Bifunctionalized Intrinsically Microporous Polyimides with Simultaneously Enhanced Gas Permeability and Selectivity

Two novel intrinsically microporous copolyimides synthesized by condensation reaction of 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3,3′,3′‐tetramethyl‐1,1′‐spirobisindane‐5,5′‐diamino‐6,6′‐diol, and 3,5‐diaminobenzoic acid with diamine ratios of 80/20 (Co‐80/20) and 50/50 (Co‐50/50) are reported. Unexpectedly, the Co‐80/20 not only demonstrates higher microporosity (300 m² g⁻¹) than the PIM‐6FDA‐OH homopolymer (190 m² g⁻¹) but also exhibits simultaneously enhanced CO₂ permeability (from 119 to 171 Barrer) and CO₂/CH₄ selectivity (from 35 to 41) after thermal annealing at 250 °C. This higher permeability originates from enhanced diffusivity (D _CO2) and the higher selectivity results from its increased diffusion selectivity (D _CO2/D _CH4). After crosslinking at 300 °C, the Co‐80/20 exhibits an even higher CO₂ permeability (261 Barrer) and almost unchanged CO₂/CH₄ selectivity.

     

Oxygen migration in A2B2O7 pyrochlores

Atomic scale computer simulation has been used to predict activation energies for oxygen migration. In total, 54 compounds with the A₂B₂O₇ pyrochlore structure were simulated. In each case, oxygen migration was assumed to proceed via an oxygen vacancy mechanism with oxygen ions hopping between 48f sites. For some compounds the unoccupied 8a interstitial position played an important role in the migration mechanism. The results were analyzed using a contour map of activation energy versus A cation radius along the ordinate and B cation radius along the abscissa. This identified areas of similar cation radii, which exhibit lower activation energy. Results compare favourably with available experimental data.     

Corrosion Inhibition of Mild Steel in Hydrochloric Acid Environment Using Terephthaldehyde Based on Schiff Base: Gravimetric,Thermodynamic, and Computational Studies

Using traditional weight-loss tests, as well as different electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy), we investigated the corrosion-inhibition performance of 2,2′-(1,4-phenylenebis(methanylylidene)) bis(N-(3-methoxyphenyl) hydrazinecarbothioamide) (PMBMH) as an inhibitor for mild steel in a 1 M hydrochloric acid solution. The maximum protection efficacy of 0.0005 M of PMBMH was 95%. Due to the creation of a protective adsorption layer instead of the adsorbed H₂O molecules and acidic chloride ions, the existence of the investigated inhibitor reduced the corrosion rate and increased the inhibitory efficacy. The inhibition efficiency increased as the inhibitor concentration increased, but it decreased as the temperature increased. The PMBMH adsorption mode followed the Langmuir adsorption isotherm, with high adsorption-inhibition activity. Furthermore, the value of the ∆Gadso indicated that PMBMH contributed to the physical and chemical adsorption onto the mild-steel surface. Moreover, density functional theory (DFT) helped in the calculation of the quantum chemical parameters for finding the correlation between the inhibition activity and the molecular structure. The experimental and theoretical findings in this investigation are in good agreement.     

Structural and Electronic (Absorption and Fluorescence) Properties of a Stable Triplet Diphenylcarbene: A DFT Study

A triplet diphenylcarbene, bis[3-bromo-5-(trifluoromethyl)[1,1'-biphenyl]-4-yl]methylidene (B3B), with exceptional stability was discovered by chemists from Japan's Mie University. To investigate its different quantum chemical features, a theoretical analysis was predicated on Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) based technique. According to the findings, the singlet–triplet energy gap (ES-T), as well as HOMO–LUMO energy bandgap (E_H-L), was found to be diminished when nucleophilicity (N) rose. We looked at the geometrical dimensions, molecular orbitals (MOs), electronic spectra, electrostatic potential, molecular surfaces, reactivity characteristics, and thermodynamics features of the title carbene (B3B). Its electronic spectra in different solvents were calculated using TD-DFT and Polarizable Continuum Model (PCM) framework. The estimated absorption maxima of B3B were seen between 327 and 340 nm, relying on the solvents, and were attributed to the S⁰?→?S¹ transition. Estimated fluorescence spectral peaks were found around 389 and 407 nm with the S¹ and S⁰ transitions being identified. Its fluorescence/absorption intensities revealed a blue shift change when the solvent polarity was increased. The least exciting state has been discovered to be the π?→?π^* charge-transfer (CT) phase. According to the Natural Bonding Orbital (NBO) exploration, ICT offers a significant role in chemical system destabilization. Furthermore, several hybrid features were used to determine the NLO (nonlinear optical) features (polarizability, first-order hyperpolarizability, and dipole moment). The calculated values suggest that B3B is a promising candidate for further research into nonlinear optical properties.

Graphical Abstract

     

Preparation and Optimization of PEGylated Nano Graphene Oxide-Based Delivery System for Drugs with Different Molecular Structures Using Design of Experiment (DoE)

Graphene oxide (GO), due to its 2D planar structure and favorable physical and chemical properties, has been used in different fields including drug delivery. This study aimed to investigate the impact of different process parameters on the average size of drug-loaded PEGylated nano graphene oxide (NGO-PEG) particles using design of experiment (DoE) and the loading of drugs with different molecular structures on an NGO-PEG-based delivery system. GO was prepared from graphite, processed using a sonication method, and functionalized using PEG 6000. Acetaminophen (AMP), diclofenac (DIC), and methotrexate (MTX) were loaded onto NGO-PEG particles. Drug-loaded NGO-PEG was then characterized using dynamic light scattering (DLS), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), XRD. The DLS data showed that the drug-loaded NGO-PEG suspensions were in the size range of 200 nm–1.3 µm. The sonication time and the stirring rate were found to be the major process parameters which affected the average size of the drug-loaded NGO-PEG. FTIR, DSC, XRD, and SEM demonstrated that the functionalization or coating of the NGO occurred through physical interaction using PEG 6000. Methotrexate (MTX), with the highest number of aromatic rings, showed the highest loading efficiency of 95.6% compared to drugs with fewer aromatic rings (diclofenac (DIC) 70.5% and acetaminophen (AMP) 65.5%). This study suggests that GO-based nano delivery systems can be used to deliver drugs with multiple aromatic rings with a low water solubility and targeted delivery (e.g., cancer).     

Correction to: Pore Space and Fluid Phase Characterization in Round and Angular Partially Saturated Sands Using Radiation‑Based Tomography and Persistent Homology

Transport in Porous Media - A correction to this paper has been published: https://doi.org/10.1007/s11242-021-01630-1     

Dynamical analysis of coronavirus disease with crowding effect,and vaccination: a study of third strain

Nonlinear Dynamics - Countries affected by the coronavirus epidemic have reported many infected cases and deaths based on world health statistics. The crowding factor, which we named "crowding...     

Bilateral filtering with adaptation to phase coherence and noise

In this paper, a bilateral filter with adaptive domain and range parameter is introduced for image denoising. Since the objective of denoising is to reduce noise as much as possible while preserving the perceptually important details, the parameters are adjusted in accordance with perceptual significance of pixels and noise level. The domain parameter is obtained by using the maximum and minimum moments of local phase coherence for being the representative of image details such as edges and corners of an image. The range parameter is estimated from the intensity-homogeneity measurements for their ability to represent the underlying noise. In addition, the filter is applied in an iterative manner to reduce the residual noise. Experiments are carried out using various standard images, and the results show that the proposed method is more effective in reducing additive white Gaussian noise as compared to several recently introduced denoising techniques in terms of the peak signal-to-noise ratio, structural similarity index and visual quality. In addition, experiments performed using real noisy images reveal the ability of the proposed filter to provide denoised images of better visual quality.     

On a new class of probability distributions

Multicomponent systems are widely used in computer science. The reliability of these systems plays a very important role in efficient working. These systems are not always supposed to follow the standard probability distributions and so pseudo-distributions can be thought of as suitable alternatives. In this work we have defined a new bivariate pseudo-Weibull distribution. Some standard properties of the distribution have been studied. The distributions of the order statistics and concomitants have also been obtained.