Microporous Hydroxyapatite Ceramic Composites as Tissue Engineering Scaffolds: An Experimental and Computational Study

Bone‐tissue engineering mandates the development of multi‐functional bioactive porous hydroxyapatite (HAp) scaffolds. Herein, microwave sintered HAp/ZnO and HAp/Ag composite scaffolds with ≈5–19% porosity are developed using 0–30 vol% graphite as a porogen. The mechanical properties of the porous scaffold are analyzed in detail, revealing that even being more porous, the reinforcement of ZnO (9% porosity, hardness of 2.8 GPa, and toughness of 3.5 MPa.m^1/2) has shown to have better hardness and fracture toughness when compared to Ag (5% porosity, hardness of 1.6 GPa, and toughness of 2.6 MPa.m^1/2). The flexural strength obtained experimentally are complemented with a finite‐element technique that adopts microstructural features in visualizing the effect of porosity on stress distribution. The antibacterial efficacy and cytocompatibility of these composites are validated by increased metabolic activity and conspicuous cell‐matrix interactions. The anticipation of the results reveal that HAp/ZnO (9% porosity) and HAp/Ag (5% porosity) composites can be used as a potential multi‐functional bone implant scaffolds.

     

Coupled heat conduction and deformation in a viscoelastic composite cylinder

We study the coupled problem of deformation due to mechanical and thermal loading of a composite cylinder made up of two layers of linear isotropic viscoelastic materials. The effect of a time-varying temperature field due to unsteady heat conduction on the short term and long term material response is examined in terms of the stress, displacement, and strain fields. The material properties of the two layers of the composite cylinder at any given location and time are assumed to depend on the temperature at that location at that given instant of time. Sequentially coupled analyses of heat conduction and deformation of the viscoelastic composite cylinder are carried out. Analytical solutions for the stress, strain and displacement fields of the viscoelastic composite cylinder are obtained from the corresponding solution of the linear elasticity problem by applying the Correspondence Principle. We examine the discontinuity in the hoop stress and the radial strain at the interface of the two layers caused by mismatches in material properties, during transient heat conduction. We find that the discontinuities change over time as the mismatch in the moduli of the two layers changes due to the material properties which are time-dependent. We also investigate the effect of the thermal field on the time-dependent field variables in the composite body.     

Fermentative hydrogen production by new marine Clostridium amygdalinum strain C9 isolated from offshore crude oil pipeline

The present study investigated hydrogen production potential of novel marine Clostridium amygdalinum strain C9 isolated from oil water mixtures. Batch fermentations were carried out to determine the optimal conditions for the maximum hydrogen production on xylan, xylose, arabinose and starch. Maximum hydrogen production was pH and substrate dependant. The strain C9 favored optimum pH 7.5 (40 mmol H₂/g xylan) from xylan, pH 7.5–8.5 from xylose (2.2–2.5 mol H₂/mol xylose), pH 8.5 from arabinose (1.78 mol H₂/mol arabinose) and pH 7.5 from starch (390 ml H₂/g starch). But the strain C9 exhibited mixed type fermentation was exhibited during xylose fermentation. NaCl is required for the growth and hydrogen production. Distribution of volatile fatty acids was initial pH dependant and substrate dependant. Optimum NaCl requirement for maximum hydrogen production is substrate dependant (10 g NaCl/L for xylose and arabinose, and 7.5 g NaCl/L for xylan and starch).     

Flow due to a porous stretching/shrinking sheet with thermal radiation and mass transpiration

This study investigates the behavior of carbon nanotubes (CNT) approaching an unsteady flow of a Newtonian fluid over a stagnation point on a stretching surface employing porous media. It flows when the liquid begins to move with the progression of time. Heat exchange with the environment has an impact on the flow. The implicitly limited component technique is used to solve the nondimensional partial differential equation with an associated boundary layer, which is an unstable system. Analytically, the solutions, as well as the required boundary conditions, are obtained. The effects of mass transpiration, volume fraction, and heat radiation on Newtonian fluid flow through porous media are explored. Single- and multi-walled CNTs are used as well as water, as base fluids in the experiment. The impact of thermal radiation and heat source/sink is shown in the energy equation, which is solved under four different cases: uniform heat flux case, constant wall temperature case, general power-law wall heat flux case, and general power-law wall temperature case. By supplying distinct physical characteristics, a theoretical analysis of the existence and nonexistence of unique and dual solutions may be explored. These physical parameters determine the velocity distribution and temperature distribution. Prescribed surface temperature (PST) and prescribed wall heat flux (PHF) heat transfer solutions can be written using confluent hypergeometric equations, and generic power-law PST and PHF situations can also be expressed using confluent hypergeometric equations. The graphical representations assist in the discussion of the current study's findings.     

PEG-conjugated highly dispersive multifunctional magnetic multi-walled carbon nanotubes for cellular imaging

We report synthesis of a highly versatile multicomponent nanosystem by covalently decorating the surface of multiwalled carbon nanotubes (CNTs) by magnetite nanoparticles (Fe(3)O(4)), poly(ethylene glycol) (PEG), and fluorophore fluorescein isothiocyanate (FITC). The resulting Fe(3)O(4)-PEG-FITC-CNT nanosystem demonstrates high dispersion ability in an aqueous medium, magnetic responsiveness, and fluorescent capacity. Transmission electron microscopy images revealed that Fe(3)O(4) nanoparticles were well anchored onto the surfaces of the CNT. In vitro time kinetic experiments using confocal microscopy demonstrated a higher uptake of the Fe(3)O(4)-PEG-FITC-CNT nanosystem localized at the perinuclear region of MCF7 cells compared to the free FITC. In addition, the CNT nanosystem demonstrated no evidence of toxicity on cell growth. Surface conjugation of multicomponents, combined with in vitro non-toxicity, enhanced cellular uptake for FITC and site specific targeting ability makes this fluorescent Fe(3)O(4)-PEG-FITC-CNT nanosystem an ideal candidate for bioimaging, both in vitro and in vivo.     

Biohydrogen production by Thermoanaerobacterium thermosaccharolyticum TERI S7 from oil reservoir flow pipeline

Thermophilic dark fermentative hydrogen producing bacterial strain, TERI S7, isolated from an oil reservoir flow pipeline located in Mumbai, India, showed 98% identity with Thermoanaerobacterium thermosaccharolyticum by 16S rRNA gene analysis. It produced 1450–1900 ml/L hydrogen under both acidic and alkaline conditions; at a temperature range of 45–60 °C. The maximum hydrogen yield was 2.5 ± 0.2 mol H₂/mol glucose, 2.2 ± 0.2 mol H₂/mol xylose and 5.2 ± 0.2 mol H₂/mol sucrose, when the respective sugars were used as carbon source. The cumulative hydrogen production, hydrogen production rate and specific hydrogen production rate by the strain TERI S7 with sucrose as carbon source was found to be 1704 ± 105 ml/L, 71 ± 6 ml/L/h and 142 ± 13 ml/g/h respectively. Major soluble metabolites produced during fermentation were acetic acid and butyric acid. The strain TERI S7 was also observed to produce hydrogen continuously up to 48 h at pH 3.9.     

Geometric modeling and local controllability of a spherical mobile robot actuated by an internal pendulum

In this paper, we present the modeling and local equilibrium controllability analysis of a spherical robot. The robot consists of a spherical shell that is internally actuated by a pendulum mechanism. The rolling motion of the sphere manifests itself as a nonholonomic constraint in the modeling. We derive the dynamic model of the system using Lagrangian reduction and the variational principle. We first compute the Lagrangian and identify the symmetry with respect to a group action. The system Lagrangian and the rolling constraint are invariant with respect to the group isotropy and hence permit a reduced dynamic formulation termed as the nonholonomic ‘Euler‐Poincaré’ equation with advected dynamics. Using Lie brackets and symmetric products of the potential and control vector fields, local configuration accessibility and local (fiber) equilibrium controllability are presented. Copyright © 2015 John Wiley & Sons, Ltd.     

RADS: a real-time anomaly detection model for software-defined networks using machine learning

International Journal of Information Security - Software-defined networks (SDN) are no more a new technology as many industries are adopting it in a hybrid or full stack mode. SDN has already...