89 research outputs found

    Monitoring of wild pseudomonas biofilm strain conditions using statistical characterization of scanning electron microscopy images

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    This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The present paper proposes a novel method of quantification of the variation in biofilm architecture, in correlation with the alteration of growth conditions that include variations of the substrate and conditioning layer. The polymeric biomaterials serving as substrates are widely used in implants and indwelling medical devices, while the plasma proteins serve as the conditioning layer. The present method uses descriptive statistics of field emission scanning electron microscopy (FESEM) images of biofilms obtained during a variety of growth conditions. We aim to explore here the texture and fractal analysis techniques, to identify the most discriminatory features which are capable of predicting the difference in biofilm growth conditions. We initially extract some statistical features of biofilm images on bare polymer surfaces, followed by those on the same substrates adsorbed with two different types of plasma proteins, viz., bovine serum albumin (BSA) and fibronectin (FN), for two different adsorption times. The present analysis has the potential to act as a futuristic technology for developing a computerized monitoring system in hospitals with automated image analysis and feature extraction, which may be used to predict the growth profile of an emerging biofilm on surgical implants or similar medical applications.SDS acknowledges the funding from the Department of Science and Technology (DST), Govt. of India through the Women’s Scientist Scheme – A, project no. LS-466/WOS A/2012-2013

    Fractal analysis of AFM images of worn-out contact lens inner surface

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    Interesovanje za tehnologiju površina biomaterijala podstaklo je istraživanje unutrašnje površine gas-propusnih kontaktnih sočiva, uz korišćenje skenirajućeg mikroskopa za snimanje. Topografski i fazni snimci su prikupljeni radi ispitivanja površinske hrapavosti i svojstava nakon produženog perioda nošenja kontaktnog sočiva. Analiza se zasniva na fraktalnom pristupu primenjenom u Matlab okruženju za analizu slike. Fraktalna dimenzija određena 'metodom nebodera', je korišćena za identifikaciju i dodatno pojašnjenje funkcionalnog ponašanja površine. Autori su želeli da istaknu da je vreme nošenja gas- propusnih sočiva komercijalna kategorija u pogledu učestalosti zamene sočiva i da samo značajne promene svojstava površine čine zamenu neophodnom.The interest in biomaterials surface technology has led to an investigation of rigid gas permeable contact lens inner surface using scanning probe microscopy for measurement. Topography and phase images were recorded in order to investigate surface roughness and properties after an extended period of contact lens wearing. Analysis is based on fractal approach incorporated with MatLab software for image processing. The fractal dimension, calculated by skyscrapers method, is used for surface identification and subsequently for surface behavior explanation. The authors' aim is to point out that time is merely a commercial category for rigid gas permeable contact lens replacement and that only significant changes in surface properties render such replacement necessary

    Fractal analysis of AFM images of worn-out contact lens inner surface

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    Interesovanje za tehnologiju površina biomaterijala podstaklo je istraživanje unutrašnje površine gas-propusnih kontaktnih sočiva, uz korišćenje skenirajućeg mikroskopa za snimanje. Topografski i fazni snimci su prikupljeni radi ispitivanja površinske hrapavosti i svojstava nakon produženog perioda nošenja kontaktnog sočiva. Analiza se zasniva na fraktalnom pristupu primenjenom u Matlab okruženju za analizu slike. Fraktalna dimenzija određena 'metodom nebodera', je korišćena za identifikaciju i dodatno pojašnjenje funkcionalnog ponašanja površine. Autori su želeli da istaknu da je vreme nošenja gas- propusnih sočiva komercijalna kategorija u pogledu učestalosti zamene sočiva i da samo značajne promene svojstava površine čine zamenu neophodnom.The interest in biomaterials surface technology has led to an investigation of rigid gas permeable contact lens inner surface using scanning probe microscopy for measurement. Topography and phase images were recorded in order to investigate surface roughness and properties after an extended period of contact lens wearing. Analysis is based on fractal approach incorporated with MatLab software for image processing. The fractal dimension, calculated by skyscrapers method, is used for surface identification and subsequently for surface behavior explanation. The authors' aim is to point out that time is merely a commercial category for rigid gas permeable contact lens replacement and that only significant changes in surface properties render such replacement necessary

    Quantifying the pattern of microbial cell dispersion, density and clustering on surfaces of differing chemistries and topographies using multifractal analysis

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    The effects of surface topography on bacterial distribution across a surface are of extreme importance when designing novel, hygienic or antimicrobial surface coatings. The majority of methods that are deployed to describe the pattern of cell dispersion, density and clustering across surfaces are currently qualitative. This paper presents a novel application of multifractal analysis to quantitatively measure these factors using medically relevant microorganisms (Staphylococcus aureus or Staphylococcus epidermidis). Surfaces (medical grade 316 stainless steel) and coatings (Ti–ZrN, Ti–ZrN/6.0%Ag, Ti–ZrN/15.6%Ag, TiZrN/24.7%Ag) were used in microbiological retention assays. Results demonstrated that S. aureus displayed a more heterogeneous cell dispersion (∆αAS < 1) whilst the dispersion of S. epidermidis was more symmetric and homogeneous (∆αAS ≥ 1). Further, although the surface topography and chemistry had an effect on cell dispersion, density and clustering, the type of bonding that occurred at the surface interface was also important. Both types of cells were influenced by both surface topographical and chemical effects; however, S. aureus was influenced marginally more by surface chemistry whilst S. epidermidis cells was influenced marginally more by surface topography. Thus, this effect was bacterially species specific. The results demonstrate that multifractal analysis is a method that can be used to quantitatively analyse the cell dispersion, density and clustering of retained microorganisms on surfaces. Using quantitative descriptors has the potential to aid the understanding the effect of surface properties on the production of hygienic and antimicrobial coatings

    Applied Fracture Mechanics

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    The book "Applied Fracture Mechanics" presents a collection of articles on application of fracture mechanics methods to materials science, medicine, and engineering. In thirteen chapters, a wide range of topics is discussed, including strength of biological tissues, safety of nuclear reactor components, fatigue effects in pipelines, environmental effects on fracture among others. In addition, the book presents mathematical and computational methods underlying the fracture mechanics applications, and also developments in statistical modeling of fatigue. The work presented in this book will be useful, effective, and beneficial to mechanical engineers, civil engineers, and material scientists from industry, research, and education

    Electrochemical method for the determination of arsenic 'in the field' using screen-printed grid electrodes

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    This project describes development and problem solving efforts to realise a viable portable sensor for arsenic, applicable to drinking water. The work is the first dedicated effort towards this goal, after the preliminary investigations previously conducted at Cranfield University (Cooper, 2004 and Noh, 2005). Using polymeric gold ink BQ331 (DuPont Microcircuit Materials, Bristol, UK) as working electrode on screen printed strips, the electrochemical procedure was studied. Due to the wealth of research on electrochemical and non electrochemical methods for arsenic determination, this project attempts to capitalise on the unique advantages of the screen-printed gold surface. In particular, the issues surrounding the performance of the sensor were evaluated by electrochemical and spectroscopic means (including infrared, nuclear magnetic resonance and X-ray photoelectron spectroscopy). A number of custom screen printed electrodes were prepared in house comparing sensor performance on compositional factors. An interference coming from silver interaction with chloride in the reference electrode was identified. As such, the design of the sensor needs to change to include either an immobilising layer, such as Nafion, over the silver, or to omit screen-printed silver altogether. The Nafion was presumed to work by excluding (or at least much reducing) the passage of negatively charged chloride ions to the silver surface preventing formation of soluble silver chloride complexes. The design of the sensor was considered in light of performance and sensitivity. The screen-printed electrodes were cut to facilitate a microband design lending favourable diffusive to capacitive current characteristics. With this design, As(III) detection was demonstrated comfortably at 5 ppb (in a copper tolerant 4 M HCl electrolyte) without electrode need for additional preparation procedures. This is below the World Health Organisation (WHO) guideline and United States Environmental Protection Agency (USEPA) regulation level of 10 ppb in drinking water. The electrode materials are already mass manufacturable at an estimated cost less than £ 0.5 per electrode. Themicroband design could, in principle, be applied to mercury and other metal ions. The procedure for As(V) either with chemical or electrochemical reduction and determination still needs to be assessed. However, the presented electrode system offers a viable alternative to the colorimetric test kits presently employed around the world for arsenic in drinking water. Also, the Nicholson Method (Nicholson, 1965a), used for characterising electron transfer kinetics at electrode surfaces, was extended for application to rough surfaces using a fractal parameter introduced by Nyikos and Pajkossy (1988). This work includes mathematical derivation and numerical evaluation and gives a number of predictions for electrochemical behaviour. These predictions could not be tested experimentally, as yet, since the physical conditions must be carefully controlled

    Fractal analyses of some natural systems

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    Fractal dimensions are estimated by the box-counting method for real world data sets and for mathematical models of three natural systems. 1 he natural systems are nearshore sea wave profiles, the topography of Shei-pa National Park in Taiwan, and the normalised difference vegetation index (NDV1) image of a fresh fern. I he mathematical models which represent the natural systems utilise multi-frequency sinusoids for the sea waves, a synthetic digital elevation model constructed by the mid-point displacement method for the topography and the Iterated Function System (IFS) codes for the fern leaf. The results show that similar fractal dimensions are obtained for discrete sub-sections of the real and synthetic one-dimensional wave data, whilst different fractal dimensions are obtained for discrete sections of the real and synthetic topographical and fern data. The similarities and differences are interpreted in the context of system evolution which was introduced by Mandelbrot (1977). Finally, the results for the fern images show that use of fractal dimensions can successfully separate void and filled elements of the two-dimensional series
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