Ultrasonic metal sheet thickness measurement without prior wave speed calibration

Conventional ultrasonic mensuration of sample thickness from one side only requires the bulk wave reverberation time and a calibration speed. This speed changes with temperature, stress, and microstructure, limiting thickness measurement accuracy. Often, only one side of a sample is accessible, making in situ calibration impossible. Non-contact ultrasound can generate multiple shear horizontal guided wave modes on one side of a metal plate. Measuring propagation times of each mode at different transducer separations, allows sheet thickness to be calculated to better than 1% accuracy for sheets of at least 1.5 mm thickness, without any calibration

Can Frustration Preserve a Quasi-Two-Dimensional Spin Fluid?

Using spin-wave theory, we show that geometric frustration fails to preserve a two-dimensional spin fluid. Even though frustration can remove the interlayer coupling in the ground-state of a classical anti-ferromagnet, spin layers innevitably develop a quantum-mechanical coupling via the mechanism of ``order from disorder''. We show how the order from disorder coupling mechanism can be viewed as a result of magnon pair tunneling, a process closely analogous to pair tunneling in the Josephson effect. In the spin system, the Josephson coupling manifests itself as a a biquadratic spin coupling between layers, and for quantum spins, these coupling terms are as large as the inplane coupling. An alternative mechanism for decoupling spin layers occurs in classical XY models in which decoupled "sliding phases" of spin fluid can form in certain finely tuned conditions. Unfortunately, these finely tuned situations appear equally susceptible to the strong-coupling effects of quantum tunneling, forcing us to conclude that in general, geometric frustration cannot preserve a two-dimensional spin fluid.Comment: 12 pages, 3 figure

Facilitating Academic and Mental Health Resilience in Students with a Learning Disability

This qualitative study explored the educational journeys of five postsecondary students with learning disabilities (LD) from the perspective of the students and their families. Using a resilience lens, it examined the challenges that they faced and the capacities and resources that facilitated their resilience and helped them achieve their current level of academic achievement and mental health. A retrospective, multiple case study design was used, and a series of three interviews was conducted with each university student with an LD and their families. The participants identified a number of interactions among the students and their parents, teachers, and peers that helped shape and develop the capacities they needed in order to negotiate for the supports and resources that sustained their well-being. These capacities included an awareness and acceptance of their LD and themselves as learners, the self-advocacy skills they needed in order to seek out and negotiate for the supports and accommodations that would help them succeed, the ability to set lofty yet attainable goals, the perseverance to work toward these goals in spite of setbacks and challenges, and the willingness to use the supports and resources that were available to them

Redefining the population at risk of listeriosis in England and Wales

Listeriosis is a rare but severe food‐borne disease caused by the opportunistic, bacterial pathogen Listeria monocytogenes. The elderly, those who are immunocompromised and pregnant women and their unborn or newborn infants are disproportionately affected. Listeriosis has a high case fatality ratio (up to 44%) and is the commonest cause of death ascribed to a food‐borne pathogen in the United Kingdom (UK). The number of cases of listeriosis in England and Wales reported to the Health Protection Agency (HPA) ‐ the arms length governmental body mandated with protecting the health of the population ‐ increased from an average of 110 cases per year between 1990 and 2000 to an average of 192 cases per year between 2001 and 2009. The epidemiology of listeriosis appeared to change with the observed increase almost exclusively among non‐pregnancy related cases, aged ≥60 years presenting with bacteraemia in the absence of central nervous system infection (CNS). Given the potential severity of listeriosis and that, as a predominantly foodborne disease, these infections are largely avoidable, there was a public health imperative to investigate the observed increase. Disease presentation, concurrent conditions, medications, deprivation, diet and mortality risk factors amongst non‐pregnancy related listeriosis cases and ethnicity amongst pregnancy related cases were investigated using national surveillance data. The increased incidence of bacteraemic cases occurred in those with cancer, particularly digestive organ malignancies (Odds ratio (OR) [95% confidence interval (CI)]: 16.7 [3.8 – 73]) and, to a lesser degree, those with conditions that necessitate treatment with stomach acid inhibiting medication (3.2 [1.5 – 6.6]). Ethnicity and/or deprivation were found to be important drivers for infection. Compared to the most affluent areas, disease incidence was 38% (95% CI: 16 to 65) higher in the most deprived areas of the country. Cases were more likely than the general population to purchase foods from convenience stores (OR [95% CI]: 5.37\ud [3.53 – 8.17]) or from local services ‐ bakers (3.40 [2.39 – 4.86]), butchers (1.62 [1.11 – 2.34]), fishmongers (5.05 [3.19 – 7.99]) and greengrocers (1.92 [1.32 – 2.78]) ‐ and their risk profile changed with increasing deprivation. The proportion of pregnancy related cases classed as ethnic increased significantly from 2001 to 2008 (chi‐square test for trend; p=0.002). The increase in the proportion of pregnancy related cases that were ethnic was most marked in 2006, 2007 and 2008, when the incidence was higher than expected given the underlying population (Relative risk (RR) [95% CI]: 2.38 [1.07 – 5.29], 3.82 [1.82 – 8.03] and 4.33 [1.74 – 10.77], respectively). A wide range of underlying conditions appeared to increase the risk of infection, most notably diseases of the liver (RR [95% CI]: 22.4 [17.7 – 28.4]), systemic connective tissue disorders (18.3 [12.6 – 26.6]), neoplasms of the lymphoid, hematopioetic, and related tissues (17.6 [15.1 – 20.6]), psychoactive substance (alcohol related in 96% of reports; 12.3 [9.4 – 16.1]) and renal failure (12.2 [9.8 – 15.1]). Associated medications, including cytotoxic drugs (RR [95% CI]: 320.9 [228.5 – 450.7]), drugs affecting the immune response (18.5 [11.6 – 29.5]) and corticosteroids (11.1 [8.5 – 14.6]), and food groups, most notably smoked salmon (OR [95% CI]: 4.82 [2.99 – 7.76]), other cold cooked fish (22.32 [15.85 – 31.44]), camembert (4.80 [2.32 – 9.90]), hard cheese other than cheddar (2.37 [1.69 – 3.30]), blue cheese (2.24 [1.47 – 3.43]), also appeared to be associated with increased risk of infection. Underlying conditions, particularly malignancies of the breast (OR [95% CI]: 3.2 [1.7 – 6.2]) and respiratory and intrathoracic organs (3.9 [2.2 – 7.1]), alcoholism (2.7 [1.6 – 4.3]), cardiovascular diseases (1.4 [1.01 – 1.9]), treatment to reduce stomach acid secretion (1.6 [1.1 – 2.3])and increasing age (cases ≥80 years versus less than 60 years; 3.1 [2.3 – 4.2]) increased the risk of death amongst cases. This cohesive body of work redefines the population at risk of listeriosis and indicates that there is added value in actively targeting appropriate food safety advice at a range of vulnerable groups other than pregnant women, to whom information has previously been routinely and preferentially disseminated

The transient response of global-mean precipitation to increasing carbon dioxide levels

The transient response of global-mean precipitation to an increase in atmospheric carbon dioxide levels of 1% yr(-1) is investigated in 13 fully coupled atmosphere-ocean general circulation models (AOGCMs) and compared to a period of stabilization. During the period of stabilization, when carbon dioxide levels are held constant at twice their unperturbed level and the climate left to warm, precipitation increases at a rate of similar to 2.4% per unit of global-mean surface-air-temperature change in the AOGCMs. However, when carbon dioxide levels are increasing, precipitation increases at a smaller rate of similar to 1.5% per unit of global-mean surface-air-temperature change. This difference can be understood by decomposing the precipitation response into an increase from the response to the global surface-temperature increase (and the climate feedbacks it induces), and a fast atmospheric response to the carbon dioxide radiative forcing that acts to decrease precipitation. According to the multi-model mean, stabilizing atmospheric levels of carbon dioxide would lead to a greater rate of precipitation change per unit of global surface-temperature change

Density Functional Theory Transition-State Modeling for the Prediction of Ames Mutagenicity in 1,4 Michael Acceptors

Assessing the safety of new chemicals, without introducing the need for animal testing, is a task of great importance. The Ames test, a widely used bioassay to assess mutagenicity, can be an expensive, wasteful process with animal-derived reagents. Existing in silico methods for the prediction of Ames test results are traditionally based on chemical category formation and can lead to false positive predictions. Category formation also neglects the intrinsic chemistry associated with DNA reactivity. Activation energies and HOMO/LUMO energies for thirty 1,4 Michael acceptors were calculated using a model nucleobase and were further used to predict the Ames test result of these compounds. The proposed model builds upon existing work and examines the fundamental toxicant-target interactions using density functional theory transition-state modeling. The results show that Michael acceptors with activation energies &lt; 20.7 kcal/mol and LUMO energies &lt; -1.85 eV are likely to act as direct mutagens upon exposure to DNA.</p

Density Functional Theory Transition-State Modeling for the Prediction of Ames Mutagenicity in 1,4 Michael Acceptors

Assessing the safety of new chemicals, without introducing the need for animal testing, is a task of great importance. The Ames test, a widely used bioassay to assess mutagenicity, can be an expensive, wasteful process with animal-derived reagents. Existing in silico methods for the prediction of Ames test results are traditionally based on chemical category formation and can lead to false positive predictions. Category formation also neglects the intrinsic chemistry associated with DNA reactivity. Activation energies and HOMO/LUMO energies for thirty 1,4 Michael acceptors were calculated using a model nucleobase and were further used to predict the Ames test result of these compounds. The proposed model builds upon existing work and examines the fundamental toxicant-target interactions using density functional theory transition-state modeling. The results show that Michael acceptors with activation energies <20.7 kcal/mol and LUMO energies < -1.85 eV are likely to act as direct mutagens upon exposure to DNA