Enhanced Antibacterial Activity of Bifunctional Fe_(3)O_(4)-Ag Core-Shell Nanostructures

We describe a simple one-pot thermal decomposition method for the production of a stable colloidal suspension of narrowly dispersed superparamagnetic Fe_(3)O_(4)-Ag core-shell nanostructures.These biocompatible nanostructures are highly toxic to microorganisms.Antimicrobial activity studies were carried out on both Gram negative(Escherichia coli and Proteus vulgaris)and Gram positive(Bacillus megaterium and Staphylococcus aureus)bacterial strains.Efforts have been made to understand the underlying molecular mechanism of such antibacterial actions.The effect of the core-shell nanostructures on Gram negative strains was found to be better than that observed for silver nanoparticles.The minimum inhibitory concentration(MIC)values of these nanostructures were found to be considerably lower than those of commercially available antibiotics.We attribute this enhanced antibacterial effect of the nanostructures to their stability as a colloid in the medium,which modulates the phosphotyrosine profile of the bacterial proteins and arrests bacterial growth.We also demonstrate that these core-shell nanostructures can be removed from the medium by means of an external magnetic field which provides a mechanism to prevent uncontrolled waste disposal of these potentially hazardous nanostructures.

Cosmic acceleration with bulk viscosity in an anisotropic f(R, Lm) background

In this article,we investigate the observed cosmic acceleration in the framework of a cosmological f(R,Lm)model dominated by bulk viscous matter in an anisotropic background.We consider the locally rotationally symmetric Bianchi type I metric and derive the Friedmann equations that drive the gravitational interactions in f((R,Lm)gravity.Further,we assume the functional form f(R,Lm)=R/2+Lαm,where a is a free model parameter,and then find the exact solutions of field equations corresponding to our viscous matter dominated model.We incorporate the updated H(z)data and the Pantheon data to acquire the best-fit values of parameters of our model by utilizing theχ2 minimization technique along with the Markov Chain Monte Carlo random sampling method.Further,we present the behavior of physical parameters that describe the Universe’s evolution phase,such as density,effective pressure and EoS parameters,skewness parameter,and the statefinder diagnostic parameters.We find that the energy density indicates expected positive behavior,whereas the negative behavior of bulk viscous pressure contributes to the Universe’s expansion.The effective EoS parameter favors the accelerating phase of the Universe’s expansion.Moreover,the skewness parameter shows the anisotropic nature of spacetime during the entire evolution phase of the Universe.Finally,from the statefinder diagnostic test,we found that our cosmological f(R,Lm)model lies in the quintessence region,and it behaves like a de-Sitter universe in the far future.We analyze different energy conditions in order to test the consistency of the obtained solution.We find that all energy conditions except strong energy condition(SEC)show positive behavior,while the violation of SEC favors the recently observed acceleration with the transition from decelerated to an accelerated epoch of the Universe’s expansion in the recent past.

Tidal force effects and bound orbits in null naked singularity spacetime

Naked singularities form during the gravitational collapse of inhomogeneous matter clouds.The final nature of the singularity depends on the initial conditions of the matter properties and types of matter profiles.These naked singularities can also be divided into two types:null-like and timelike singularities.The spacelike singularity of the Schwarzschild black hole can be distinguished from the null and timelike naked singularity spacetimes.In light of this,we investigate the precession of timelike bound orbits in the null naked singularity spacetime,as well as tidal force effects and geodesic deviation features.As a result,we find that the orbital precession of the timelike bound orbits in null naked singularity spacetime could be distinguished from the Schwarzschild precession case.The radial component of the tidal force has an intriguing profile,whereas the angular component has a profile that is comparable to that of a Schwarzschild black hole scenario.The geodesic deviation equation is then solved numerically,yielding results that resemble Schwarzschild black holes.These characteristic features can then be used to discern among these singularities.