Effect of Zn and Co doping on antibacterial efficacy and cytocompatibility of spark plasma sintered hydroxyapatite

Hydroxyapatite [Hap, Ca₁₀(PO₄)₆(OH)₂] is one of the most preferred bioceramic material for orthopedic implants and coatings due to its stoichiometric similarities with human hard tissues. However, foreign body implantation inside human body sometimes leads to bacterial film formation over the implant surface causing the implant failure, thereby needing a revision surgery. This study attempts to select the better dopant between zinc (Zn) and cobalt (Co) as per the antibacterial efficacy when doped in Hap. To prepare antibacterial transition-metal-doped Hap, Zn and Co are doped in Hap as per the chemical formula Ca_10−x M_x(PO₄)₆(OH)₂, (M = Zn or Co and x = 0.24) to improve antibacterial efficacy. Phase and microstructural characterization by Rietveld refinement, scanning electron microscopy (SEM), and Fourier transformation infrared spectroscopy (FT-IR) confirms the doping. Evaluation of antibacterial activity against E coli reveals that both Zn- and Co-doped Hap shows antibacterial property with the latter being more effective (zone of inhibition ~3 mm more) for the same level of doping. Inductively coupled plasma-mass spectrometry confirms the presence of ~676 ppb Co⁺² and ~303 ppb Zn⁺² after leaching. In addition, cytotoxicity assay with NIH3T3 cell line reveals cytocompatibility of both the compositions with either dopant. The effect of spark plasma sintering on densification and mechanical properties of Co-doped Hap is investigated for the first time and compared with Hap with the same level of Zn doping. It appears that Co-doped Hap attains higher densification (~7% more) and fracture toughness (~2 times better) as compared to that of Zn-doped counterpart (densification: 86% and fracture toughness: 0.75 ± 0.12 MPa √m). Thus, this study suggests that Co- and Zn-doped Hap are promising candidates for bone tissue engineering with improved antibacterial properties and in addition, Co-doped Hap can attain higher density and offer better fracture toughness than that of Hap doped with Zn.     

A comparative study on the performance, emission and combustion studies of a DI diesel engine using distilled tyre pyrolysis oil–diesel blends

Alternate fuels like ethanol, biodiesel, LPG, CNG, etc., have been already commercialised in the transport sector. In this context, pyrolysis of solid waste is currently receiving renewed interest. The disposal of waste tyres can be simplified to a certain extent by pyrolysis. In the present work, the crude tyre pyrolyisis oil (TPO) was desulphurised and then distilled through vacuum distillation. Also, two distilled tyre pyrolysis oil (DTPO)–diesel fuel (DF) blends at lower and higher concentrations were used as fuels in a four stroke single cylinder air cooled diesel engine without any engine modification. The results were compared with diesel fuel (DF) operation. Results indicate that the engine can run with 90% DTPO and 10% diesel fuel.     

Effect of low-temperature oxidation on the pyrolysis and combustion of whole oil

Low-temperature oxidation (LTO) of the Fosterton crude oil mixed with its reservoir sand has been investigated in a tubular reactor. Reservoir sand saturated with 15 wt% of crude oil (20.5° API gravity) was subjected to air injection at low-temperature (220 °C) for a period of time (17 h and 30 min), resulting in the formation of an oxygenated hydrocarbon fuel. The vent gases were analyzed for the content of CO, CO₂, and oxygen and the residue was analyzed to determine the elemental composition and calorific value. The presence of LTO region was verified from the values of apparent H/C ratio. In addition, thermal behavior and combustion kinetics of the residue was investigated using thermogravimetric analysis (TGA). TG involves both non-isothermal and isothermal analysis and kinetic data was derived from isothermal studies. The general model for nth order reaction was used to obtain the kinetic parameters of the coke oxidation reaction. The activation energy, frequency factor and order of the reactions were determined using the model.     

Characteristics of pulse electrodeposited AgGaSe2 films

In this work, the pulse electrodeposition technique has been employed for the first time to deposit AgGaSe₂ films. The films were deposited at room temperature from a bath containing Analar grade 10 mM silver nitrate, 10 mM gallium nitrate and 10 mM SeO₂. The deposition potential was maintained as—0.68 V (SCE). Tin oxide coated glass substrates (5.0 ohms/sq) was used as the substrate. The duty cycle was varied in the range of 6–50 %. The XRD profile of the thin films deposited at different duty cycles indicate the peaks corresponding to AgGaSe₂. Atomic force microscopy studies indicated that the surface roughness increased from 0.95 to 1.25 nm with duty cycle. The transmission spectra exhibited interference fringes. Refractive index of 2.71 was observed in the wavelength range 600–1,000 nm. Electrochemical Impedance studies indicated a single semicircle. The grain boundary resistance decreased with increase of duty cycle.     

Rapid Microwave‐Assisted Solvothermal Synthesis of Methanol Tolerant Pt–Pd–Co Nanoalloy Electrocatalysts

We report here a microwave‐assisted solvothermal (MW‐ST) method to synthesise carbon‐supported multimetallic nanostructured alloys of Pt, Pd and Co with high crystallinity and homogeneity for electrocatalytic application in fuel cells. Multimetallic nanoalloy electrocatalysts have been synthesised by a one‐pot, rapid MW‐ST method within 15 min at <300 °C without any post‐annealing in reducing gas atmospheres. For a comparison, same multimetallic alloys were also synthesised by heat treatment of co‐precipitated metals. Significant differences were observed in the phase structure and surface composition of the alloys synthesised by the two methods, which were rationalised based on the synthesis procedures adopted. Further, the multimetallic alloys were also explored for their electrocatalytic applications as cathode catalysts for oxygen reduction reaction (ORR). The multimetallic alloys, synthesised by the MW‐ST method, show much higher ORR activity compared to their counterparts synthesised by the conventional borohydride reduction method. While the ORR activity of Pt₇₀Pd₂₀Co₁₀ is comparable to that of commercial Pt, the ORR activity of Pt₅₀Pd₃₀Co₂₀ in direct methanol fuel cells (DMFC) is superior to that of commercial Pt at high methanol concentrations due to its high tolerance to methanol that may crossover from the anode to the cathode.     

Sorting, selection, and routing on the array with reconfigurableoptical buses

In this paper, we present efficient algorithms for sorting, selection, and packet routing on the AROB (Array with Reconfigurable Optical Buses) model. One of our sorting algorithms sorts n general keys in O(1) time on an AROB of size n^ϵ×n for any constant ϵ>0. We also show that selection from out of n elements can be done in randomized O(1) time employing n processors. Our routing algorithm can route any h-relation in randomized O(h) time. All these algorithms are clearly optimal