Search

Left atrial ablation to obtain pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF) is a technologically intensive procedure utilizing innovative and continually improving technology. Changes in the technology utilized for PVI can in turn lead to changes in procedure costs. Because of the proximity of the esophagus to the posterior wall of the left atrium, various technologies have been utilized to protect against thermal injury during ablation. The impact on hospital costs during PVI ablation from utilization of different technologies for esophageal protection during ablation has not previously been evaluated.To compare the costs of active esophageal cooling to luminal esophageal temperature (LET) monitoring during left atrial ablation.We performed a time-driven activity-based costing (TDABC) analysis to determine costs for PVI procedures. Published data and literature review were utilized to determine differences in procedure time and same-day discharge rates using different esophageal protection technologies, and to determine the cost impacts of same-day discharge versus overnight hospitalization after PVI procedures. The total costs were then compared between cases using active esophageal cooling to those using LET monitoring.The effect of implementing active esophageal cooling was associated with up to a 24.7% reduction in mean total procedure time, and an 18% increase in same-day discharge rate. TDABC analysis identified a $681 reduction in procedure costs associated with the use of active esophageal cooling after including the cost of the esophageal cooling device. Factoring in the 18% increase in same-day discharge resulted in an increased cost savings of $2,135 per procedure.The use of active esophageal cooling is associated with significant cost-savings when compared to traditional LET monitoring, even after accounting for the additional cost of the cooling device. These savings originate from a per-patient procedural time savings and a per-population improvement in same-day discharge rate.

Radiofrequency (RF) ablation of the left atrium of the heart is increasingly used to treat atrial fibrillation (AF). Unfortunately, inadvertent thermal injury to the esophagus can occur during this procedure, potentially creating an atrioesophageal fistula (AEF) which is 80% fatal. The ensoETM (Attune Medical, Chicago, IL), is an esophageal cooling device that has been shown to reduce thermal injury to the esophagus during RF ablation.This review summarizes growing evidence related to active esophageal cooling during RF ablation for the treatment of AF. The review presents data demonstrating improved outcomes related to patient safety and procedural efficiency and suggests directions for future research.The use of active esophageal cooling during RF ablation reduces esophageal injury, reduces or eliminates fluoroscopy requirements, reduces procedure duration and post-operative pain, and increases long-term freedom from arrhythmia. These effects in turn increase patient same-day discharge rates, decrease operator cognitive load, and reduce cost. These findings are likely to further accelerate the adoption of active esophageal cooling.Atrial fibrillation is a condition in which the heart beats irregularly, causing symptoms such as palpitations, dizziness, shortness of breath, and chest pain. Atrial fibrillation increases the risk of stroke, heart failure, dementia, and death. One treatment for atrial fibrillation is a procedure called a catheter ablation. This procedure is minimally invasive and is performed by a specialized cardiologist, called an electrophysiologist. The electrophysiologist, or operator, uses an energy source, such as radiofrequency energy (radio waves), to stop erratic electrical signals from traveling through the heart. One complication of the catheter ablation is an inadvertent injury to the esophagus, the organ that passes food from the mouth to the stomach. If the injury is severe, it may develop into an atrioesophageal fistula, which often results in death. In this review, a new technology is described that helps prevent this type of injury and can provide additional benefits for the patient, operator, and hospital.

Objectives We characterized real-time patient portal test result viewing among emergency department (ED) patients and described patient characteristics overall and among those not enrolled in the portal at ED arrival. Methods Our observational study at an academic ED used portal log data to trend the proportion of adult patients who viewed results during their visit from May 04, 2021 to April 04, 2022. Correlation was assessed visually and with Kendall's τ. Covariate analysis using binary logistic regression assessed result(s) viewed as a function of time accounting for age, sex, ethnicity, race, language, insurance status, disposition, and social vulnerability index (SVI). A second model only included patients not enrolled in the portal at arrival. We used random forest imputation to account for missingness and Huber-White heteroskedasticity-robust standard errors for patients with multiple encounters (α = 0.05). Results There were 60,314 ED encounters (31,164 unique patients). In 7,377 (12.2%) encounters, patients viewed results while still in the ED. Patients were not enrolled for portal use at arrival in 21,158 (35.2%) encounters, and 927 (4.4% of not enrolled, 1.5% overall) subsequently enrolled and viewed results in the ED. Visual inspection suggests an increasing proportion of patients who viewed results from roughly 5 to 15% over the study (Kendall's τ = 0.61 [p Conclusion We observed increased portal-based test result viewing among ED patients over the year since the 21st Century Cures act went into effect, even among those not enrolled at arrival. We observed disparities in those who viewed results.

Long-term sequelae after symptomatic SARS-CoV-2 infection may impact well-being, yet existing data primarily focus on discrete symptoms and/or health care use.To compare patient-reported outcomes of physical, mental, and social well-being among adults with symptomatic illness who received a positive vs negative test result for SARS-CoV-2 infection.This cohort study was a planned interim analysis of an ongoing multicenter prospective longitudinal registry study (the Innovative Support for Patients With SARS-CoV-2 Infections Registry [INSPIRE]). Participants were enrolled from December 11, 2020, to September 10, 2021, and comprised adults (aged ≥18 years) with acute symptoms suggestive of SARS-CoV-2 infection at the time of receipt of a SARS-CoV-2 test approved by the US Food and Drug Administration. The analysis included the first 1000 participants who completed baseline and 3-month follow-up surveys consisting of questions from the 29-item Patient-Reported Outcomes Measurement Information System (PROMIS-29; 7 subscales, including physical function, anxiety, depression, fatigue, social participation, sleep disturbance, and pain interference) and the PROMIS Short Form-Cognitive Function 8a scale, for which population-normed T scores were reported.SARS-CoV-2 status (positive or negative test result) at enrollment.Mean PROMIS scores for participants with positive COVID-19 tests vs negative COVID-19 tests were compared descriptively and using multivariable regression analysis.Among 1000 participants, 722 (72.2%) received a positive COVID-19 result and 278 (27.8%) received a negative result; 406 of 998 participants (40.7%) were aged 18 to 34 years, 644 of 972 (66.3%) were female, 833 of 984 (84.7%) were non-Hispanic, and 685 of 974 (70.3%) were White. A total of 282 of 712 participants (39.6%) in the COVID-19-positive group and 147 of 275 participants (53.5%) in the COVID-19-negative group reported persistently poor physical, mental, or social well-being at 3-month follow-up. After adjustment, improvements in well-being were statistically and clinically greater for participants in the COVID-19-positive group vs the COVID-19-negative group only for social participation (β = 3.32; 95% CI, 1.84-4.80; P .001); changes in other well-being domains were not clinically different between groups. Improvements in well-being in the COVID-19-positive group were concentrated among participants aged 18 to 34 years (eg, social participation: β = 3.90; 95% CI, 1.75-6.05; P .001) and those who presented for COVID-19 testing in an ambulatory setting (eg, social participation: β = 4.16; 95% CI, 2.12-6.20; P .001).In this study, participants in both the COVID-19-positive and COVID-19-negative groups reported persistently poor physical, mental, or social well-being at 3-month follow-up. Although some individuals had clinically meaningful improvements over time, many reported moderate to severe impairments in well-being 3 months later. These results highlight the importance of including a control group of participants with negative COVID-19 results for comparison when examining the sequelae of COVID-19.

Background Frogeye leaf spot is a disease of soybean, and there are limited sources of crop genetic resistance. Accurate quantification of resistance is necessary for the discovery of novel resistance sources, which can be accelerated by using a low-cost and easy-to-use image analysis system to phenotype the disease. The objective herein was to develop an automated image analysis phenotyping pipeline to measure and count frogeye leaf spot lesions on soybean leaves with high precision and resolution while ensuring data integrity. Results The image analysis program developed measures two traits: the percent of diseased leaf area and the number of lesions on a leaf. Percent of diseased leaf area is calculated by dividing the number of diseased pixels by the total number of leaf pixels, which are segmented through a series of color space transformations and pixel value thresholding. Lesion number is determined by counting the number of objects remaining in the image when the lesions are segmented. Automated measurement of the percent of diseased leaf area deviates from the manually measured value by less than 0.05% on average. Automatic lesion counting deviates by an average of 1.6 lesions from the manually counted value. The proposed method is highly correlated with a conventional method using a 1–5 ordinal scale based on a standard area diagram. Input image compression was optimal at a resolution of 1500 × 1000 pixels. At this resolution, the image analysis method proposed can process an image in less than 10 s and is highly concordant with uncompressed images. Conclusion Image analysis provides improved resolution over conventional methods of frogeye leaf spot disease phenotyping. This method can improve the precision and resolution of phenotyping frogeye leaf spot, which can be used in genetic mapping to identify QTLs for crop genetic resistance and in breeding efforts for resistance to the disease.

Frogeye leaf spot, caused by the fungus Cercospora sojina, is a threat to soybeans in the southeastern and midwestern United States that can be controlled by crop genetic resistance. Limited genetic resistance to the disease has been reported, and only three sources of resistance have been used in modern soybean breeding. To discover novel sources and identify the genomic locations of resistance that could be used in soybean breeding, a GWAS was conducted using a panel of 329 soybean accessions selected to maximize genetic diversity. Accessions were phenotyped using a 1-5 visual rating and by using image analysis to count lesion number and measure the percent of leaf area diseased. Eight novel loci on eight chromosomes were identified for three traits utilizing the FarmCPU or BLINK models, of which a locus on chromosome 11 was highly significant across all model-trait combinations. KASP markers were designed using the SoySNP50K Beadchip and variant information from 65 of the accessions that have been sequenced to target SNPs in the gene model Glyma.11g230400, a LEUCINE-RICH REPEAT RECEPTOR-LIKE PROTEIN KINASE. The association of a KASP marker, GSM990, designed to detect a missense mutation in the gene was the most significant with all three traits in a genome-wide association, and the marker may be useful to select for resistance to frogeye leaf spot in soybean breeding.

The 21st century has seen an enormous growth in emergency medical services (EMS) information technology systems, with corresponding accumulation of large volumes of data. Despite this growth, integration efforts between EMS-based systems and electronic health records, and public-sector databases have been limited due to inconsistent data structure, data missingness, and policy and regulatory obstacles. Efforts to integrate EMS systems have benefited from the evolving science of entity resolution and record linkage. In this chapter, we present the history and fundamentals of record linkage techniques, an overview of past uses of this technology in EMS, and a look into the future of record linkage techniques for integrating EMS data systems including the use of machine learning-based techniques.

Key message Eight soybean genomic regions, including six never before reported, were found to be associated with resistance to soybean rust (Phakopsora pachyrhizi) in the southeastern USA. Abstract Soybean rust caused by Phakopsora pachyrhizi is one of the most important foliar diseases of soybean [Glycine max (L.) Merr.]. Although seven Rpp resistance gene loci have been reported, extensive pathotype variation in and among fungal populations increases the importance of identifying additional genes and loci associated with rust resistance. One hundred and ninety-one soybean plant introductions from Japan, Indonesia and Vietnam, and 65 plant introductions from other countries were screened for resistance to P. pachyrhizi under field conditions in the southeastern USA between 2008 and 2015. The results indicated that 84, 69, and 49% of the accessions from southern Japan, Vietnam or central Indonesia, respectively, had negative BLUP values, indicating less disease than the panel mean. A genome-wide association analysis using SoySNP50K Infinium BeadChip data identified eight genomic regions on seven chromosomes associated with SBR resistance, including previously unreported regions of Chromosomes 1, 4, 6, 9, 13, and 15, in addition to the locations of the Rpp3 and Rpp6 loci. The six unreported genomic regions might contain novel Rpp loci. The identification of additional sources of rust resistance and associated genomic regions will further efforts to develop soybean cultivars with broad and durable resistance to soybean rust in the southern USA.

Fine mapping quantitative trait loci (QTL) and understanding the molecular mechanism and underlying functions of genes are vital to the advancement of plant research and plant breeding. Target region sequencing (TRS) provides an efficient way to assist in accomplishing these goals. Once a genomic region is found to be responsible for a phenotype, TRS can be deployed to characterize that region. Understanding the available methodologies to perform TRS will be advantageous when determining how to proceed with specific projects. In this article, we reviewed and summarized four main methods that are being used for TRS in plants, including hybrid capture, PCR-based enrichment, DNA fragment circularization, and RNA capture. We also discussed the potential uses of these technologies in plant research, especially the marker discovery for breeding selection. The TRS techniques outlined in this review have the potential to become commonplace in plant research, thereby having a large impact.

Aerogels are attracting increasing interest due to their functional properties, such as lightweight and high porosity, which make them promising materials for energy storage and advanced composites. Compressive deformation allows the nano- and microstructure of lamellar freeze-cast aerogels to be tailored toward the aforementioned applications, where a 3D nanostructure of closely spaced, aligned sheets is desired. Quantitatively characterizing their microstructural evolution during compression is needed to allow optimization of manufacturing, understand in-service structural changes, and determine how aerogel structure relates to functional properties. Herein we have developed methods to quantitatively analyze lamellar aerogel domains, sheet spacing, and sheet orientation in 3D and to track their evolution as a function of increasing compression through synchrotron phase contrast X-ray microcomputed tomography (μCT). The as-cast domains are predominantly aligned with the freezing direction with random orientation in the orthogonal plane. Generally the sheets rotate toward flat and their spacing narrows progressively with increasing compression with negligible lateral strain (zero Poisson's ratio). This is with the exception of sheets close to parallel with the loading direction (

Aerogels are attracting increasing interest due to their functional properties, such as light-weight and high porosity, which make them promising materials for energy storage and advanced composites. Compressive deformation allows the nano- and micro- structure of lamellar freeze-cast aerogels to be tailored towards the aforementioned applications, where a 3D nanostructure of closely spaced, aligned sheets is desired. Quantitatively characterising their microstructural evolution during compression is needed to allow optimisation of manufacturing, understand in-service structural changes, and determine how aerogel structure relates to functional properties. Herein we have developed methods to quantitatively analyse lamellar aerogel domains, sheet spacing and sheet orientation in 3D and to track their evolution as a function of increasing compression through synchrotron phase contrast X-ray micro computed tomography (μCT). The as-cast domains are predominantly aligned with the freezing direction with random orientation in the orthogonal plane. Generally the sheets rotate towards flat and their spacing narrows progressively with increasing compression with negligible lateral strain (zero Poisson’s ratio). This is with the exception of sheets close to parallel with the loading direction (Z), which maintain their orientation and sheet spacing until ~60% compression, beyond which they exhibit buckling. These data suggest that a single-domain, fully aligned as-cast aerogel is not necessary to produce a post-compression aligned lamellar structure and indicate how the spacing can be tailored as a function of compressive strain. The analysis methods presented herein are applicable to optimising freeze-casting process and quantifying lamellar micro-domain structures generally.

ImportanceThe 21st Century Cures Act Final Rule mandates the immediate electronic availability of test results to patients, likely empowering them to better manage their health. Concerns remain about unintended effects of releasing abnormal test results to patients.ObjectiveTo assess patient and caregiver attitudes and preferences related to receiving immediately released test results through an online patient portal.Design, Setting, and ParticipantsThis large, multisite survey study was conducted at 4 geographically distributed academic medical centers in the US using an instrument adapted from validated surveys. The survey was delivered in May 2022 to adult patients and care partners who had accessed test results via an online patient portal account between April 5, 2021, and April 4, 2022.ExposuresAccess to test results via a patient portal between April 5, 2021, and April 4, 2022.Main Outcomes and MeasuresResponses to questions related to demographics, test type and result, reaction to result, notification experience and future preferences, and effect on health and well-being were aggregated. To evaluate characteristics associated with patient worry, logistic regression and pooled random-effects models were used to assess level of worry as a function of whether test results were perceived by patients as normal or not normal and whether patients were precounseled.ResultsOf 43 380 surveys delivered, there were 8139 respondents (18.8%). Most respondents were female (5129 [63.0%]) and spoke English as their primary language (7690 [94.5%]). The median age was 64 years (IQR, 50-72 years). Most respondents (7520 of 7859 [95.7%]), including 2337 of 2453 individuals (95.3%) who received nonnormal results, preferred to immediately receive test results through the portal. Few respondents (411 of 5473 [7.5%]) reported that reviewing results before they were contacted by a health care practitioner increased worry, though increased worry was more common among respondents who received abnormal results (403 of 2442 [16.5%]) than those whose results were normal (294 of 5918 [5.0%]). The result of the pooled model for worry as a function of test result normality was statistically significant (odds ratio [OR], 2.71; 99% CI, 1.96-3.74), suggesting an association between worry and nonnormal results. The result of the pooled model evaluating the association between worry and precounseling was not significant (OR, 0.70; 99% CI, 0.31-1.59).Conclusions and RelevanceIn this multisite survey study of patient attitudes and preferences toward receiving immediately released test results via a patient portal, most respondents preferred to receive test results via the patient portal despite viewing results prior to discussion with a health care professional. This preference persisted among patients with nonnormal results.

The damage mechanisms and load redistribution taking place under high temperature (350 °C), high cycle fatigue (HCF) of TC17 titanium alloy/unidirectional SiC fibre composites have been investigated in situ using synchrotron X-ray computed tomography (CT) and X-ray diffraction (XRD) under two stress amplitudes. The three-dimensional morphology of the fatigue crack and fibre fractures has been mapped by CT. At low stress amplitude, stable growth occurs with the matrix crack deflecting by 50-100 µm in height as it bypasses the bridging fibres. At higher stress amplitude, loading to the peak stress led to a burst of fibre fractures giving rise to rapid crack growth. Many of the fibre fractures occurred 50-300 µm above/below the matrix crack plane during rapid growth, contrary to that in the stable growth stage, leading to extensive fibre pull-out on the fracture surface. The changes in fibre loading, interfacial stress, and the extent of fibre-matrix debonding in the vicinity of the crack have been mapped over the fatigue cycle and after the rapid crack growth by XRD. The fibre/matrix interfacial sliding extends up to 600 µm (in the stable-growth zone) or 700 µm (in the rapid-growth zone) either side of the crack plane. The direction of interfacial shear stress reverses over the loading cycle, with the maximum frictional sliding stress reaching ~55 MPa in both regimes. In accordance with previous studies, it is possible that a degradation in fibre strength at elevated temperature is responsible for bursts of fibre fracture and rapid crack growth under higher stress amplitude.

A fundamental understanding of the behaviour of polycrystalline materials, including pharmaceuticals, is vital for control of their physicochemical and crystalline properties, which in turn has the potential to improve drug product development for example. In this work, attenuation X-ray Computed Tomography (CT) and Diffraction Contrast Tomography (DCT) are combined with molecular modelling to understand the powder packing behaviour and crystal interactions of the organic cubic compound hexamine (hexamethylenetetramine). It is the first application of DCT to polycrystalline organic materials. The crystal morphology is predicted through synthonic modelling, with fully 3D-resolved confirmation of the crystallography of the external {110} facets, edges and corner directions through DCT. Analysis of the powder-bed reveals agglomerate structures and orientational texture, with its chemical origins energetically predicted to be face-to-face in accordance with the experimental data. Finally, measurements of crystal & crystallite interactions provide evidence for different mechanisms of powder bed agglomeration.

A quality translation is a translation that has three characteristics, namely accuracy, readability, and acceptability. Assessment of the accuracy of the transfer of source language text messages into the target language should not be carried out by the researcher alone. To produce a more objective assessment, researchers need to involve other people who have competence and expertise in the field of translation. It should be noted here that an assessment of the accuracy of message redirection will always involve the source language text and the target language text. In other words, the comparison between the source language text message and the target language text message is one of the important features of assessing the accuracy of the message forwarding.

Three-dimensional (3D) characterisation and modelling of cracking in concrete have been always of great importance and interest in civil engineering. In this study, an in situ microscale X-ray computed tomography (XCT) test was carried out to characterise the 3D microscale structure and cracking behaviour under progressive uniaxial compressive loading. The 3D cracking and fracture behaviour including internal crack opening, closing, and bridging were observed through both 2D tomography slices and 3D CT images. Spatial distributions of voids and cracks were obtained to understand the overall cracking process within the specimen. Furthermore, the XCT images of the original configuration of the specimen were processed and used to build microscale realistic 3D finite element (FE) models. Cohesive interface elements were inserted into the FE mesh to capture complicated discrete crack initiation and propagation. An FE simulation of uniaxial compression was conducted and validated by the in situ XCT compression test results, followed by a tension simulation using the same image-based model to investigate the cracking behaviour. The quantitative agreement between the FE simulation and experiment demonstrates that it is a very promising and effective technique to investigate the internal damage and fracture behaviour in multiphasic composites by combining the in situ micro XCT experiment and image-based FE modelling.

The autonomous crack-healing capability of Cr 2 AlC MAX phase ceramic by surface oxidation at elevated temperatures has a huge potential for high temperature structural and protective coating applications. In this work we use time-lapse X-ray computed tomography (CT) to track the fine details of local crack filling phenomena in 3 dimensions (3D) with time. The maximum crack width that could be fully healed upon exposure to 1200 °C in air is 4.8 μm in 4 h and 10 μm after 12 h. Furthermore, during healing Cr 7 C 3 phase is observed beneath the dense Al 2 O 3 layer (average thickness of 1 μm on each crack surface) when the crack width exceeds 2 μm. The 3D image sequences indicated that the rate of healing is essentially independent of position along, or across, the crack faces. The crack healing kinetics of Cr 2 AlC at 1200 °C broadly follows a parabolic rate law with a rate constant of 4.6 × 10 −4 μm 2 s −1 . The microstructure, composition and thickness of the oxide scale in the healed crack area are characterized via post mortem SEM-EDS measurements and confirm the formation of an initial dense alumina layer on top of which a more porous layer forms. Impurity Cr particles appear to accelerate the oxidation process locally and correlative SEM imaging of the same region suggests this is by providing Cr 2 O 3 nucleation sites.

In-situ micro X-ray Computed Tomography (XCT) tests of concrete cubes under progressive compressive loading were carried out to study 3D fracture evolution. Both direct segmentation of the tomography and digital volume correlation (DVC) mapping of the displacement field were used to characterise the fracture evolution. Realistic XCT-image based finite element (FE) models under periodic boundaries were built for asymptotic homogenisation of elastic properties of the concrete cube with Young's moduli of cement and aggregates measured by micro-indentation tests. It is found that the elastic moduli obtained from the DVC analysis and the FE homogenisation are comparable and both within the Reuss-Voigt theoretical bounds, and these advanced techniques (in-situ XCT, DVC, micro-indentation and image-based simulations) offer highly-accurate, complementary functionalities for both qualitative understanding of complex 3D damage and fracture evolution and quantitative evaluation of key material properties of concrete.

Samples of SA508 grade 3 nuclear pressure vessel ferritic steel were subjected to tensile straining whilst simultaneously imaged in 3D in real time using high resolution, high frame rate time-lapse synchrotron computed tomography (CT). This enabled direct observation of void development from nucleation, through growth to coalescence and final failure validating many inferences made post mortem or by theoretical models, as well as raising new points. The sparse, large inclusions were found to nucleate voids at essentially zero plastic strain (consistent with zero interfacial strength); these became increasingly elongated with straining. In contrast, a high density of small spherical voids were found to nucleate from the sub-micron cementite particles at larger strains (>200%) only in the centre of the necked (high triaxiality) region. An interfacial strength approaching 2100MPa was inferred and soon after their nucleation, these small voids coalesce to form internal microcracks that lead to the final failure of the specimen. Perhaps surprisingly, under these conditions of generally low triaxial constraint the large voids are simply cut across and appear to play no significant role in determining the final failure. The implications of these results are discussed in terms of ductile fracture behaviour and the Gurson model for ductile fracture.

The ability to accurately map crystal grain morphology and grain boundaries in polycrystalline materials, non-destructively and in three-dimensions is required for detailed investigations into many aspects of polycrystalline deformation, as well as many other properties. Previously, the laboratory-based X-ray diffraction contrast tomography technique (LabDCT) has been shown to be capable of reconstructing crystallographic orientations and grain centres in 3D. Here we demonstrate the extension of the method to the reconstruction of the individual 3D grain shapes. Firstly, the grain boundaries are mapped by DCT in a beta‑titanium alloy (Ti-β21S) sample and validated by independent measurements of the grain shapes obtained from phase contrast tomography. The independent validation measurements show that the boundaries can be located with a mean accuracy of 4.4 μm. Secondly, the grain locations and orientations in a copper powder sample sintered at 1050 °C are tracked over time in a time-lapse manner by LabDCT and then the final state compared and validated against destructive serial sectioning EBSD (3D-EBSD) post-mortem. In this case we are able to follow the recrystallisation and competitive grain growth over time, by visualising the migration of selected grain boundaries. In particular the shrinkage and dissolution of grains in the immediate vicinity of a fast-growing grain are observed and quantified in the light of changes in misorientation relationships with the growing grain. More generally, LabDCT can be used to characterise, track or establish realistic 3D image-based models of polycrystalline microstructures across a range of crystal structures.

This study aims at understanding the constitutive relation and critical condition for the shock compression of cellular solids. A 2D virtual foam is constructed from the cross-section of a closed-cell aluminium foam imaged by micro X-ray computed tomography, which enables the realistic consideration of meso-scale structural effect in numerical modelling. Quasi-static and shock compressions of the 2D foam are simulated. A series of Hugoniot relations between shock speed (and other mechanical quantities) and impact speed are determined from the finite element (FE) simulations. It is found that the shock speed increases approximately linearly with impact speed, similar to that observed for condensed solids, but the related material constants for cellular solids have different physical implications, whereas the shock strain, stress and energy increase with impact speed nonlinearly, due to shock-enhanced cell compaction and cell-wall plastic deformation. Based on conservation laws in continuum mechanics, other Hugoniot relations are derived from the basic linear one, which agree well with those obtained from the FE simulations. It is thus demonstrated that the unique linear Hugoniot relation can be used to characterise the shock constitutive behaviour which is distinct from the quasi-static one. Furthermore, a new analytical method based on the linear Hugoniot relation is proposed to estimate the critical impact speed for shock initiation, which has reasonable agreement with the present FE simulations and previous experimental and numerical results, and outperforms the existing methods.

A variable volume flow cell has been integrated with state-of-the-art ultra-high-speed synchrotron X-ray tomography imaging. The combination allows the first real-time (sub-second) capture of dynamic pore (micron)-scale fluid transport processes in 4-D (3-D + time). With 3-D data volumes acquired at up to 20 Hz, we perform in situ experiments that capture high-frequency pore-scale dynamics in 5–25 mm diameter samples with voxel (3-D equivalent of a pixel) resolutions of 2.5 to 3.8 µm. The data are free from motion artefacts and can be spatially registered or collected in the same orientation, making them suitable for detailed quantitative analysis of the dynamic fluid distribution pathways and processes. The methods presented here are capable of capturing a wide range of high-frequency nonequilibrium pore-scale processes including wetting, dilution, mixing, and reaction phenomena, without sacrificing significant spatial resolution. As well as fast streaming (continuous acquisition) at 20 Hz, they also allow larger-scale and longer-term experimental runs to be sampled intermittently at lower frequency (time-lapse imaging), benefiting from fast image acquisition rates to prevent motion blur in highly dynamic systems. This marks a major technical breakthrough for quantification of high-frequency pore-scale processes: processes that are critical for developing and validating more accurate multiscale flow models through spatially and temporally heterogeneous pore networks.

Three-dimensional (3D) finite element models based on computed tomography (CT) images are developed to investigate the strain-rate effect on the compressive behaviour of closed-cell aluminium foam (Alporas). It is found that at strain-rates below shock conditions the rate dependence of the cell–wall material is the main cause of the strain-rate hardening of the compressive strength of Alporas foam. The foam exhibits slightly higher strain-rate sensitivity than that of the cell–wall material due to localised strain-rate amplification in some critical load-bearing elements. By contrast, the micro inertia of individual cell walls associated with the nonuniform deformation of Alporas foam has a negligible contribution. Under shock conditions the stress measured at the loading end is always enhanced, but the stress measured at the supporting end is complicated, depending on the characteristics of the contiguous cells. In general, shock leads to a concentrated large deformation in the cells at the loading end, but a restrained small deformation in the cells at the supporting end. Consequently, the hardening effect of the rate dependence of cell–wall material on the supporting stress becomes constrained with further increasing strain-rate, and the supporting compressive strength is limited to the quasi-static level when the cell–wall material is rate-independent. Keywords: Cellular materials, Compressive properties, Strain-rate sensitivity, X-ray tomography, Finite element modelling

Pitting corrosion kinetics of type 304L stainless steel have been obtained using a quasi in-situ X-ray computed tomography (X-ray CT) approach. A miniature electro-chemical cell was constructed to allow imaging during potentio-dynamic polarization of a wire specimen. The formation of three discrete pits was observed, allowing comparison between real pit geometry and different geometrical assumptions to estimate pit growth kinetics. The pit volumes obtained by X-ray CT showed good fit with the volume of metal dissolution calculated using Faraday’s law. Large fluctuations of the mean current density were observed during the pit nucleation stage, followed by pit growth with mean current densities of 1–3 A.cm−2. Stability products associated with these pits were on the order of 0.3–0.6 A.m-1, with diffusivity parameter (D.C) of 1.68–3.04 × 10−8 mol.cm−1.s −1. Diffusion coefficientsfor stable pit growth of 0.83–0.96 × 10−5 cm2.s−1 were estimated for metal ion concentrations of 4.2 M.

Corrosion rates of strained grade UNS S32202 (2202) and UNS S32205 (2205) duplex stainless steel wires have been measured, in situ, using time-lapse X-ray computed tomography. Exposures to chloride-containing (MgCl2) atmospheric environments at 50 °C (12–15 M Cl− and pH ~5) with different mechanical elastic and elastic/plastic loads were carried out over a period of 21 months. The corrosion rates for grade 2202 increased over time, showing selective dissolution with shallow corrosion sites, coalescing along the surface of the wire. Corrosion rates of grade 2205 decreased over time, showing both selective and pitting corrosion with more localised attack, growing preferentially in depth. The nucleation of stress corrosion cracking was observed in both wires. The corrosion of two grades of stainless steel has been studied, in situ, under atmospheric exposure conditions. Grade ‘2205’ duplex stainless steel (DSS) has been suggested as a possible container material for the storage of intermediate-level radioactive nuclear waste in the UK because of its high resistance to corrosion and stress corrosion cracking (SCC). Now a team led by D. Engelberg from The University of Manchester, United Kingdom, have used time-lapse X-ray computed tomography to determine the corrosion rates of strained grade ‘2202’ and ‘2205’ DSS wires—over the course of 21 months—that had been exposed to a chloride-containing thin-film electrolyte. They saw that although the corrosion rate of grade 2202 DSS wires increased with time, the corrosion rate for grade 2205 decreased, confirming its superior corrosion resistance. They also observed the nucleation of SCC cracks in both grades of wire and demonstrated that duplex stainless steels can suffer from low-temperature SCC.

Sparsity regularization (SR) such as total variation (TV) minimization allows accurate image reconstruction in x-ray computed tomography (CT) from fewer projections than analytical methods. Exactly how few projections suffice and how this number may depend on the image remain poorly understood. Compressive sensing connects the critical number of projections to the image sparsity, but does not cover CT, however empirical results suggest a similar connection. The present work establishes for real CT data a connection between gradient sparsity and the sufficient number of projections for accurate TV-regularized reconstruction. A collection of 48 x-ray CT datasets called SparseBeads was designed for benchmarking SR reconstruction algorithms. Beadpacks comprising glass beads of five different sizes as well as mixtures were scanned in a micro-CT scanner to provide structured datasets with variable image sparsity levels, number of projections and noise levels to allow the systematic assessment of parameters affecting performance of SR reconstruction algorithms6. Using the SparseBeads data, TV-regularized reconstruction quality was assessed as a function of numbers of projections and gradient sparsity. The critical number of projections for satisfactory TV-regularized reconstruction increased almost linearly with the gradient sparsity. This establishes a quantitative guideline from which one may predict how few projections to acquire based on expected sample sparsity level as an aid in planning of dose- or time-critical experiments. The results are expected to hold for samples of similar characteristics, i.e. consisting of few, distinct phases with relatively simple structure. Such cases are plentiful in porous media, composite materials, foams, as well as non-destructive testing and metrology. For samples of other characteristics the proposed methodology may be used to investigate similar relations.

There is a growing need to develop effective interaction methods that enable a single operator to manage a team of multiple robots. This paper presents a novel approach that involves treating the team as a moldable volume, in which deformations of the volume correspond to changes in team shape. The team possesses a level of autonomy that allows the team to travel to and surround buildings of interest in a patrol and cordon scenario. During surround mode, the operator explores or manipulates the team shape to create desired formations around a building. A spacing interaction method also allows the operator to adjust how robots are spaced within the current shape. Separate haptic feedback is developed for each method to allow the operator to "feel" the shape or spacing manipulation. During travel mode, the operator chooses desired travel locations and receives feedback to help identify how and where the team travels. Results from a user study suggest that haptic feedback significantly improves operator performance in a reconnaissance task when task demand is higher, but may slightly increase operator workload. In the context of the experimental setup, these results suggest that haptic feedback may contribute to heads-up control of a team of autonomous robots. There were no significant differences in levels of situation awareness due to haptic feedback in this study.

The non-invasive measurement of in-material states of stress and strain within loaded targets is a paradigm that has yet to be fully achieved. However great advances have been made using manganin sensors to achieve this goal. The gauge element for measuring the lateral stress component was redesigned from a grid configuration to a T shaped wire or foil and further the flow around the gauge was investigated by several workers numerically and experimentally and shown to be stable and tracking changes in state faithfully. Finally a staged refinement of the analysis used to deconvolve the change in resistance back to stress has given a device now fit for use as a fiducial over the range of stresses up to the weak shock limit where homogeneous and hydrodynamic behaviour ensue. This work brings together latest refinements in gauge use with comparisons with other techniques. One of these concerns the tracking of elastic-plastic transitions in target materials due to the rapid gauge response. In particular we show broad agreement with the analysis of material strength using the deconvolution due to Asay and Lipkin and attempt to reconcile the two techniques here.

Optimising the manufacture, and ultimately the mechanical performance, of powder-processed components requires an understanding of how the state of the material evolves during processing and in particular during the final sintering stage. Synchrotron X-ray microtomography has been employed to follow in situ the evolution of particle microstructure during sintering of copper powder. In particular, three-dimensional digital volume correlation of a time-lapse computed tomography image sequence allows accurate quantification of the three-dimensional movements of the particles and thereby local strain for the first time. Strains are quantified both at a coarse scale across the whole powder assembly and at higher magnification for a smaller local region of interest. Unsurprisingly, the rate of shrinkage is observed to decrease with sintering time in accordance with changes in the overall density. Heterogeneities in straining within the body are observed at the several particle level, often associated with anisotropic shrinkage in part associated with non-uniform movement and densification of small aggregates of particles between which significant changes in shrinkage are observed. These differences in shrinkage could be responsible for cracking on further densification.

Network models of porous media are beneficial for predicting the evolution of macroscopic mass transport properties. This work proposes a novel bi-regular network model based on truncated octahedral support. With the model, pore systems with different pore coordination spectra for a given average coordination number can be constructed to match experimental data. This feature and the maximum allowed pore coordination of 14 make the proposed model more realistic and flexible than the existing models based on cubic supports. Limestone is used as a study material to illustrate the model performance. Experimental pore space data for this material obtained by X-ray tomography (CT) are used for constructing microstructure-informed model realisations. It is demonstrated that with these realisations the experimentally measured permeability of the material can be predicted. The model is further used to assess the effects of pore connectivity and porosity on the permeability. It is shown that the effect of pore connectivity is substantially stronger than the effect of porosity. A strategy for calculating the evolution of permeability with damage-related pore space changes is also described. The results reveal the effects of the mechanical properties of the medium on the permeability evolution as a function of damage evolution. Developments of this strategy are suggested for deriving mechanism-based constitutive laws for engineering applications.

A rich collection of exceptionally preserved Lower Triassic fossil fish remains obtained during the Polish Spitsbergen Expedition of 2005 includes many isolated teeth be− lieved to belong to a saurichthyid actinopterygian. Stable isotope analysis (δ13C and δ18O) of putative Saurichthys teeth from the Hornsund area (South Spitsbergen) acting as a paleoenvironmental proxy has permitted trophic−level reconstruction and comparison with other Lower Triassic fish teeth from the same location. The broader range of δ13C values ob− tained for durophagous teeth of the hybodont selachian, Lissodus, probably reflects its mi− gratory behaviour and perhaps a greater feeding diversity. X−ray microcomputed tomogra− phy (XMT), a non−destructive technique, is used for the first time in order to elucidate de− tails of tooth histology, the results of which suggest that the method has considerable poten− tial as a future analytical tool.