Transitional flow in aneurysms and the computation of haemodynamic parameters

Haemodynamic forces appear to play an influential role in the evolution of aneurysms. This has led to numerous studies, usually based on computational fluid dynamics. Their focus is predominantly on the wall shear stress (WSS) and associated derived parameters, attempting to find correlations between particular patterns of haemodynamic indices and regions subjected to disease formation and progression. The indices are generally determined by integration of flow properties over a single cardiac cycle. In this study, we illustrate that in some cases the transitional flow in aneurysms can lead to significantly different WSS distributions in consecutive cardiac cycles. Accurate determination of time-averaged haemodynamic indices may thus require simulation of a large number of cycles, which contrasts with the common approach to determine parameters using data from a single cycle. To demonstrate the role of transitional flow, two exemplary cases are considered: flow in an abdominal aortic aneurysm and in an intracranial aneurysm. The key differences that are observed between these cases are explained in terms of the integral timescale of the transitional flows in comparison with the cardiac cycle duration: for relatively small geometries, transients will decay before the next cardiac cycle. In larger geometries, transients are still present when the systolic phase produces new instabilities. These residual fluctuations serve as random initial conditions and thus seed different flow patterns in each cycle. To judge whether statistics are converged, the derived indices from at least two successive cardiac cycles should be compared.     

Early Age Microstructural Transformations of an Inorganic Polymer Made of Fayalite Slag

Three types of binders were investigated by combining a water granulated fayalite slag and three different activating solutions (NaOH, SH; Na‐silicate, SS; and a 1:1 mixture of the two, SH + SS). A reactivity test proved that the slag dissolves in the alkaline environment, releasing both Si and Al. Through rheological measurements it was found that the most alkaline solution (SH) led to a very fast structure build‐up, followed by the activating solution SS+SH; when SS was used, the storage modulus did not increase even after 2 h. A similar trend was observed by calorimetry, where the paste with SH resulted in heat release within minutes, followed by SH + SS. These transformations were also followed by in situ ATR‐FTIR, indicating changes in the vibrational bands attributed to asymmetric stretching vibration of [SiO₄] with 3 or 4 NBO/Si. In the case of the sample activated with SH, a new band appeared after 96 h and continued to increase in intensity at later times. For SS + SH activating solution, a new band appeared after 96 h, increasing over time, whereas the originally present band at 940 cm^?1 became more distinct. For the sample with only SS, no vibrational changes were detected after 24 h. In conclusion, the fayalite slag is a reactive material that can undergo microstructural changes toward new reaction products, with the choice of the activating solution being a crucial factor in the process.     

Effect of High Cooling Rates on the Mineralogy and Hydraulic Properties of Stainless Steel Slags

This article investigates the effect of chemical composition and cooling rate during solidification on the mineralogy and hydraulic properties of synthetic stainless steel slags. Three synthetic slags, covering the range of typical chemical composition in industrial practice, were subjected to high cooling rates, by melt spinning granulation or quenching in water, and to low cooling rates, by cooling inside the furnace. Both methods of rapid cooling led to volumetrically stable slags unlike the slow cooling which resulted in a powder-like material. Stabilized slags consisted predominantly of lamellar β-dicalcium silicate (β-C₂S) and Mg, Ca-silicates (merwinite and bredigite); the latter form the matrix at low basicity and are segregated along the C₂S grain boundaries at high basicities. Slowly cooled slags consist of the γ-C₂S polymorph instead of the β-C₂S and of less Mg, Ca-silicates. Isothermal conduction calorimetry and thermogravimetric analysis indicate the occurrence of hydration reactions in the stabilized slags after mixing with water, while calcium silicate hydrates (C-S-H) of typical acicular morphology are identified by SEM. The present results demonstrate that the application of high cooling rates can result in a stable, environmental-friendly, hydraulic binder from stainless steel slags, rich in β-C₂S, without the necessity of introducing any additions to arrest the β polymorph.     

Shock Waves Impacting Composite Material Plates: The Mutual Interaction

High-performance, fiber-reinforced polymer composites have been extensively used in structural applications in the last 30 years because of their light weight combined with high specific stiffness and strength at a rather low cost. The automotive industry has adopted these materials in new designs of lightweight vehicles. The mechanical response and characterization of such materials under transient dynamic loading caused with shock impact induced by blast is not well understood. Air blast is associated with a fast traveling shock front with high pressure across followed by a decrease in pressure behind due to expansion waves. The time scales associated with the shock front are typically 10³ faster than those involved in the expansion waves. Impingement of blast waves on structures can cause a reflection of the wave off the surface of the structure followed by a substantial transient aerodynamic load, which can cause significant deformation and damage of the structure. These can alter the overpressure, which is built behind the reflected shock. In addition, a complex aeroelastic interaction between the blast wave and the structure develops that can induce reverberation within an enclosure, which can cause substantial overpressure through multiple reflections of the wave. Numerical simulations of such interactions are quite challenging. They usually require coupled solvers for the flow and the structure. The present contribution provides a physics-based analysis of the phenomena involved, a critical review of existing computational techniques together with some recent results involving face-on impact of shock waves on thin composite plates.     

Molecular Detection of Two Potential Probiotic Lactobacilli Strains and Evaluation of Their Performance as Starter Adjuncts in Yogurt Production

A molecular method for efficient and accurate detection and identification of two potential probiotic lactobacilli strains isolated from fermented olives, namely Lactobacillus pentosus B281 and Lb. plantarum B282, was developed in the present study. Random Amplified Polymorphic DNA (RAPD) analysis was performed, and strain specific primers were designed and applied in a multiplex polymerase chain reaction (PCR) assay. The specificity of the assay was tested and successfully confirmed in 27 and 22 lactobacilli strains for Lb. pentosus B281 and Lb. plantarum B282, respectively. Moreover, the two strains were used as starter cultures in yogurt production. Cell enumeration followed by multiplex PCR analysis demonstrated that the two strains were present in yogurt samples at levels ≥6 log CFU/g even after 35 days of storage at 4 °C. Microbiological analysis showed that lactobacilli and streptococci were present within usual levels, whereas enterobacteriaceae and yeast/mold counts were not detected as expected. Although the pH values of the novel products were slightly lower than the control ones, the yogurt containing the probiotic cultures scored similar values compared to the control in a series of sensory tests. Overall, these results demonstrated the possible use of the two strains as starter adjuncts in the production of yogurt with potential probiotic properties.     

Contribution of the solar energy in the sustainable tourism development of the Mediterranean islands

The purpose of this work is to examine specific features of thermal and photovoltaic solar systems and their contribution to the sustainable tourism development of Mediterranean islands. In doing so, the best practices are studied and the factors which influence the transfer of these practices in other geographic regions are examined. We take under consideration the sensitiveness of many islander Mediterranean regions in relation to the climate changes and the perspective of their economic development through thematic tourism forms and differentiated tourism products and services. At a further step, we present currently developed innovative applications which are specially adapted to the needs identified within this research and we propose marketing strategies for their further expansion. The marketing approach followed is based on an innovative concept, which suggests that solar energy systems could constitute a driver for the development of specific forms of tourism. These systems are mainly the ICS solar water heaters, the coloured flat plate-collectors, the CPC collectors and the hybrid PV/T collectors. Apart from these, the use of booster reflectors that achieve a higher energy output in all cases of the above mentioned collectors is also suggested. We conclude that turning solar energy systems into a driver for specific types of tourism development and consequently of a local economic development is possible, if we take into consideration specific social needs and aspirations.     

A structured autopsy-based audit of 370 firearm fatalities: Contribution to inform policy decisions and the probability of the injured arriving alive at a hospital and receiving definitive care

The objectives of this autopsy-based audit of firearm-related fatalities were to acquire data to inform policy decisions and to assess the probability of the injured arriving alive at a hospital and receiving definitive care.