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

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

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

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

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

Capillary deformations of bendable films

We address the partial wetting of liquid drops on ultrathin solid sheets resting on a deformable foundation. Considering the membrane limit of sheets that can relax compression through wrinkling at negligible energetic cost, we revisit the classical theory for the contact of liquid drops on solids. Our calculations and experiments show that the liquid-solid-vapor contact angle is modified from the Young angle, even though the elastic bulk modulus (E) of the sheet is so large that the ratio between the surface tension γ and E is of molecular size. This finding establishes a new type of “soft capillarity” that stems from the bendability of thin elastic bodies rather than from material softness. We also show that the size of the wrinkle pattern that emerges in the sheet is fully predictable, thus resolving a puzzle noticed in several previous attempts to model “drop-on-a-floating-sheet” experiments, and enabling a reliable usage of this setup for the metrology of ultrathin films

Dynamics of snapping beams and jumping poppers

We consider the dynamic snapping instability of elastic beams and shells. Using the Kirchhoff rod and Föppl-von Kármán plate equations, we study the stability, deformation modes, and snap-through dynamics of an elastic arch with clamped boundaries and subject to a concentrated load. For parameters typical of everyday and technological applications of snapping, we show that the stretchability of the arch plays a critical role in determining not only the post-buckling mode of deformation but also the timescale of snapping and the frequency of the arch's vibrations about its final equilibrium state. We show that the growth rate of the snap-through instability and its subsequent ringing frequency can both be interpreted physically as the result of a sound wave in the material propagating over a distance comparable to the length of the arch. Finally, we extend our analysis of the ringing frequency of indented arches to understand the "pop" heard when everted shell structures snap-through to their stable state. Remarkably, we find that not only are the scaling laws for the ringing frequencies in these two scenarios identical but also the respective prefactors are numerically close; this allows us to develop a master curve for the frequency of ringing in snapping beams and shells

Do ultrafast exciton-polaron decoherence dynamics govern photocarrier generation efficiencies in polymer solar cells?

All-organic-based photovoltaic solar cells have attracted considerable attention because of their low-cost processing and short energy payback time. In such systems the primary dissociation of an optical excitation into a pair of photocarriers has been recently shown to be extremely rapid and efficient, but the physical reason for this remains unclear. Here, two-dimensional photocurrent excitation spectroscopy, a novel non-linear optical spectroscopy, is used to probe the ultrafast coherent decay of photoexcitations into charge-producing states in a polymer:fullerene based solar cell. The two-dimensional photocurrent spectra are interpreted by introducing a theoretical model for the description of the coupling of the electronic states of the system to an external environment and to the applied laser fields. The experimental data show no cross-peaks in the two-dimensional photocurrent spectra, as predicted by the model for coherence times between the exciton and the photocurrent producing states of 20\,fs or less