Machinery health prognostics: A systematic review from data acquisition to RUL prediction

Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.

http://envismadrasuniv.org/Bioremediation/pdf/Interactions%20of%20chromium%20with%20microorganisms.pdf

Interactions of chromium with microorganisms and plants

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

/pdf/complicated-catheter-associated-urinary-tract-infections-due-4k0xw7kb6h.pdf

Complicated Catheter-Associated Urinary Tract Infections Due to Escherichia coli and Proteus mirabilis

A study was undertaken to examine the effects of the heavy metals copper, lead, and zinc on biofilm and planktonic Pseudomonas aeruginosa. A rotating-disk biofilm reactor was used to generate biofilm and free-swimming cultures to test their relative levels of resistance to heavy metals. It was determined that biofilms were anywhere from 2 to 600 times more resistant to heavy metal stress than free-swimming cells. When planktonic cells at different stages of growth were examined, it was found that logarithmically growing cells were more resistant to copper and lead stress than stationary-phase cells. However, biofilms were observed to be more resistant to heavy metals than either stationary-phase or logarithmically growing planktonic cells. Microscopy was used to evaluate the effect of copper stress on a mature P. aeruginosa biofilm. The exterior of the biofilm was preferentially killed after exposure to elevated concentrations of copper, and the majority of living cells were near the substratum. A potential explanation for this is that the extracellular polymeric substances that encase a biofilm may be responsible for protecting cells from heavy metal stress by binding the heavy metals and retarding their diffusion within the biofilm.

Heavy metal resistance of biofilm and planktonic Pseudomonas aeruginosa.

http://doras.dcu.ie/17607/1/Review_of_residual_stresses-Final.pdf

Methods of measuring residual stresses in components

The metal-binding affinity of the anionic poly-γ-d-glutamyl capsule of Bacillus licheniformis was investigated by using Na+, Mg2+, Al3+, Ca2+, Cr3+, Mn2+, Fe3+, Ni2+, and Cu2+. Purified capsule was suspended in various concentrations of the chloride salts of the various metals, and after dialysis the bound metals were analyzed either by graphite furnace atomic absorption spectroscopy or by inductively coupled plasma-mass spectrometry. Exposure of purified capsule to excess concentrations of Na+ revealed it to contain 8.2 μmol of anionic sites per mg on the basis of Na binding. This was confirmed by titration of the capsule with HCl and NaOH. Other metal ions were then added in ionic concentrations equivalent to 25, 50, 75, 100, 200, and 400% of the available anionic sites. The binding characteristics varied with the metal being investigated. Addition of Cu2+, Al3+, Cr3+, or Fe3+ induced flocculation. These metal ions showed the greatest affinity for B. licheniformis capsule in competitive-binding experiments. Flocculation was not seen with the addition of other metal ions. With the exception of Ni2+ and Fe3+ all capsule-metal-binding sites readily saturated. Ni2+ had low affinity for the polymer, and its binding was increased at high metal concentrations. Fe3+ binding resulted in the development of rust-colored ferrihydrite which itself could bind additional metal. Metal-binding characteristics of B. licheniformis capsule appear to be influenced by the chemical and physical properties of both the capsule and the metal ions.

Metal-Binding Characteristics of the Gamma-Glutamyl Capsular Polymer of Bacillus licheniformis ATCC 9945.

https://www.physics.queensu.ca/~lynann/references/research8.pdf

Plastic versus elastic deformation effects on magnetic Barkhausen noise in steel

An analytical model was developed to determine the length of a surface-breaking defect along the direction of the applied field when using the magnetic flux leakage (MFL) non-destructive technique. The theoretical model fits the experimental MFL results from simulated defects. The extreme positions of the normal magnetic leakage field component were subsequently used for a quantitative evaluation of the defect length. Permeability variations were neglected by employing a flux density close to sample saturation. Four different defect geometries were experimentally investigated and the validity of the analytical model was verified. Good agreement between theoretical and experimental results suggests that this method can be used as an inverse MFL data interpretation technique.

https://www.physics.queensu.ca/~lynann/references/research16.pdf

A model for magnetic flux leakage signal predictions

Angular‐dependent magnetic Barkhausen noise (MBN) measurements were performed on a pipeline steel sample for various values of applied uniaxial stress at three angles with respect to the sample’s zero stress magnetic easy axis direction. It was observed that the response of the MBN signal to stress was dependent upon the direction of the stress with respect to the zero stress easy axis. The stress response of the MBN signal was greatest for (i) tensile stresses oriented perpendicular to the zero stress easy axis direction and (ii) compressive stresses applied parallel to the easy axis direction. The modification of the MBN signal under an applied stress was attributed primarily to a change in the 180° domain wall population in the material investigated. Results were described by a model that considered regions of locally correlated domain behavior, termed ‘‘interaction regions,’’ that were typically the size of grains within the steel material. A basic result of the model was the stress required to modify the number of 180° domain walls within an interaction region. Theoretical calculations of these threshold stresses for a typical grain size were found to be in agreement with the range of applied stresses that was observed to modify the angular‐dependent MBN signal obtained from the sample.

Investigation of the stress‐dependent magnetic easy axis in steel using magnetic Barkhausen noise

The angular dependence of magnetic Barkhausen noise (MBN) on eight surfaces through the thickness of a 2% Mn steel pipeline sample was investigated. The MBN signal was analyzed by integrating the square of the MBN voltage signal with respect to the time axis. The resulting value, referred to as the MBN energy signal, was modeled by considering the irreversible motion of 180° domain walls, under the influence of an oriented magnetic field. An expression for the angular dependence of the MBN energy signal was derived and was given by energy=α cos2 θ+β, where α and β are the fitting parameters and θ is the angle between the maximum MBN signal and the applied sweep field. The α parameter was associated with the irreversible motion of 180° walls that contributed to the net macroscopic easy axis near the surface of the sample, while the β parameter was associated with the isotropic background MBN signal. The energy equation could be used to fit the data for all sweep field amplitudes in which the MBN spectrum was observed. A dependence of the α and β parameters on the applied sweep field amplitude was observed.

Lynann Clapham

Papers

Metal-Binding Characteristics of the Gamma-Glutamyl Capsular Polymer of Bacillus licheniformis ATCC 9945.

Plastic versus elastic deformation effects on magnetic Barkhausen noise in steel

A model for magnetic flux leakage signal predictions

Investigation of the stress‐dependent magnetic easy axis in steel using magnetic Barkhausen noise

Characterization of the magnetic easy axis in pipeline steel using magnetic Barkhausen noise.