorption spectra were recorded as a function of surfactant concentration at 25.0°C. Thermodynamic parameters were calculated from partition coefficient data. The results show that cationic hemicyanine dyes are solubilized at the micellar surface, indicating an electrostatic interaction between dyes and surfactant micelles. Received October 15, 1999. Accepted February 14, 2000     

Synthesis and structural conformation of N‐substituted 1,4‐dihyropyridine derivatives

N‐(Phenyl)‐3,5‐dicarbethoxy‐2,6‐dimethyl‐4‐(phenyl)‐1,4‐dihydropyridine (A) and N‐(4‐methoxy phenyl)‐‐3,5 dicarbethoxy‐2,6 dimethyl‐4‐(3‐nitro phenyl)‐1,4‐dihydropyridine (B) has been synthesized as per scheme and characterized by the X‐ray diffraction method. The compound A crystallizes in monoclinic space group P21/c with cell parameters a = 9.2770(11)Å, b = 8.6410(5)Å, c = 27.601(3)Å, β = 97.724(3)°, Z = 4. The compound B crystallizes in monoclinic space group P21/c with cell parameters a = 11.229(6), b = 12.746(7)Å, c =17.606(6)Å, β = 104.531(3)°, Z = 4. The structures exhibit both intra and intermolecular hydrogen bonds. Dihydropyridine ring of both the compounds adopt a flat boat conformation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vocal Fold Impact Stress Analysis

Vocal fold impact stress (force/area) has been implicated as a factor possibly contributing to the formation of nodules and polyps. The force of impact of a moving body is related to its acceleration. Since the mass of the folds is relatively constant, one expects impact force to be directly proportional to acceleration. A measure that reflects the relative displacement of the vocal folds is photoglottography (PGG). The velocity and acceleration of the folds are easily obtained by calculating the first and second derivatives of the PGG displacement waveform. This study, therefore, compared the second derivative of the PGG signal with simultaneously measured impact stress in an excised canine larynx model. Glottal transillumination (PGG) was measured with a subglottic transducer. A miniature force transducer placed in the midline between the vocal folds measured impact stress at the midglottal position. For nine different larynges, there was a positive and linear relationship between the second derivative of PGG and impact stress. The statistically significant results support the hypothesis that the second derivative of PGG m ay provide a use fulnoninvasive way to estimate relative vocal fold impact stress.     

Stannous(II) trifluoromethane sulfonate: a versatile catalyst for the controlled ring‐opening polymerization of lactides: Formation of stereoregular surfaces from polylactide “brushes”

A general method for the controlled synthesis of polylactide in solution and from solid supports is presented. The evaluation of stannous(II) trifluoromethane sulfonate [Sn(OTf)₂] and scandium(III) trifluoromethane sulfonate [Sc(OTf)₃] as catalysts for the ring‐opening polymerization (ROP) of L ‐, D ‐, and L ,D ‐lactide is described as a route to polylactide using mild and highly selective conditions. These triflate catalysts must be used in conjunction with a nucleophilic compound such as an alcohol that is the actual initiating species via the active metal alkoxide species. Consistent with this process, ¹H NMR analysis revealed that the α‐chain‐end bears the ester from the initiating alcohol, and upon hydrolysis of the active metal alkoxide chain end, a ω‐hydroxyl chain end was clearly detected. Polymers of predictable molecular weights and narrow polydispersities were obtained in high yields in accordance with a controlled polymerization process. The addition of base either as a solvent or additive significantly enhanced the polymerization rate with minimal loss to the polymerization control. The ROP of lactide isomers from an initiator, HO(CH₂CH₂O)₃(CH₂)₁₁SH, self‐assembled onto a gold surface using Sn(OTf)₂ produced polylactide brushes under living conditions and provides the opportunity to prepare stereoregular or chiral surfaces by polymerization of enantiomerically pure monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3529–3538, 2001     

Computational Study of SARS-CoV-2 RNA Dependent RNA Polymerase Allosteric Site Inhibition

The COVID-19 pandemic has caused millions of fatalities since 2019. Despite the availability of vaccines for this disease, new strains are causing rapid ailment and are a continuous threat to vaccine efficacy. Here, molecular docking and simulations identify strong inhibitors of the allosteric site of the SARS-CoV-2 virus RNA dependent RNA polymerase (RdRp). More than one hundred different flavonoids were docked with the SARS-CoV-2 RdRp allosteric site through computational screening. The three top hits were Naringoside, Myricetin and Aureusidin 4,6-diglucoside. Simulation analyses confirmed that they are in constant contact during the simulation time course and have strong association with the enzyme’s allosteric site. Absorption, distribution, metabolism, excretion and toxicity (ADMET) data provided medicinal information of these top three hits. They had good human intestinal absorption (HIA) concentrations and were non-toxic. Due to high mutation rates in the active sites of the viral enzyme, these new allosteric site inhibitors offer opportunities to drug SARS-CoV-2 RdRp. These results provide new information for the design of novel allosteric inhibitors against SARS-CoV-2 RdRp.     

Correction to: Identifying Efficient Transport Pathways in Early‑Wood Timber: Insights from 3D X‑ray CT Imaging of Softwood in the Presence of Flow

Transport in Porous Media - A correction to this paper has been published: https://doi.org/10.1007/s11242-021-01569-3