Friction and wear characteristics of organic thiophosphoro derivatives — a critical appraisal

The friction- and wear-reducing characteristics of a number of oil soluble sulphurised and phosphosulphurised derivatives for automotive and industrial applications have been reviewed. A critical appraisal of the suggested causes and mechanism of friction reduction and antiwear characteristics has been made. A review of the investigations carried out so far indicates that the creation of in situ films of simple inorganic salts, such as molybdenum disulphide, iron sulphide or phosphates of low shear strength and lamellar structures, does not appear to be the primary cause of low friction and wear. The authors have, therefore, undertaken a programme to synthesise and study the chemistry and tribochemical reactions in relation to friction and wear characteristics of hydrocarbon-soluble thiophosphoro derivatives of alkyl phenol, alcohols and fatty esters, in order to establish relationships between the reactivity, chemical nature and crystal structure of films formed on rubbing surfaces, and antifriction and antiwear characteristics. Molybdenum salts of various phosphorothio derivatives of pentadecylphenol and lauryl oleate of specific structures have been synthesised, and the friction and wear properties of their blends in mineral oil base stock have been studied. It can be clearly inferred from the results that type of bonding between sulphur, phosphorus and molybdenum, and reactivity of these derivatives with rubbing surfaces, determine their friction-reducing and antiwear characteristics. Their reactivity with iron and the nature of films formed are under investigation.     

Effect of low frequency ultrasonic assisted extraction on the quality of seed oils of Indian origin

The study gives an insight into the effect of low frequency ultrasonic enhancement of solvent extraction on the quality of non-edible oils (Jatropha and Pongamia as model seed varieties) in comparison to conventional methods of extraction i.e. direct reflux or soxhlet extraction using hexane. A series of experiments have been carried out to study the effect of variables; solute to solvent ratio (1:2.5-1:10) and reaction time (30 s-60 min) on the yield of oil. The quality of oil extracted by different methods have been assessed by determining the acid value of oil by ASTM D-974/04 method, a measurement of triglyceride and fatty acid degradation, by the presence of phorbol esters in Jatropha curcas and phenolic compounds in Pongamia oil analyzed using HPLC. Under optimized conditions solute to solvent ratio of 1:10 (w/v), 3 min extraction time yields > 95% pure oil having < 1% FFA in Jatropha curcas and 30 s extraction time in Pongamia seed yields oil with less than 2% FFA in comparison to conventional method of extraction in 16 h.     

Supercritical carbon dioxide–assisted synthesis of stimuli-responsive magnetic poly(N-isopropylacrylamide)–ferrite biocompatible nanocomposites for targeted and controlled drug delivery

Supercritical carbon dioxide–assisted synthesis of poly(N-isopropylacrylamide)–ferrite nanocomposites was carried out by polymerization reaction of N-isopropyl acrylamide monomer in the presence of ferrite nanoparticles. They were characterized by Fourier transform infrared, X-ray diffraction, transmission electron microscopy, atomic force microscopy, and vibrating sample magnetometry analysis. Drug loading and release profiles were studied. Nanomaterials showed pH-dependent drug release profile. Polymer nanocomposites in comparison to ferrite nanoparticles showed impressive drug release activity, with a release percent of 20.98–76.54%, and greater biocompatibility in breast cancer cells, with a cell viability of 81–93%. This pH-dependent drug release activity and magnetic property of polymer nanocomposites can be used for controlled and targeted drug delivery.     

Effect of functionalized silicon carbide nano-particles as additive in cross-linked PVA based composites for vibration damping application

In this research study, a comprehensive effort has been made to functionalize silicon carbide particles using the acidic oxidation with nitric acid to obtain homogeneous stabilized distribution of activated SiC particles within a polymer matrix, and develop functionalized silicon carbide (f-SiC) particle reinforced polyvinyl alcohol (PVA) based cross-linked composite. After fabrication of functionalized silicon carbide (f-SiC) particle reinforced polyvinyl alcohol based cross-linked composite with varying f-SiC weight percentages of PVA (0%, 1%, 2%, 3%, and 4%) were placed to various investigations. Processed samples are initially examined based by the physical tests (water absorption tests), followed by mechanical test (tensile test) and then micro-structural tests (scanning electron microscopy). Lastly, thermal tests were also concluded which involved the dynamic mechanical, differential thermal and thermo gravimetric analysis. The cross-linked polyvinyl alcohol-based composite with 2 weight % of f-SiC content is observed to be the superlative of all the compositions under this research study that was confirmed by the mechanical and micro-structural tests. This composite material shows high storage modulus with visco-elastic behavior, therefore, the material can be utilized to diminish the transmission of noise, as a shock absorber and vibration isolator.     

Determining the number of layers in graphene films synthesized by filtered cathodic vacuum arc technique

We have synthesized graphene film by the filtered cathodic vacuum arc (FCVA) technique and determined the number of layers in graphene films by various techniques. Amorphous carbon (a-C) films of different thicknesses (1, 2, 3, 6, 10 and 18 nm) were synthesized by the FCVA technique on Si/SiO₂/Ni substrate and then annealed in vacuum at 800°C and cooled down to room temperature naturally to obtain graphene. Prepared graphene films were transferred on different substrates and characterized by the Raman spectroscopy, UV-VIS-NIR spectroscopy, high-resolution transmission electron microscopy (HRTEM), optical microscopy, atomic force microscopy (AFM) and sheet resistance to determine the number of layers present in the graphene films. Raman spectra of the prepared graphene films exhibit that there is red shift in the position of D, G and 2 D peak. The value of I_2D/I_G varied from 0.18 to 0.51, I_D/I_G varied from 0.82 to 1.02 and full width at half maximum of 2 D peak varied from 101.2 to 128.0 cm^?1, for different thicknesses of graphene films, respectively. The value of transmittance decreases from 97 to 63.7% and that of sheet resistance increases from 460 to 1400 Ω/square with the increase in the thickness of the prepared graphene film. The HRTEM and AFM study revealed that the graphene synthesis from 1 nm thick a-C film possesses a single layer structure.     

Serological distinction of integral plasma membrane proteins as a class of mycobacterial antigens and their relevance for human T cell activation

This study pertains to classification and antigenic analysis of mycobacterial plasma membrane proteins in relation to human T cell proliferative responses, using a 'fast grower' Mycobacterium fortuitum as model. Membrane vesicles, prepared by sonication and differential centrifugation, were subjected to biphasic Triton X-114 extraction for isolation of integral peripheral (aqueous phase) proteins. Neither protein pool showed any appreciable overlap serologically. SDS-PAGE showed five prominent bands in peripheral and three in the integral protein pool, whereas immunoblotting with rabbit antisera identified only two major antigens (60 and 67 kD) in the former and five (24, 34, 42, 51 and 54 kD) in the latter. ELISA with a panel of anti-mycobacterial MoAbs revealed that nine out of 12 previously known antigens were present in the peripheral protein pool. Only two of them (33 and 40 kD) were additionally detected amongst integral proteins. The membrane-associated immunosuppressive moiety lipoarabinomannan was semiquantitatively located in aqueous phase. In bulk T cell proliferation assays, seven out of 10 subjects belonging to a 'responder' background (BT-BB leprosy patients and healthy contacts) showed high responses for Myco. fortuitum antigens. Proliferative response with integral proteins was comparable to that with whole membrane, but it was significantly higher (P < 0.0005) than the response with peripheral proteins. The distinction and relevance of integral membrane proteins as a class of mycobacterial antigens make them worthy of consideration in a subunit vaccine design.     

Sulphurization of jojoba oil for application as extreme pressure additive

In order to develop jojoba oil-based extreme pressure (E P) additives, a number of sulphurized jojoba oils have been prepared by varying the reaction conditions. The products differ in their amount of sulphur and in their structure. An attempt to predict their performance based on their structure reveals that it is not a simple addition of sulphur which is required; a certain level of cross linking and polymerization also are desirable to have a product which is effective as an E P additive.     

Chemical composition and antifungal activity of essential oils from three Himalayan Erigeron species

Three Himalayan Erigeron (Asteraceae) species viz Erigeron mucronatus, Erigeron annuus and Erigeron karwinskianus growing in sub-alpine region revealed occurrence of isomeric polyacetylenic constituents viz., matricaria and lachnophyllum esters which accounted for 83.3%, 69.3% and 30.1% of the essential oils from these species, respectively, in addition to mono- and sesquiterpenoids as minor constituents. The antifungal activity tested by poisoned food (PF) techniques against Fusarium oxysporum, Helminthosporium maydis, Rhizoctonia solani, Alternaria solani and Sclerotinia sclerotiorum demonstrated significant inhibition of the mycelial growth of all strains (p < 0.05). The oils (500 μg/mL) showed significant antifungal effect against tested fungi in the growth inhibition range of 37.6–85.5% with respective IC₅₀ values ranging from 88.8 to 660.0 μg/mL as compared to standard fungicides (100% inhibition) with IC₅₀ value in the range of 32.2–129.4 μg/mL. Significant inhibition of spore germination was noticed for F. oxysporum, Curvularia lunata and Albugo candida which were highly susceptible to E. annuus oil with their IC₅₀ values 120.7, 253.5 and 300.4 μg/mL, respectively. Thus, the results obtained in this study demonstrate the potential of essential oils from Himalayan Erigeron species as non-toxic, eco-friendly and biodegradable natural fungicides.     

Comparative analysis of a Sisko nanofluid over a stretching cylinder through a porous medium

The present article examines the Sisko nanofluid flow and heat transfer through a porous medium due to a stretching cylinder using Buongiorno's model for nanofluids. Suitable similarity transformations are used to transform the governing boundary layer equations of fluid flow into nonlinear ordinary differential equations. The finite difference method is used to solve coupled nonlinear differential equations with MATLAB software. The impact of different parameters viz., the Sisko material parameter, porosity parameter, curvature parameter, thermophoresis parameter, and Brownian diffusion parameter on the velocity and temperature distribution are presented graphically. Moreover, the effect of the involved parameters on the heat transfer rate is also studied and presented through table values. It is noticed from the numerical values that the porosity parameter reduces the velocity while enhancing the temperature. The curvature parameter enhances the velocity throughout the fluid regime and reduces the temperature near the surface while enhancing the temperature far away from the surface. The study reveals that the thermophoresis and Brownian diffusion parameters that characterize the nanofluid flow reduce the wall heat transfer rate, while the curvature parameter enhances it. This investigation of wall heating/cooling has essential applications in solar porous water absorber systems, chemical engineering, metallurgy, material processing, and so forth.