Microscopic Haematuria

A 30 year old man is referred for a medical check up before taking a life insurance policy. He is asymptomatic, gives no relevant history, is on no treatment and physical examination is unremarkable. Routine dip-stick analysis of a mid­stream specimen of urine reveals traces of blood. What is to be done?peer-reviewe

Measuring β-cell function in vivo to understand the pathophysiology of type 2 diabetes

Diabetes arises when insulin secretion is inadequate for the prevailing metabolic conditions. As such appropriate measurement of β-cell function is necessary for a better understanding of the pathophysiology of prediabetes and diabetes. Unfortunately this is not a straightforward process and requires utilization of mathematical modelling to best appreciate its complexities. This is because insulin concentrations in the plasma represent a balance between the processes of secretion, hepatic extraction and clearance. In isolation such simple measures reveal very little about β-cell function. Moreover, since insulin lowers glucose accounting for the effect of the former on the latter it is a key part of understanding insulin action. The development of the minimal model has allowed simultaneous measurement of the dynamic relationship between insulin secretion and insulin action and produces a quantitative number – the Disposition Index – which quantifies β-cell function. At present this remains the best functional measure of islet health, however, it may not capture other phenotypes such as β-cell senescence or the effect of incretin hormones on β-cell function. Future ongoing development and interaction with other technologies, such as functional imaging, should enhance the contribution of this functional testing to the prevention, treatment and understanding of type 2 diabetes.peer-reviewe

Wrinkling in the deflation of elastic bubbles

The protein hydrophobin HFBII self-assembles into very elastic films at the surface of water; these films wrinkle readily upon compression. We demonstrate and study this wrinkling instability in the context of non-planar interfaces by forming HFBII layers at the surface of bubbles; the interfaces are then compressed by deflating the bubble. By varying the initial concentration of the hydrophobin solutions, we are able to show that buckling occurs at a critical packing fraction of protein molecules on the surface. Independent experiments show that at this packing fraction the interface has a finite positive surface tension, and not zero surface tension as is usually assumed at buckling. We attribute this non-zero wrinkling tension to the finite elasticity of these interfaces. We develop a simple geometrical model for the evolution of the wrinkle length with further deflation, and show that wrinkles start close to the needle used for deflation and grow rapidly towards the mid-plane of the bubble. This geometrical model yields predictions for the length of wrinkles in good agreement with experiments, independently of the rheological properties of the adsorbed layer

Indentation of ultrathin elastic films and the emergence of asymptotic isometry

We study the indentation of a thin elastic film floating at the surface of a liquid. We focus on the onset of radial wrinkles at a threshold indentation depth and the evolution of the wrinkle pattern as indentation progresses far beyond this threshold. Comparison between experiments on thin polymer films and theoretical calculations shows that the system very quickly reaches the Far from Threshold (FT) regime, in which wrinkles lead to the relaxation of azimuthal compression. Furthermore, when the indentation depth is sufficiently large that the wrinkles cover most of the film, we recognize a novel mechanical response in which the work of indentation is transmitted almost solely to the liquid, rather than to the floating film. We attribute this unique response to a nontrivial isometry attained by the deformed film, and discuss the scaling laws and the relevance of similar isometries to other systems in which a confined sheet is subjected to weak tensile loads.Comment: 5 pages, close to published versio

Elastometry of deflated capsules elastic moduli from shape and wrinkle analysis

Elastic capsules, prepared from droplets or bubbles attached to a capillary (as in a pendant drop tensiometer), can be deflated by suction through the capillary. We study this deflation and show that a combined analysis of the shape and wrinkling characteristics enables us to determine the elastic properties in situ. Shape contours are analyzed and fitted using shape equations derived from nonlinear membrane-shell theory to give the elastic modulus, Poisson ratio and stress distribution of the membrane. We include wrinkles, which generically form upon deflation, within the shape analysis. Measuring the wavelength of wrinkles and using the calculated stress distribution gives the bending stiffness of the membrane. We illustrate this method on two very different capsule materials: polymerized octadecyltrichlorosilane (OTS) capsules and hydrophobin (HFBII) coated bubbles. Our results are in agreement with the available rheological data. For hydrophobin coated bubbles the method reveals an interesting nonlinear behavior consistent with the hydrophobin molecules having\ud a rigid core surrounded by a softer shell

Establishing the comparative durability of African mahogany (Khaya senegalensis) in weather exposed above-ground applications

This study was established to evaluate the natural durability of ten- and twenty-year-old plantation-grown Khaya senegalensis (African mahogany) above ground. Whilst mature African mahogany heartwood is expected to last five to 15 years in ground, Australian natural durability standards and specifications do not currently provide information on the durability performance of African mahogany when used above ground. A ground proximity field test was installed at DAFF’s South Johnstone Research Facility in north Queensland and modified ground proximity tests were also installed in a fungal cellar at DAFF’s Salisbury Research Facility near Brisbane. Whilst the plantation African mahogany tested appears more durable than pine, it is not yet possible to determine if its’ durability is consistent with expectations for durability class 3 or durability class 2 timbers above ground. Minimal decay of test specimens had occurred after 12 months and more time is required before reliable conclusions can be drawn. Data gathered, however, are vital for any future durability modelling for plantation African mahogany, to calculate the lag for decay initiation and rates of decay

Elasticity of an interfacial particle raft

We study the collective behaviour of a close packed monolayer of non-Brownian particles at a fluid-liquid interface. Such a particle raft forms a two-dimensional elastic solid and can support anisotropic stresses and strains, e.g. it buckles in uniaxial compression and cracks in tension. We characterise this solid in terms of a Young's modulus and Poisson ratio derived from simple theoretical considerations and show the validity of these estimates by using an experimental buckling assay to deduce the Young's modulus.Comment: 7 pages, 5 figure

Understanding How Lipopolysaccharide Impacts CD4 T Cell Immunity

Lipopolysaccharide (LPS) is a natural adjuvant synthesized by gram-negative bacteria that has profound effects on CD4 T cell responses. LPS stimulates cells through Toll-like receptor 4 (TLR4), causing the release of inflammatory cytokines and upregulation of costimulatory molecules on antigen presenting cells. The combination of signals from antigen, costimulation, and cytokines allow CD4 T cells to overcome suppressive barriers and accumulate in large numbers. T cells that are primed in an LPS-stimulated environment are programmed for long-term survival following clonal expansion. LPS is well-known for generating Th1 responses, however, under appropriate conditions it can also support differentiation into other T helper lineages, demonstrating its pleiotropic nature. Although molecular analyses have provided insights into how immune responses are controlled by LPS in vivo, its powerful adjuvant activity is also associated with toxicity. Research on partial TLR4 agonists such as monophosphoryl lipid A have demonstrated that toxicity and immunogenicity are not always linked, making them useful candidates for human vaccines. In this sense, many years of LPS research have ultimately contributed to vaccine design, and the next generation may involve studying how the balance between different CD4 T cell subsets is controlled

Understanding the economic contribution of tourism in Malta : a literature review

The paper presents a critical assessment of the key studies which present empirical estimates for the contribution of the tourism sector to the Maltese economy. The observed discrepancies in the estimates derived from these studies has in part led to a situation in which there is an effective widespread divergence relating to the specific economic contribution of tourism in Malta. The paper evaluates the estimates derived by these key studies in the context of both the strengths and weaknesses of their respective modelling frameworks, which range from the construction of tourism satellite accounts, to input-output models and computable general equilibrium modelling, as well as an evaluation of the overall quality of the data utilized. The paper therefore attempts to identify and clarify the main causes behind the observed variations in the resulting estimates and through a systematic comparative assessment also aid in the providing a further understanding of the potential economic contribution of tourism to the Maltese economy. On the basis of this assessment it is suggested that the contribution of tourism to the Maltese economy should account for approximately 5.7% of total gross value added when taking account solely direct effects, 12% once indirect effects are included and roughly 17% accounting also for the induced effects. Furthermore, on the basis of this assessment the paper highlights the need for further research in this area given the significance of the tourism sector to the small island economy of Malta.peer-reviewe

Solution of the Percus-Yevick equation for hard discs

We solve the Percus-Yevick equation in two dimensions by reducing it to a set of simple integral equations. We numerically obtain both the pair correlation function and the equation of state for a hard disc fluid and find good agreement with available Monte-Carlo calculations. The present method of resolution may be generalized to any even dimension.Comment: 9 pages, 3 figure