Perturbation, extraction and refinement of invariant pairs for matrix polynomials

Generalizing the notion of an eigenvector, invariant subspaces are frequently used in the context of linear eigenvalue problems, leading to conceptually elegant and numerically stable formulations in applications that require the computation of several eigenvalues and/or eigenvectors. Similar benefits can be expected for polynomial eigenvalue problems, for which the concept of an invariant subspace needs to be replaced by the concept of an invariant pair. Little has been known so far about numerical aspects of such invariant pairs. The aim of this paper is to fill this gap. The behavior of invariant pairs under perturbations of the matrix polynomial is studied and a first-order perturbation expansion is given. From a computational point of view, we investigate how to best extract invariant pairs from a linearization of the matrix polynomial. Moreover, we describe efficient refinement procedures directly based on the polynomial formulation. Numerical experiments with matrix polynomials from a number of applications demonstrate the effectiveness of our extraction and refinement procedures

Should I Stay or should I Go?: The Effects of Student Individual Differences on Stress and Estimated Gains from the University Experience

The aim of this thesis was to identify factors at the commencement of university study that may enable prediction of both estimate of gains and experience of stresses. This was done in order to provide information that may enable early identification of risk factors in respect to student attrition. To this end, the thesis examined individual differences amongst students that relate to perception of both estimated gains and stress early in the university experience. Initially, the individual differences studied were those relating to student demographics of age, gender, whether the student performed additional part-time work and the number of hours of work performed and the influence of finances. This first round of testing was performed by distributing questionnaires examining the aforementioned via student welcome packs at commencement of university study. The results of this first round of testing suggested particular importance of intrinsic values on estimated gains. In addition to some influence of finances, gender and hours of work. From open questions present in this first round of testing, focus group questions were formulated in order to further develop the questionnaire. From the findings of study two, this was then expanded to include the influence of perceived demands, control and support and locus of control on estimated gains and subjective perceived stress. This was again performed by distributing a questionnaire at inception, albeit personally to help response rate and answer any queries. This third round of testing, as implied by the focus group responses, found an additional influence of locus of control and the perception of demands, control and support on estimated gains and stress. Finally, the fourth round of testing included biological indicators of stress, namely salivary cortisol levels through the use of analysis of levels of salivary cortisol, collected using a salivette. This final study suggested a difference in the effects of perceived demands, control and support on both perceived and biological responses to stress The study in all found that there is a definite prediction of estimate of gains from the university environment by the work values studied. Although it was found that gains were primarily influenced by intrinsic values (achievement, advancement, autonomy, personal development), an influence of extrinsic values (economics, prestige, social interaction) was also evident. In addition to work values, demographics of gender, age and hours of work were also found to influence differences in estimated gains and stress. None of the values studied were found to predict perceived stress, however the distinction between perceived and objective biological measures of stress was highlighted. In particular, with regard to the perception of demands, control and support from the university environment. The results of the study also suggested that the extent to which students perceive demands, control and support from the university environment may also have an impact on the student experience of stress, particularly biological stress, which can result in potential harm to physical well-being

Fatigue Alters in Vivo Function Within and Between Limb Muscles During Locomotion

Muscle fatigue, a reduction in force as a consequence of exercise, is an important factor for any animal that moves, and can result from both peripheral and/or central mechanisms. Although much is known about whole-limb force generation and activation patterns in fatigued muscles under sustained isometric contractions, little is known about the in vivo dynamics of limb muscle function in relation to whole-body fatigue. Here we show that limb kinematics and contractile function in the lateral (LG) and medial (MG) gastrocnemius of helmeted guineafowl (Numida meleagris) are significantly altered following fatiguing exercise at 2 m sK1 on an inclined treadmill. The two most significant findings were that the variation in muscle force generation, measured directly from the muscles’ tendons, increased significantly with fatigue, and fascicle shortening in the proximal MG, but not the distal MG, decreased significantly with fatigue. We suggest that the former is a potential mechanism for decreased stability associated with fatigue. The region-specific alteration of fascicle behaviour within the MG as a result of fatigue suggests a complex response to fatigue that probably depends on muscle–aponeurosis and tendon architecture not previously explored. These findings highlight the importance of studying the integrative in vivo dynamics of muscle function in response to fatigue.Organismic and Evolutionary Biolog

Mycobacterium avium subspecies paratuberculosis:human exposure through environmental and domestic aerosols

Mycobacterium avium subspecies paratuberculosis (Map) causes Johne’s disease in animals and is significantly associated with Crohn’s disease (CD) in humans. Our previous studies have shown Map to be present in U.K. rivers due to land deposition from chronic livestock infection and runoff driven by rainfall. The epidemiology of CD in Cardiff showed a significant association with the River Taff, in which Map can be detected on a regular basis. We have previously hypothesized that aerosols from the river might influence the epidemiology of CD. In this preliminary study, we detected Map by quantitative PCR in one of five aerosol samples collected above the River Taff. In addition, we examined domestic showers from different regions in the U.K. and detected Map in three out of 30 independent samples. In detecting Map in river aerosols and those from domestic showers, this is the first study to provide evidence that aerosols are an exposure route for Map to humans and may play a role in the epidemiology of CD

Dexamethasone and p38 MAPK inhibition of cytokine production from human lung fibroblasts

From Wiley via Jisc Publications RouterHistory: received 2020-08-04, rev-recd 2020-10-19, accepted 2020-11-02, pub-electronic 2020-11-14, pub-print 2021-08Article version: VoRPublication status: PublishedAbstract: Lung fibroblasts are involved in airway inflammation and remodelling in COPD. We report an investigation of the effects of combining a p38 MAPK inhibitor with a corticosteroid on cytokine production by a human lung fibroblast cell line and primary fibroblasts obtained from human lung tissue. Our main interest was to determine whether additive or synergistic anti‐inflammatory effects would be observed. We observed inhibition of IL‐6 and CXCL8 secretion from both lung fibroblast models by dexamethasone (maximal inhibition 40–90%) and the p38 MAPK inhibitor BIRB (maximal inhibition 30–60%), used alone and evidence of increased anti‐inflammatory effects when used in combination. This combination effect was more apparent for TNF‐a stimulated cytokine production (maximal inhibition increased by 10–20%). Interaction ratio analysis showed this enhanced effect to be additive rather than synergistic interaction. Similar results were obtained using both fibroblast cell culture models. Combining a p38 MAPK to corticosteroids may help reduce fibroblast mediated inflammation in COPD

Functional and architectural complexity within and between muscles: regional variation and intermuscular force transmission

Over the past 30 years, studies of single muscles have revealed complex patterns of regional variation in muscle architecture, activation, strain and force. In addition, muscles are often functionally integrated with other muscles in parallel or in series. Understanding the extent of this complexity and the interactions between muscles will profoundly influence how we think of muscles in relation to organismal function, and will allow us to address questions regarding the functional benefits (or lack thereof) and dynamics of this complexity under in vivo conditions. This paper has two main objectives. First, we present a cohesive and integrative review of regional variation in function within muscles, and discuss the functional ramifications that can stem from this variation. This involves splitting regional variation into passive and active components. Second, we assess the functional integration of muscles between different limb segments by presenting new data involving in vivo measurements of activation and strain from the medial gastrocnemius, iliotibialis cranialis and iliotibialis lateralis pars preacetabularis of the helmeted guinea fowl (Numida meleagris) during level running on a motorized treadmill. Future research directions for both of these objectives are presented.Organismic and Evolutionary Biolog