Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of d- and l-aspartic acid

A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of l-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the l-aspartic acid imprinted modified electrode showed a wide linear response for l-aspartic acid within the concentration range 9.98–532.72 ng mL^? 1, with the minimum detection limit of 1.73–1.79 ng mL^? 1 (S/N = 3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL^? 1) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of l-aspartic acid biomarker, in clinical settings.     

Mechanism of Blood–Heart-Barrier Leakage: Implications for COVID-19 Induced Cardiovascular Injury

Although blood–heart-barrier (BHB) leakage is the hallmark of congestive (cardio-pulmonary) heart failure (CHF), the primary cause of death in elderly, and during viral myocarditis resulting from the novel coronavirus variants such as the severe acute respiratory syndrome novel corona virus 2 (SARS-CoV-2) known as COVID-19, the mechanism is unclear. The goal of this project is to determine the mechanism of the BHB in CHF. Endocardial endothelium (EE) is the BHB against leakage of blood from endocardium to the interstitium; however, this BHB is broken during CHF. Previous studies from our laboratory, and others have shown a robust activation of matrix metalloproteinase-9 (MMP-9) during CHF. MMP-9 degrades the connexins leading to EE dysfunction. We demonstrated juxtacrine coupling of EE with myocyte and mitochondria (Mito) but how it works still remains at large. To test whether activation of MMP-9 causes EE barrier dysfunction, we hypothesized that if that were the case then treatment with hydroxychloroquine (HCQ) could, in fact, inhibit MMP-9, and thus preserve the EE barrier/juxtacrine signaling, and synchronous endothelial-myocyte coupling. To determine this, CHF was created by aorta-vena cava fistula (AVF) employing the mouse as a model system. The sham, and AVF mice were treated with HCQ. Cardiac hypertrophy, tissue remodeling-induced mitochondrial-myocyte, and endothelial-myocyte contractions were measured. Microvascular leakage was measured using FITC-albumin conjugate. The cardiac function was measured by echocardiography (Echo). Results suggest that MMP-9 activation, endocardial endothelial leakage, endothelial-myocyte (E-M) uncoupling, dyssynchronous mitochondrial fusion-fission (Mfn2/Drp1 ratio), and mito-myocyte uncoupling in the AVF heart failure were found to be rampant; however, treatment with HCQ successfully mitigated some of the deleterious cardiac alterations during CHF. The findings have direct relevance to the gamut of cardiac manifestations, and the resultant phenotypes arising from the ongoing complications of COVID-19 in human subjects.     

Variation and recovery of resistivity of industrial greases — an experimental investigation

In the present work, variation in the resistivity of different greases with time in static conditions, under the influence of applied potential drops, is established. The change in resistivity and physico-chemical characteristics of the greases in electric fields, and recovery of the resistivity within the test period in the absence of applied potential drop, have been found. The properties of the greases are compared, and their correlation with resistivity is analysed. The paper also gives the results of analysis using an SRV tester, IR spectra, chemical analysis and spectrophotometry, of changes that occurred periodically in the greases, normally used in non-insulated rolling-element bearings in the presence of a potential drop across the inner and outer races. The paper highlights the behaviour and mechanism of the process of bearing failure under electric fields.     

Relative comparison of stiffness and damping properties of double decker high precision and conventional rolling-element bearings

This paper reports the relative comparison of stiffness and damping properties of Double Decker High Precision Bearing (DDHPB) and conventional rolling-element bearings. It has been determined that under different load and speed conditions, DDHPB and the conventional bearings have identical critical speed, comparable net deflection and stiffness. On the contrary, relative damping of the DDHPB, evaluated by rotating speed component of vibrations, at different operating conditions is approximately three times more than that of the conventional bearing. Excitation tests at different speeds have also indicated better damping characteristics of DDHPB as compared to the conventional bearing. This potential of DDHPB permits its use in typical industrial applications where damping is a significant requirement.     

Sol–gel derived multiwalled carbon nanotubes ceramic electrode modified with molecularly imprinted polymer for ultra trace sensing of dopamine in real samples

A new class of composite electrodes made of sol–gel derived ceramic-multiwalled carbon nanotubes is used for the growth of a nanometer thin film adopting “surface grafting-from approach”. For this the multiwalled carbon nanotubes-ceramic electrode surface is first modified with an iniferter (benzyl N,N-diethyldithiocarbamate) and then dopamine imprinted polymer, under UV irradiation, for differential pulse anodic stripping voltammetric sensing of dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples (detection limit 0.143–0.154 ng mL⁻¹, 3σ), without any cross reactivity, interferences and false-positive contributions. Such composite electrodes offer higher stability, electron kinetics, and renewable porous surface of larger electroactive area (with insignificant capacitance) than carbon ceramic electrodes. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of dopamine.     

A General Approach to the Synthesis of β2‐Amino Acid Derivatives via Highly Efficient Catalytic Asymmetric Hydrogenation of α‐Aminomethylacrylates

A new strategy was developed for the synthesis of a valuable class of α‐aminomethylacrylates via the Baylis–Hillman reaction of different aldehydes with methyl acrylate followed by acetylation of the resulting allylic alcohols and S_N2′‐type amination of the allylic acetates. Asymmetric hydrogenation of these diverse olefinic precursors using rhodium(Et‐Duphos) catalysts provided the corresponding β²‐amino acid derivatives with excellent enantioselectivities and exceedingly high reactivities (up to >99.5% ee and S/C=10,000). The first hydrogenation of (Z)‐configurated substrates was studied for the synthesis of β²‐amino acid derivatives. The high influence of the substrate geometry and steric hindrance on the reactivity and enantioselectivity was also disclosed for this reaction. This protocol provides a highly practical, facile and scalable method for the preparation of optically pure β²‐amino acids and their derivatives under mild reaction conditions.     

Data science assisted cohesive finite element modelling of impact behaviour of AP-HTPB crystal binder composite

In this work, the response of an ammonium perchlorate (AP)-hydroxyl-terminated polybutadiene (HTPB) composite material under impact loading is presented, utilizing computational cohesive finite element method (CFEM) simulations that are validated with drop hammer experiments. This study examined the impact behaviour of AP crystal sizes between 200 and 400 μm by varying impact velocities between 3 and 10 m/s. Based on the outcome of CFEM simulations, analysis of variance (ANOVA) tests and a response surface method (RSM) were utilized to construct a mathematical model approximating the relationships between simulation inputs and outcomes. Both computational and experimental results show that the local strain rate has a considerable positive correlation with crystal size, and the rate of temperature change has positive correlations with both crystal size and impact velocity. Further, it was observed that stiffness and compression energy are the primary factors to variances in local strain rate and rate of change of temperature. RSM has been found to be an effective tool for modelling impact responses of materials under varying experimental conditions.