Biobased epoxy/carbon fiber composites: Effect on mechanical,thermo-mechanical and morphological properties

Biobased epoxy was synthesized from diglycidyl ether of bisphenol A (DGEBA) and epoxidized castor oil (ECO) at a ratio of 80:20. Carbon fiber (CF) was used as a reinforcing agent to fabricate composites using biobased epoxy as matrix. Mechanical, Thermal and morphological properties of neat epoxy and biobased epoxy composites were investigated. Mechanical test results revealed that the composites prepared using five plies were higher than those with three plies and one ply respectively. This phenomenon revealed the effective reinforcing effect of carbon fiber due to its higher strength and higher crosslinking density. The composites also demonstrate high damping behavior as compared with neat epoxy and biobased epoxy blend. With increasing number of plies the composites thermal properties also shows an improvement. The SEM micrographs of the composites depicted that the biobased epoxy was fully adhered to the carbon fiber, thus representing a strong interface between CF/epoxy matrix.     

Toward resistance‐compromised DHFR inhibitors part 1: Combined structure/ligand‐based virtual screenings and ADME‐Tox profiling

The front‐line antimalarial drugs, for example, chloroquine, mefloquine, sulfadoxine, pyrimethamine, atovaquone, and artemether, are often failing because of the worldwide spread of drug‐resistant parasites. There has been significant recent interest in virtual screening to drive innovative drug discovery and to combat resistance efforts for a wide range of diseases. In fact, virtual screening has become the “gold standard” for major pharmaceutical industries and some university groups. Therefore, we present herein a structure‐based LibDock/CHARMM modeling and a set of appropriate scoring function evaluation criteria: correlation, consensus score, correlation‐based score, generally applicable replacement for root‐mean‐square deviation using a training set of 38 phenylthiazolyl‐1,3,5‐triazines from our previous reports and followed by a ligand‐based model to identify molecular features like hydrogen‐bond acceptor, hydrogen‐bond donor, hydrophobicity, and ring aromatic (RA) using Catalyst HipHop/HypoGen module. Next, TOPKAT module was applied to predict ADME‐Tox properties. The combined structure/ligand‐based approaches inadvertently arrived at a conserved Arg122 binding site from reliable LigScore1_dreiding top scoring function and are subsequently attributed to reserve important interactions and combat mutational drug resistance. The best pharmacophore model suggested that 1 hydrogen‐bond acceptor, 2 hydrophobicities, and 1 ring aromatic feature with good sensitivity at 0.50, specificity at 0.66, enrichment at 1.60, and accuracy at 0.50. Finally, good pharmacokinetics, metabolic stability, and toxicity endpoints were predicted in the comparison of proguanil and cycloguanil. These druggability insights are useful for researchers to deliver more effective, safer, both wild‐type and resistance‐compromised, and more economical dihydrofolate reductase inhibitors in the near future.     

Stability of small Pdn (n=1-7) clusters on the basis of structural and electronic properties: a density functional approach

Density functional calculations within the generalized gradient approximation have been used to investigate the lowest energy electronic and geometric structures of neutral, cationic, and anionic Pd(n) (n=1-7) clusters in the gas phase. In this study, we have examined three different spin multiplicities (M=1, 3, and 5) for different possible structural isomers of each neutral cluster. The calculated lowest energy structures of the neutral clusters are found to have multiplicities, M=1 for Pd(1), Pd(3), Pd(5), Pd(6), and Pd(7), while M=3 for Pd(2) and Pd(4). We have also determined the lowest energy states of cationic and anionic Pd(n) (n=1-7) clusters, formed from the most stable neutral clusters, in three spin multiplicities (M=2, 4, and 6). Bond length, coordination number, binding energy, fragmentation energy, bond dissociation energy, ionization potential, electron affinity, chemical hardness, and electric dipole moment of the optimized clusters are compared with experimental and other theoretical results available in the literature. Based on these criteria, we predict the four-atom palladium cluster to be a magic-number cluster.     

Fine-tuning of a ferrocene[porphyrin]ITO redox cascade for efficient sequential electron transfer commenced by an S2 photoexcited special-pair mimic

A systematic series of ferrocene/porphyrin redox cascade architectures was assembled through a slipped-cofacial porphyrin dimer on ITO electrode in optimizing the anodic photocurrent generation to perform the highest quantum yield compared to reported values on ITO electrodes.     

Synthesis of Novel Drug‐Like Small Molecules Based on Quinoxaline Containing Amino Substitution at C‐2

A series of novel “drug‐like” small molecules based on quinoxaline containing amino substitution at C‐2 were synthesized. All these molecules were prepared either via the reaction of 2‐phenyl‐3‐(piperazin‐1‐yl)quinoxaline with acyl bromides or benzyl bromides or various carboxylic acids or via the reaction of 2‐chloro‐3‐phenylquinoxaline with various amines. The structures of these novel compounds were confirmed by spectral analysis. The strategy used is simple and efficient and afforded good yields of quinoxaline derivatives.     

MD simulations and QM/MM calculations reveal the key mechanistic elements which are responsible for the efficient C–H amination reaction performed by a bioengineered P450 enzyme

An enzyme which is capable of catalyzing C–H amination reactions is considered to be a dream tool for chemists due to its pharmaceutical potential and greener approach. Recently, the Arnold group achieved this feat using an engineered CYP411 enzyme, which further undergoes a random directed evolution which increases its efficiency and selectivity. The present study provides mechanistic insight and the root cause of the success of these mutations to enhance the reactivity and selectivity of the mutant enzyme. This is achieved by means of comprehensive MD simulations and hybrid QM/MM calculations. The study shows that the efficient C–H amination by the engineered CYP411 is a combined outcome of electronic and steric effects. The mutation of the axial cysteine ligand to serine relays electron density to the Fe ion in the heme, and thereby enhances the bonding capability of the heme-iron to the nitrogen atom of the tosyl azide. In comparison, the native cysteine-ligated P450 cannot bind the tosyl azide. Additionally, the A78V and A82L mutations in P411 provide ‘bulk’ to the active site which increases the enantioselectivity via a steric effect. At the same time, the QM/MM calculations elucidate the C–H amination by the iron nitrenoid, revealing a mechanism analogous to Compound I in the native C–H hydroxylation by P450.

Computer simulation method reveals the mechanism of C–H amination reaction due to a single site mutation.     

Synthesis of functionalized Cu:ZnS nanosystems and its antibacterial potential

Copper doped Zinc Sulfide (Cu:ZnS) nanoparticles were synthesized as potential antibacterial agents, through a solvothermal approach using Mercaptosuccinic acid (MSA) and Sodium citrate (SC) as differential capping agents. Multiple variants of the Cu:ZnS nanoparticles were generated based on the refluxing intervals of the reactions and a choice of the capping agents. The microstructural properties and the elemental composition of the synthesized nanosystems were examined using Scanning Electron Microscopy (SEM) and powder X-ray Diffraction (XRD), along with Energy-Dispersive X-ray spectroscopy (EDX) and Microwave Plasma-Atomic Emission Spectroscopy (MP-AES). The as-synthesized nanosystems were also characterized for their surface attributes using Fourier Transform Infrared spectroscopy (FT-IR), while the optical properties were studied using UV–Vis spectroscopy. The electrostatic stability of the aqueous dispersions of Cu:ZnS was studied as a function of their solvent pH, using Photon Correlation Spectroscopy. For the assessment of the antibacterial properties of the different variants of Cu:ZnS nanosystems, the disk diffusion assay was performed against both Gram-positive and Gram-negative bacteria. The results show a promising antibacterial activity for the Cu:ZnS variants synthesized, with a prominent activity in the [email protected]:ZnS nanoparticle making them a novel class of potential antibacterial agents.     

An efficient ψ-v scheme for two-dimensional laminar flow past bluff bodies on compact nonuniform grids

We recently proposed a second-order accurate ψ-v formulation of the steady-state Navier-Stokes (N-S) equations on compact Cartesian nonuniform grids. In the current work, we extend the ideas of the aforesaid formulation and propose a second-order spatially compact, implicit, stable ψ-v formulation for the unsteady incompressible N-S equations. Contrary to the existing ψ-v finite difference formulations which use grid transformation, the proposed scheme is developed for nonuniform Cartesian grids without transformation specifically designed for two-dimensional laminar flow past bluff bodies. It has been implemented on problems of internal flows inside curved regions as well as those involving fluid-embedded body interaction. However, the robustness of the scheme is highlighted by the accurate resolution of a host of complex flows past bluff bodies with different physical set-ups and boundary conditions. It was seen to handle problems involving both uniform and accelerated flows across a wide range of structures of varied shape, namely, a flat plate, a circular cylinder, inclined square cylinder, and a wedge in channel hinged to the wall. Apart from elegantly capturing all the details of the shedded vortex structures under different circumstances, the scheme was also able to handle both Dirichlet and Neumann boundary with equal ease. In all the cases, our results are found to be extremely close to the available numerical and experimental results.     

Eighth power moment of Kloosterman sum,supercharacters, and elliptic curves

The Ramanujan Journal - We here use a supercharacter theory of $${\mathbb {F}}_p^2$$ to express the eighth power moment of Kloosterman sum in terms of traces of Frobenius endomorphism of certain...