UHMWPE Hybrid Nanocomposites for Improved Tribological Performance Under Dry and Water-Lubricated Sliding Conditions

To tap the full potential of polymers to be used as tribo-materials under water lubrication, it is very important to improve their resistance to water uptake on the one hand and improve their strength and load bearing capacity on the other so that their performance under these conditions is not deteriorated. Hence, a unique approach of fabricating a hybrid polymer nanocomposite reinforced with nanoclay for improving the resistance to water uptake and carbon nanotubes (CNTs) to improve the mechanical/tribological properties is undertaken. Ultrahigh molecular weight polyethylene (UHMWPE) hybrid nanocomposites were fabricated via ball milling followed by hot pressing method. Functionalized multi-wall CNTs and C15A organoclay were used as nanofillers in UHMWPE matrix. Hybrid nanocomposites were developed with CNT loadings of 0.5, 1.5 and 3.0 wt% while keeping C15A organoclay content fixed at an optimized value of 1.5 wt%. Initially, the hybrid nanocomposites were optimized under dry sliding conditions whereby a loading of 1.5 wt% of CNTs and 1.5 wt% C15A organoclay resulted in the maximum reduction in the specific wear rate by about 64% as compared to pristine UHMWPE. Later, tribological performance of the optimized hybrid nanocomposite was compared with pristine UHMWPE and its UHMWPE nanocomposites under water-lubricated conditions sliding against a 440C stainless steel ball for 150,000 cycles. The specific wear rate showed a reduction by ~46% for the 1.5 wt% CNTs hybrid nanocomposites as compared to pristine UHMWPE under water lubrication. The improved resistance to wear was attributed to the uniform dispersion of both the nanofillers, namely CNTs and C15A organoclay which effectively increased the load bearing capacity of UHMWPE. Moreover, the excellent barrier properties of the platelet-like structure of C15A clay which presented a torturous path for the diffusion of the water molecule in UHMWPE reduced the softening of the surface layer leading to better resistance to wear under water lubrication.     

A unit-based,cost-efficient scheduler for heterogeneous Hadoop systems

The Journal of Supercomputing - A significant amount of research in the field of job scheduling is carried out in Hadoop. However, there is still need for research to overcome some challenges...     

CAD-integrated analysis of 3-D beams: a surface-integration approach

Most engineering artifacts are designed and analyzed today within a 3-D computer aided design (CAD) environment. However, slender objects such as beams are designed in a 3-D environment, but analyzed using a 1-D beam-element, since their 3-D analysis exhibits locking and/or is computationally inefficient. This process is tedious and error-prone. Here, we propose a dual-representation strategy for designing and analyzing 3-D beams, directly within a 3-D CAD environment. The proposed method exploits classic 1-D beam physics, but is implemented within a 3-D CAD environment by appealing to the divergence theorem. Consequently, the proposed method is numerically and computationally equivalent to classic 1-D beam analysis for uniform cross-section beams. But, more importantly, it closely matches the accuracy of a full-blown 3-D finite element analysis for non-uniform beams.     

Overcoat Free Magnetic Media for Lower Magnetic Spacing and Improved Tribological Properties for Higher Areal Densities

Surface modification with shallow embedding (≤1 nm) of carbon in the top layer of magnetic media is evaluated for its tribological and anti-oxidation properties. Cobalt is used as the magnetic material and carbon embedding is achieved by using the filtered cathodic vacuum arc technique at different ion energies, specifically of 20, 90, and 350 eV, in order to study the effect of ion energy on the embedding profiles. Simulations using the transport of ions in Matter software and X-ray photoelectron spectroscopy (XPS) are used to characterize the embedded layer and their surface chemical composition. XPS and transmission electron microscopy depth profiling results confirm the presence of a shallow mixed layer of carbon and cobalt for all three types of ion energies tested. However, embedding carried out at the ion energy of 90 eV produced a more uniform overcoat free mixed layer (≤1 nm) with improved anti-oxidation properties. Ball-on-disk wear tests and atomic force microscopy based scratch tests are conducted on the bare cobalt and modified cobalt surfaces. It is observed that the wear life and scratch resistance of the cobalt surface improved considerably after surface modification at the ion energy of 90 eV.     

Green synthesis of silver nanoparticles using Zingiber officinale and Thymus vulgaris extracts: characterisation,cell cytotoxicity,and its antifungal activity against Candida albicans in comparison to fluconazole

Fluconazole (FLZ) application as a highly successful commercial antifungal azole agent to treat the fungal infections is limited due to emergence of FLZ‐resistant candida. In this study, the potential of green synthesised silver nanoparticles (NPs) as an antifungal agent against Candida albicans fungal pathogen is investigated. The extract of ginger (Zingiber officinale) and thyme (Thymus vulgaris) plays as reducing agent, capping agent and antifungal agent. The UV–visible spectroscopy shows the peak of surface plasmon resonance of synthesised Ag NPs after a period of time. The synthesised Ag NPs are spherical, with average sizes of 12 and 18 nm based on ginger and thyme extract, respectively. Fourier transform infrared spectroscopy confirms the adsorption of the plant extract on the surface of the as‐prepared Ag NPs. Based on the minimum inhibitory concentration (MIC) method against Candida albicans, the antifungal activity of as‐prepared green synthesised Ag NPs shows higher inhibitory in comparison to FLZ. Finally, the Ag NPs synthesised via thyme extract shows no cytotoxicity with concentration below 3.5 ppm, which can be considered as an appropriate candidate instead of FLZ to treat the superficial fungal infections.Inspec keywords: nanoparticles, surface plasmon resonance, adsorption, nanofabrication, particle size, silver, ultraviolet spectra, antibacterial activity, visible spectra, microorganisms, nanomedicine, Fourier transform infrared spectra, biomedical materials, diseases, materials preparation, cellular biophysicsOther keywords: green synthesis, cell cytotoxicity, antifungal activity, fluconazole application, FLZ‐resistant candida, green synthesised silver nanoparticles, antifungal agent, surface coating, surface plasmon resonance, superficial fungal infections, Zingiber officinale, UV‐visible spectroscopy, Thymus vulgaris extracts, antifungal azole agent, Candida albicans fungal pathogen, plant extracts, ginger, Fourier transform infrared spectroscopy, minimum inhibitory concentration method, Ag     

Effectively designed shell‐tube heat exchangers considering cost minimization and energy management

Cost optimization, which is expressed as a set of analytical variables, is a key objective in economic design approaches of shell‐and‐tube heat exchangers. This study has provided new design techniques based on tube bundle effect on the economic optimization design of shell‐and‐tube heat exchangers. Also the objective of this paper is to develop the cost estimating for the new modified shell‐and‐tube heat exchangers by introducing new objective functions. According to the results the best configuration choice will obviously be the one with the least irreversibility, that is, with the lowest exergy destruction rate and lower annual capital cost. Also, the combined reduction of annual capital investment and operating cost by the new design technique led to a decrease in the overall costs of about 10% to 24% in comparison with original design. So the proposed design technique shows potential for improvement and economic optimization of shell‐and‐tube heat exchangers.     

Synthetic Biology and Tissue Engineering: Toward Fabrication of Complex and Smart Cellular Constructs

Tissue engineering approaches, with the goals of replacing or recovering damaged or diseased tissues, or of reconstituting tissues in vitro for disease modeling and drug development, have the potential to make significant contributions to medicine. Advances in stem cell biology, biomaterial synthesis and characterization, and microscale technologies have made engineered tissues a reality. However, the classic tools used to build tissues in the lab do not allow for complete control of cell behaviors. More recently, synthetic biology principles have developed robust and versatile approaches to program cells with artificial genetic circuits, where cell behavior and function can be manipulated. At the interface between synthetic biology and tissue engineering, there is space for a new area of investigation where material engineering and cellular engineering complement and sustain each other. In this progress report, synthetic biology principles and how they have been used to engineer cells with potential to dictate cell behavior and function in tissue constructs of the future are briefly described. It is believed that this research area still needs further exploration to fully exploit synthetic biology to make smart and functional cellular constructs for therapeutic and in vitro applications.     

Synthesis of zinc oxide nanoparticles reinforced clay and their applications for removal of Pb (Ⅱ) ions from aqueous media

The aim of the study was to synthesize zinc oxide nanoparticles (ZnONPs) composite with clay by a novel route and then to explore the capability of composite of ZnONPs and silty clay (SC) as adsorbents for Pb (Ⅱ) eradication from aqueous media by batch adsorption method. The effect of different operating factors like temperature, pH, dose and time of contact on the adsorption process were studied to optimize the conditions. Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherms were applied for the interpretation of the process. The R2 and q values obtained from Langmuir model suggested that the process is best interpreted by this model. The values of adsorption capacity (qm) noted were 12.43 mg·g-1 and 14.54 mg·g-1 on SC and ZnONPs-SC respectively. The kinetic studies exposed that pseudo second order (PSO) kinetics is followed by the processes suggesting that more than one steps are involved to control the rate of reactions. Various thermodynamic variables such as change in free energy (ΔGΘ), change in enthalpy (ΔHΘ) and change in entropy (ΔSΘ) were calculated. Thermodynamic data suggested that Pb (Ⅱ) adsorption on SC and ZnONPs-SC are spontaneous, endothermic and feasible processes.