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Derek Smith

Publications and source records attributed to Derek Smith.

5 recordsLinked to original sources
arXiv2026

Growth Dynamics of S. aureus with Sugars and Sugar Alcohols in Weak Magnetic Fields

We study the effects of weak magnetic fields (around 2 mT) on the growth of Staphylococcus aureus (S. aureus) in the presence of a few sweeteners (monosaccharides, disaccharides, sugar alcohols, and consumer-grade sweeteners). Bacterial growth rates were compared in various magnetic fields at room temperature. Bacterial growth was estimated using optical absorbance measurements at various wavelengths, and pH values were manually estimated using pH strips. Absorbance was measured at 492 nm and 630 nm, which are wavelengths comparable to the size of a cell of S. aureus after division. This comparability plays a vital role in the scale of measured absorbance values. The results imply that bacterial growth may be reduced due to acidic byproducts formed by metabolizing sugars or sugar alcohols, as an increasingly acidic solution is less ideal for bacterial growth. Magnetic fields were also found to have a minor effect on pH estimates. These results reveal potential effects on microorganisms in the presence of sugars and sugar alcohols in addition to weak magnetic fields, demonstrating the contribution of various environmental conditions with increasing prevalence in the modern day.

physics.bio-ph↗
arXiv2018

Growth Pattern of Magnetic Field Treated Bacteria

A study of the induced effect of different types of weak magnetic field exposure on bacterial growth is performed, comparing the relative changes after removal from the magnetic fields. This investigation is relevant to understand the effect of magnetic field exposure on human beings due to electronic devices. For this purpose, we use four species of common bacteria in reference to human health and safety including Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The choice of these four bacteria also allows us to check for effects which rely upon the Gram-staining properties or shapes of bacterial species. These species were initially exposed to static, non-homogeneous and alternating weak magnetic fields, and then they were grown in incubators in the same environment at 37 {\deg}C simultaneously. Comparative measurements of optical density are then used to track the sustained impact on bacterial growth in the experimental samples. Bacteria was first grown in different weak magnetic fields on a plain glass surface both in liquid and solid media. Magnetic field treated bacteria were then transferred into similar test tubes to grow in an incubator concurrently. Bacterial cultures in liquid nutrient broth on plain glass proliferated faster in most species. Different magnetic fields affect the growth pattern of bacteria differently, depending on the bacterial strain. The weak magnetic field seems to decelerate the growth rate, even after the magnetic field is removed. With application of this study, we can potentially investigate the effect of weak field exposures on Eukaryotic cells and gene dynamics.

physics.bio-ph↗
arXiv2017

Stabilization of Dispersion Generalized Benjamin Ono

In this article, we examine $L^2$ well-posedness and stabilization property of the dispersion-generalized Benjamin-Ono equation with periodic boundary conditions. The main ingredient of our proof is a development of dissipation-normalized Bourgain space, which gains smoothing properties simultaneously from dissipation and dispersion within the equation. We will establish a bilinear estimate for the derivative nonlinearity using this space and prove the linear observability inequality leading to small-data stabilization.

math.AP↗
arXiv2015

A new and improved ephemeris for the hot subdwarf eclipsing binary SDSS J082053.53+000843.4

SDSS J082053.53+000843.4 belongs to the HW Vir family of short period binary systems and was first identified by Geier in 2011. Whilst three subsequent papers have focused on the morphology of this system, little has been published on the system period and its constancy. Here we provide the first published times of minima together with a revised ephemeris and a binary period, 0.0962404(1)d, that is four orders of magnitude more precise than previous declared values.

astro-ph.SR↗