Tribological Behavior of Ultrananocrystalline Diamond (UNCD) Thin Films by Varying their Growth Conditions

The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And National Symposium On Advances In Functional And Exotic Materials.</p

sj-docx-1-pie-10.1177_09544089231218118 - Supplemental material for Improvement in tribological and hydrophobic properties of thrust plate of gear pump through oxyacetylene flame spraying in diverse cooling Medium

Supplemental material, sj-docx-1-pie-10.1177_09544089231218118 for Improvement in tribological and hydrophobic properties of thrust plate of gear pump through oxyacetylene flame spraying in diverse cooling Medium by Anubhav K Sharma, Niranjan Kumar and Alok K Das in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p

Structure-based virtual screening, molecular dynamics simulation and MM-PBSA toward identifying the inhibitors for two-component regulatory system protein NarL of <i>Mycobacterium Tuberculosis</i>

The nitrate/nitrite response regulatory protein NarL belongs to the two-component regulatory system of Mycobacterium tuberculosis (MTB), plays a crucial role in anaerobic survival of mycobacteria in host. The absence of this protein in humans, makes it an attractive drug target for MTB treatment. However, the specific drug molecules targeting NarL are yet to be identified. In this study, we identified the promising drug candidates using structure based virtual screening of compounds from chemical libraries (ChEMBL and ZINC), followed by the extensive physicochemical properties analyses and molecular dynamics (MD) simulation. As the initial results, we obtained 4,754 bioactive compounds from ChEMBL having anti-tuberculosis activity which is finally narrowed down to the best 10 hits. A similar approach was applied to search for structurally similar compounds from ZINC data, corresponding to the top hits obtained from ChEMBL. Our collective results show that two compounds, ChEMBL509609 (Gscore – 5.054 kcal/mol, Xscore – 6.47 kcal/mol) and ZINC01843143 (Gscore – 5.114 kcal/mol, Xscore – 6.46 kcal/mol) having the best docking score and ADMET profile. The structural stability and dynamics of lead molecules at active site of NarL were examined using MD simulation and the binding free energies were estimated with MM-PBSA. Essential dynamics and MM-PBSA demonstrated that NarL-ChEMBL509609 complex remains the most stable during simulation of 100 ns with the higher binding free energy which may be a suitable candidate for further experimental analysis. AbbreviationsADMEAbsorption, Distribution, Metabolism, And ExcretionBCGBacillus Calmette-GuerinCNSCentral nervous systemDOTSDirectly observed treatment, short courseEDEssential dynamicsHIVHuman immunodeficiency virusHKHistidine kinaseHOAHuman oral absorptionHTVSHigh throughput virtual screeningIRRIIrritationMDMolecular dynamicsMDRMultidrug resistantMTBMycobacterium tuberculosisMUTMutagenicityMWMolecular weightPHOAPercentage of human oral absorptionREPReproductive developmentRgRadius of gyrationRMSDRoot mean square deviationRMSFRoot mean square fluctuationRO5Lipinski’s rule of fiveRRResponse regulatorSPStandard precisionSPGStandard precision glideTBTuberculosisTCSTwo-component regulatory systemTDRTotally drug-resistantTUMOTumorigenicityWHOWorld health organizationXDRExtensively drug-resistantXPExtra precision Absorption, Distribution, Metabolism, And Excretion Bacillus Calmette-Guerin Central nervous system Directly observed treatment, short course Essential dynamics Human immunodeficiency virus Histidine kinase Human oral absorption High throughput virtual screening Irritation Molecular dynamics Multidrug resistant Mycobacterium tuberculosis Mutagenicity Molecular weight Percentage of human oral absorption Reproductive development Radius of gyration Root mean square deviation Root mean square fluctuation Lipinski’s rule of five Response regulator Standard precision Standard precision glide Tuberculosis Two-component regulatory system Totally drug-resistant Tumorigenicity World health organization Extensively drug-resistant Extra precision Communicated by Ramaswamy H. Sarma</p

Load Dependent Nanoindentation Studies of Ultrananocrystalline Diamond (UNCD) Thin Films

The talk presented at 29th Annual General Meeting Of Materials Research Society Of India And National Symposium On Advances In Functional And Exotic Materials.</p

Evaluation of tribological efficacy and EP lubricity properties of gear oil (EP90) energized with molybdenum disulfide (MoS₂) nano-additives

The practice of employing efficient lubricants involving functional additives has become imperative in order to enhance engine efficiency, to say the least. The span of an engine’s life can be greatly enhanced by gear oil’s tribological and thermo-physical properties. Addressing the tribological management of gearbox components within the mechanical sector is a dire necessity. In a quest for exceptional nanolubricants with improved serviceability, present manuscript deals with the dispersion of metallic-sulphide nano dispersants in gear oil lubricant. Nanolubricants were prepared by dispersing molybdenum disulfide nanoparticles (MoS2 Nps) in gear oil with varying concentrations of 0.1%, 0.3%, and 0.5% by volume (v/v). Then nanolubricants’ thermo-physical properties were assessed and contrasted with those of plain gear oil. This was followed by the measurement of the tribological and extreme pressure properties of the nanolubricant samples on a four-ball tester. According to the findings, as compared to gear oil, the prepared nanolubricant yielded a maximum reduction of 9.21% and 9.38% in coefficient of friction and an average wear scar diameter, respectively. A maximum augmentation of 12% in weld load was obtained with 0.3% nanolubricant sample. The wear scar on the steel balls was examined using field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscope (EDS). The investigations revealed the presence of ball bearing and surface polishing effects as dominant lubricating mechanisms, which potentially contribute to the enhanced tribological properties of the oil. Hence, adding MoS2 Nps in gear oil may solve many engineering problems related to the lubricity of the base oil.</p

Enhanced Lubricity of SnO₂ Nanoparticles Dispersed Polyolester Nanofluid

Nanofluid lubrication is a novel approach for enhancing energy efficiency of the sliding interfaces which is useful for reducing friction and wear of the machine elements. The SnO₂ nanoparticles (NPs) of 25 nm size and concentration 0.03 mg mL^–1 dispersed in polyolester (POE) oil is found to exhibit significant reduction in friction coefficient and wear up to 38 and 42%, respectively, in comparison to neat POE oil. It is also found that the lubrication efficiency depends on size of the NPs, dispersion stability, and concentration. Fourier transform infrared red spectroscopy confirmed that the chemical stability of the POE was preserved after the tribology test and there was no product due to oxidation reaction. Formation of low shear strength tribofilm containing organic compounds and SnO₂ nanoparticles was key factor in reduction of the friction and protection against wear and deformation

Effective Noncovalent Functionalization of Poly(ethylene glycol) to Reduced Graphene Oxide Nanosheets through γ‑Radiolysis for Enhanced Lubrication

High-quality reduced graphene oxide (rGO) nanosheets (NSs) were synthesized by the oxidation of graphite followed by hydrazine treatment for the reduction of the oxygen functionalities. γ-Radiolysis was then used for the functionalization of the rGO-NSs with poly­(ethylene glycol) 200 (PEG200). The functionalization resulted in the intercalation of PEG200 molecules in rGO through hydrogen bonding between the hydroxyl groups of rGO and the oxygen atoms of PEG200 molecules. This resulted in an increase in the <i>d</i> spacing of the graphene sheets and a decrease in the defect density of the carbon network in the rGO. The friction coefficient and wear of sliding steel surfaces were reduced by 38% and 55%, respectively, when 0.03 mg mL^–1 PEG200-functionalized rGO dispersed in PEG200 was used. The lubrication properties can be described by bipolar interactions between PEG200 and rGO, leading to effective dispersion. Chemical analysis of wear particles showed decomposition of rGO into nanosized graphite domains, as exhibited by mechanical energy produced in tribo-contact. Moreover, these domains formed effective and stable tribofilms on the steel wear tracks that easily sheared under the action of contact stress. This significantly enhanced the antifriction and antiwear properties, resulting in improved oxidation resistance of PEG200 under the tribo-contact. It was found that, at high rGO concentrations, the lubrication efficiency decreased as a result of graphene–graphene intersheet collisions, producing mechanical energy and chemical defects at contact interfaces

Tribological Properties of Ultrananocrystalline Diamond Films in Inert and Reactive Tribo-Atmospheres: XPS Depth-Resolved Chemical Analysis

Tribological properties of diamond films are sensitive to the chemically reactive and inert tribo-atmospheric media, and therefore, it is difficult to understand the underlying tribological mechanisms. In the present work, tribological properties of surface-modified ultrananocrystalline diamond (UNCD) thin films were investigated in four distinct tribo-environmental conditions of ambient humid-atmosphere, nitrogen (N₂), argon (Ar), and methane (CH₄) gases. The in situ depth-resolved X-ray photoelectron spectroscopy (XPS) showed the desorption of oxygen and oxy-functional additives and sputtering of weakly bonded amorphous carbon species from the UNCD film surface after the Ar⁺-ion sputtering process. After desorption of these chemical entities, friction and wear were decreased and run-in regime cycles became shorter in UNCD films. Friction in the ambient humid-atmosphere was higher compared to other tribo-environmental conditions, and it was explained by the oxidation mechanism of the sliding interfaces and the formation of the oxidized carbon transferfilm. However, low friction and wear in the N₂ atmosphere was associated with the adsorption of N₂ species, forming nitrogen-terminated carbon bonds at the sliding interfaces. This was directly investigated by XPS and energy dispersive X-ray spectroscopy techniques. Furthermore, low friction in the Ar atmosphere was explained by the physical adsorption of Ar gaseous species, which tend to avoid the covalent carbon bond formation across the sliding interfaces. Moreover, ultralow friction in the CH₄ atmosphere was governed by the passivation of dangling carbon bonds by dissociative CH₄ complexes, which creates hydrogen-terminated repulsive sliding interfaces. More importantly, a shorter run-in regime with low friction and wear in Ar⁺-ion-sputtered UNCD films were explained by desorption of the oxygen and oxy-functional groups, which are inherently present in the UNCD films

Data_Sheet_1_Identifying the Novel Inhibitors Against the Mycolic Acid Biosynthesis Pathway Target “mtFabH” of Mycobacterium tuberculosis.docx

Mycolic acids are the key constituents of mycobacterial cell wall, which protect the bacteria from antibiotic susceptibility, helping to subvert and escape from the host immune system. Thus, the enzymes involved in regulating and biosynthesis of mycolic acids can be explored as potential drug targets to kill Mycobacterium tuberculosis (Mtb). Herein, Kyoto Encyclopedia of Genes and Genomes is used to understand the fatty acid metabolism signaling pathway and integrative computational approach to identify the novel lead molecules against the mtFabH (β-ketoacyl-acyl carrier protein synthase III), the key regulatory enzyme of the mycolic acid pathway. The structure-based virtual screening of antimycobacterial compounds from ChEMBL library against mtFabH results in the selection of 10 lead molecules. Molecular binding and drug-likeness properties of lead molecules compared with mtFabH inhibitor suggest that only two compounds, ChEMBL414848 (C1) and ChEMBL363794 (C2), may be explored as potential lead molecules. However, the spatial stability and binding free energy estimation of thiolactomycin (TLM) and compounds C1 and C2 with mtFabH using molecular dynamics simulation, followed by molecular mechanics Poisson–Boltzmann surface area (MM/PBSA) indicate the better activity of C2 (ΔG = −14.18 kcal/mol) as compared with TLM (ΔG = −9.21 kcal/mol) and C1 (ΔG = −13.50 kcal/mol). Thus, compound C1 may be explored as promising drug candidate for the structure-based drug designing of mtFabH inhibitors in the therapy of Mtb.</p