A theoretical study of left ventricular and heart muscle dynamics

The characteristics of the left ventricle of the human heart considered as a pump have been extensively analysed. Using a new approach relying heavily on the Tensor Calculus, a theoretical model describing the mechanical and dynamical operation of the left ventricle has been developed. This has considerably greater versatility than previously proposed models. In particular the physiological shape, both under normal as well as many abnormal situations, is realistically simulated. Further, the mechanical behaviour of the ventricular wall is synthesised from anatomical data concerning the cardiac muscle fibre structure of the wall. Its mechanical and dynamical properties are then, as in the physiological situation, dependent on those of the muscle fibre. These fibre properties have also been fully investigated and a simple new model for cardiac muscle dynamics, incorporating active state, proposed. This description of the ventricular behaviour in terms of muscle properties represents the first logically structured link between cardiac muscle fibre characteristics and ventricular performance

An Interview Study of Beliefs About Confidentiality and Attitudes Towards Disclosure of Moral Injury in the Canadian Armed Forces

Military members often encounter potentially morally injurious events (PMIEs) during their service. These encounters can put them at higher risk for developing moral injury, defined as the psychological distress following morally-transgressive situations. If untreated, this can lead to negative health outcomes like depression, suicide ideation, and post-traumatic stress disorder. However, the rate of help-seeking among military members experiencing mental health issues is low. Thematic analysis was used to evaluate barriers to mental health help-seeking among individuals with CAF experience, including perceived confidentiality of information, and whether PMIEs impact the decision-making process. The sample consisted of 9 individuals with CAF experience aged 26 to 64 years (M = 48.65, SD = 10.01; 1 woman, 8 men). The results of this study indicate that military personnel are not always comfortable sharing information with health care providers. Results should aid policymakers in creating programs to help facilitate help-seeking and utilization in the military

Exploring the Metabolic Landscape of AML: From Haematopoietic Stem Cells to Myeloblasts and Leukaemic Stem Cells

Despite intensive chemotherapy regimens, up to 60% of adults with acute myeloid leukaemia (AML) will relapse and eventually succumb to their disease. Recent studies suggest that leukaemic stem cells (LSCs) drive AML relapse by residing in the bone marrow niche and adapting their metabolic profile. Metabolic adaptation and LSC plasticity are novel hallmarks of leukemogenesis that provide important biological processes required for tumour initiation, progression and therapeutic responses. These findings highlight the importance of targeting metabolic pathways in leukaemia biology which might serve as the Achilles’ heel for the treatment of AML relapse. In this review, we highlight the metabolic differences between normal haematopoietic cells, bulk AML cells and LSCs. Specifically, we focus on four major metabolic pathways dysregulated in AML; (i) glycolysis; (ii) mitochondrial metabolism; (iii) amino acid metabolism; and (iv) lipid metabolism. We then outline established and emerging drug interventions that exploit metabolic dependencies of leukaemic cells in the treatment of AML. The metabolic signature of AML cells alters during different biological conditions such as chemotherapy and quiescence. Therefore, targeting the metabolic vulnerabilities of these cells might selectively eradicate them and improve the overall survival of patients with AML

Ethics as core curriculum in Science?

Ethics as core curriculum in Science? Jeff F Trahair* & Denise Gamble# Discipline of Anatomy & Pathology*, Philosophy#, University of Adelaide, SA *[email protected] Scientific reasoning, while valuable for its own sake in reliably extending knowledge, is also valued as it often leads to applications which alleviate human problems and enhance human lives. Yet at the same time it requires us to engage in complex decision-making about who and what we want to be. The ethical and moral dimensions of science go well beyond the scope of the laboratory bench. To be engaged as both agents, and empathetic and sympathetic participants in making decisions, scientists need to be educated in ethics. For 12 years we have been successfully teaching an ethics subject: Ethics, Science & Society, enrolling mainly Science and Health Science students. Over the years we have identified key features in successfully teaching ethics in a science curriculum: a cross-faculty/disciplinary design, management and delivery; a focus on topical issues; a balance of didactic and reflective pedagogies; strong community engagement where the situations of ‘real-life’ moral dilemmas are presented, and experiential workshops to foster moral imagination

Free vibration of axially loaded thin-walled composite box beams

A general analytical model applicable to flexural–torsional coupled vibration of thin-walled composite box beams with arbitrary lay-ups under a constant axial force has been presented. This model is based on the classical lamination theory and accounts for all the structural coupling coming from the material anisotropy. Equations of motion are derived from the Hamilton’s principle. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results are obtained for thin-walled composite box beams to investigate the effects of axial force, fiber orientation and modulus ratio on the natural frequencies, load–frequency interaction curves and corresponding vibration mode shapes

On sixfold coupled buckling of thin-walled composite beams

A general analytical model based on shear-deformable beam theory has been developed to study the flexural–torsional coupled buckling of thin-walled composite beams with arbitrary lay-ups under axial load. This model accounts for all the structural coupling coming from the material anisotropy. The seven governing differential equations for coupled flexural–torsional–shearing buckling are derived. The resulting coupling is referred to as sixfold coupled buckling. Numerical results are obtained for thin-walled composite beams to investigate effects of shear deformation, fiber orientation and modulus ratio on the critical buckling loads and corresponding mode shapes

Comparative effects of glucose and water drinks on blood pressure and cardiac function in older subjects with and without postprandial hypotension

Postprandial hypotension (PPH) occurs frequently and is thought to reflect an inadequate increase in cardiac output to compensate for the rise in splanchnic blood flow after a meal. Gastric distension by water attenuates the postprandial fall in blood pressure (BP). Cardiac hemodynamics (stroke volume (SV), cardiac output (CO), and global longitudinal strain (GLS)) have hitherto not been measured in PPH We sought to determine the comparative effects of water and glucose drinks on cardiac hemodynamics in healthy older subjects and individuals with PPH Eight healthy older subjects (age 71.0 ± 1.7 years) and eight subjects with PPH (age 75.5 ± 1.0 years) consumed a 300 mL drink of either water or 75 g glucose (including 150 mg 13C-acetate) in randomized order. BP and heart rate (HR) were measured using an automatic device, SV, CO, and GLS by transthoracic echocardiography and gastric emptying by measurement of 13CO2 In both groups, glucose decreased systolic BP (P < 0.001) and increased HR, SV, and CO (P < 0.05 for all). The fall in systolic BP was greater (P < 0.05), and increase in HR less (P < 0.05), in the PPH group, with no difference in SV or CO Water increased systolic BP (P < 0.05) in subjects with PPH and, in both groups, decreased HR (P < 0.05) without affecting SV, CO, or GLS In subjects with PPH, the hypotensive response to glucose and the pressor response to water were related (R = -0.75, P < 0.05). These observations indicate that, in PPH, the hypotensive response to oral glucose is associated with inadequate compensatory increases in CO and HR, whereas the pressor response to water ingestion is maintained and, possibly, exaggerated.Laurence G. Trahair, Sharmalar Rajendran, Renuka Visvanathan, Matthew Chapman, Daniel Stadler, Michael Horowitz and Karen L. Jone

Optimal prestressing of triple-bay prestressed stayed columns

A nonlinear finite element model of a triple-bay prestressed stayed column is developed within the commercial package ABAQUS. A linearly obtained 'optimal prestressing force' that maximizes the critical buckling load is investigated since this quantity has been demonstrated in previous work on single-bay prestressed columns to provide a lower bound to the actual maximum load carrying capacity when compared to experimental results and nonlinear modelling. The ratio of the crossarm to the overall column length, the diameter of the cable stays, the relative lengths of the individual crossarms and the ratio of the initial prestressing force to the aforementioned linear optimal prestress are varied. Measures for the relative efficiency of the main column and the stays are defined and the objective of the optimization study is for the efficiency to be maximized. It is found that the true optimal prestress is generally higher than the equivalent, linearly obtained, quantity but by a significantly reduced factor when compared to an equivalent study for single-bay prestressed stayed columns

On triply coupled vibrations of axially loaded thin-walled composite beams

Free vibration of axially loaded thin-walled composite beams with arbitrary lay-ups is presented. This model is based on the classical lamination theory, and accounts for all the structural coupling coming from material anisotropy. Equations of motion for flexural–torsional coupled vibration are derived from the Hamilton’s principle. The resulting coupling is referred to as triply coupled vibrations. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results are obtained for thin-walled composite beams to investigate the effects of axial force, fiber orientation and modulus ratio on the natural frequencies, load–frequency interaction curves and corresponding vibration mode shapes