Hyperspectral imaging for detection of corrosion on intermediate level nuclear waste containers

Intermediate level nuclear waste (ILW) will be stored above ground in 304L stainless steel (SS) containers for the next 100 years. During this period, the containers need to be monitored for atmospheric pitting corrosion - a known precursor of atmospherically induced stress corrosion cracking. Hyperspectral (HS) and optical imaging of pitting corrosion products from droplet experiments have been investigated towards developing a system for long term monitoring of atmospheric pitting corrosion of stainless steel containers in ILW stores. Common corrosion products were first identified via Raman spectroscopic mapping as akaganeite (β-FeOOH) and lepidocrocite (γ-FeOOH), with a secondary presence of layered double hydroxide (green rust). HS and optical methods were then compared for their efficacy at rust detection. Whilst it was not possible to identify specific corrosion species using HS imaging, HS images of rust under pitted droplets provided better contrast with the background steel than colour photography due to species having lower absorbance the near infrared (850 nm) than red (650 nm). Finally, the relationship between rust area and pit volume was determined by comparing colour photography (rust area) with confocal laser scanning microscopy (pit volume). A good correlation was present for samples exposed to a fixed relative humidity (RH) for MgCl2 droplets and CaCl2 droplets with small pit volumes. Poor correlation was found for samples exposed to natural fluctuations in RH. It was concluded that optical methods are viable for the detection of rust, but less effective for quantification of pit volumes

Thermoelastic and photoelastic full-field stress measurement

Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA and polycarbonate.;An anisotropic electromagnetic boundary value model was developed to understand more fully the mechanisms through which photoelastic stress patterns are produced. This model produced intensity contour maps which matched the fringe patterns observed in the laboratory, and allowed the effect of measurement errors on the calculated stress tensor to be quantified. One significant source of error was the retro-reflective backing, which depolarized the light and degraded the resulting photoelastic fringes. A quantitative analysis of the degraded fringes, to be used as a rating scheme for reflective backing materials, showed that the isoclinic lines shift position as a result of the backing roughness and oblique incidence. This is a concern when calculating the stress components through the combination of photoelasticity and thermoelasticity because the data maps are integrated at the pixel level. Small shifts in the photoelastic fringes result in incorrect information being assigned to some pixels and hence lead to uncertainties in the stress tensor components. Progress in the understanding of the depolarization at the reflective backing allows the specification of new materials that will minimize this effect, as well as the development of robust computer algorithms to correct for any remaining depolarization

Thermoelastic and photoelastic full-field stress measurement

Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA and polycarbonate.;An anisotropic electromagnetic boundary value model was developed to understand more fully the mechanisms through which photoelastic stress patterns are produced. This model produced intensity contour maps which matched the fringe patterns observed in the laboratory, and allowed the effect of measurement errors on the calculated stress tensor to be quantified. One significant source of error was the retro-reflective backing, which depolarized the light and degraded the resulting photoelastic fringes. A quantitative analysis of the degraded fringes, to be used as a rating scheme for reflective backing materials, showed that the isoclinic lines shift position as a result of the backing roughness and oblique incidence. This is a concern when calculating the stress components through the combination of photoelasticity and thermoelasticity because the data maps are integrated at the pixel level. Small shifts in the photoelastic fringes result in incorrect information being assigned to some pixels and hence lead to uncertainties in the stress tensor components. Progress in the understanding of the depolarization at the reflective backing allows the specification of new materials that will minimize this effect, as well as the development of robust computer algorithms to correct for any remaining depolarization

The dispersal pattern of Thekopsora minima in wild blueberry determined by a molecular detection method

Blueberry rust caused by Thekopsora minima is a common disease in wild blueberry (Vaccinium angustifolium) and other Vaccinium genera. Understanding the spore dispersal pattern and disease cycle of fungal pathogens in wild blueberry is crucial for the development of a more efficient disease management program. Molecular assays for rapid detection and quantification of Thekopsora minima were developed to be incorporated with a spore trap sampling method and weather data collection to examine spore dispersal pattern and production in three different fields: Blueberry Hill Farm in Jonesboro, East Machias, and Spring Pond in Deblois, Maine, in three years 2014, 2015 and 2017. A total of fifteen primer sets for PCR assays and one set of six Loop-mediated isothermal amplification assay (LAMP) primers developed from the internal transcribed spacer (ITS) regions of T. minima were tested for specificity and sensitivity towards T. minima DNA. There was one primer set (TMITS2F and TMITS2GR) that was specific to rust in both PCR and qPCR assay and could detect down to about 20 copies of DNA. Lower DNA level detection (about 2 copies) is possible but often nonreproducible. The LAMP assays results were found to be not reproducible. The qPCR with the two primers TMITS2F and TMITS2GR was used to quantify rust spores in the spore trap tape DNA extracted by a Phenol-Chloroform method. Weather factors including temperature and leaf wetness duration (LWD) were collected using weather stations and button loggers placed in the fields. Calculated weekly sums of LWD and optimal temperature (17oC to 22oC) hour for uredinia production (TH) and weekly averages of other weather factors were analyzed with the weekly spore count numbers using a linear mixed model with the random effects from weeks, fields and years. There was a significant correlation between spore counts using a compound microscope and the qPCR method. There was no clear pattern of temperature, TH and LWD effects on spore numbers quantified by qPCR or microscopy. A linear mixed model (LMM) for disease severity in 2017 testing the effects of log of spore number quantified by qPCR assays, average temperature, LWD, and the random effects of weeks and fields, found that both temperature and LWD had significant negative effects on the disease severity (pT. minima. This relationship could be due to the time required for spores to germinate and cause disease. The proposed preliminary models for disease severity and weather variables, as well as the relationship between the spore number and disease severity need to be tested with data from more years and fields to confirm the results. Nevertheless, the establishment of the molecular assay and predicting models for spore number in this study could be a useful tool for future research on disease management and development of a disease warning strategy for T. minima in wild blueberry

An overview of molecular marker methods for plants

The development and use of molecular markers for the detection and exploitation of DNA polymorphism is one of the most significant developments in the field of molecular genetics. The presence of various types of molecular markers, and differences in their principles, methodologies, and applications require careful consideration in choosing one or more of such methods. No molecular markers are available yet that fulfill all requirements needed by researchers. According to the kind of study to be undertaken, one can choose among the variety of molecular techniques, each of which combines at least some desirable properties. This article provides detail review for 11 different molecular marker methods: restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), inter-simple sequencerepeats (ISSRs), sequence characterized regions (SCARs), sequence tag sites (STSs), cleaved amplified polymorphic sequences (CAPS), microsatellites or simple sequence repeats (SSRs), expressedsequence tags (ESTs), single nucleotide polymorphisms (SNPs), and diversity arrays technology (DArT)

Microstructure Characterization of As-cast, Creep-tested and Ex-service Steam-methane Reformer Tube

The main objective of this project is to study the microstructural transformation of a steam-methane reformer tube material during creep and after long term service by comparing the microstructures in creep-tested samples, ex-service samples, and as-cast samples. The creep-tested samples were not completely representative of the actual creep process during service. The ex-service material represents the material that underwent actual service condition. The as-cast and creep-tested samples were obtained from the Schmidt+Clemens (Spain) for preparation and evaluation, while the ex-service samples were obtained from a methanol plant in North America. The microstructural comparisons were made in terms of the shape, average particle size, particle area fraction and percentage. The samples were examined using optical microscope (OM) and scanning electron microscope (SEM), with secondary electron (SE) and backscattered electron (BSE) imaging. Energy dispersive spectroscopy (EDS) was conducted at selected areas of the samples. The average particle size and particle area percentage of the primary carbides were measured using NIH ImageJ software. The shape of the primary carbides (M23C6 and NbC) in the ex-service sample is rounder compared to the creep-tested and finer shape of the as-cast sample with increasing service time and temperature