Blood flow and coherent vortices in the normal and aneurysmatic aortas: a fluid dynamical approach to intra-luminal thrombus formation

Abdominal aortic aneurysms (AAAs) are frequently characterized by the development of an intra-luminal thrombus (ILT), which is known to have multiple biochemical and biomechanical implications. Development of the ILT is not well understood, and shear–stress-triggered activation of platelets could be the first step in its evolution. Vortical structures (VSs) in the flow affect platelet dynamics, which motivated the present study of a possible correlation between VS and ILT formation in AAAs. VSs educed by the λ2-method using computational fluid dynamics simulations of the backward-facing step problem, normal aorta, fusiform AAA and saccular AAA were investigated. Patient-specific luminal geometries were reconstructed from computed tomography scans, and Newtonian and Carreau–Yasuda models were used to capture salient rheological features of blood flow. Particularly in complex flow domains, results depended on the constitutive model. VSs developed all along the normal aorta, showing that a clear correlation between VSs and high wall shear stress (WSS) existed, and that VSs started to break up during late systole. In contrast, in the fusiform AAA, large VSs developed at sites of tortuous geometry and high WSS, occupying the entire lumen, and lasting over the entire cardiac cycle. Downward motion of VSs in the AAA was in the range of a few centimetres per cardiac cycle, and with a VS burst at that location, the release (from VSs) of shear-stress-activated platelets and their deposition to the wall was within the lower part of the diseased artery, i.e. where the thickest ILT layer is typically observed. In the saccular AAA, only one VS was found near the healthy portion of the aorta, while in the aneurysmatic bulge, no VSs occurred. We present a fluid-dynamics-motivated mechanism for platelet activation, convection and deposition in AAAs that has the potential of improving our current understanding of the pathophysiology of fluid-driven ILT growth

Conservation research in times of COVID-19 - the rescue of the northern white rhino

COVID-19 has changed the world at unprecedented pace. The measures imposed by governments across the globe for containing the pandemic have severely affected all facets of economy and society, including scientific progress. Сonservation research has not been exempt from these negative effects, which we here summarize for the BioRescue project, aiming at saving the northern white rhinoceros (Ceratotherium simum cottoni), an important Central African keystone species, of which only two female individuals are left. The development of advanced assisted reproduction and stem-cell technologies to achieve this goal involves experts across five continents. Maintaining international collaborations under conditions of national shut-down and travel restrictions poses major challenges. The associated ethical implications and consequences are particularly troublesome when it comes to research directed at protecting biological diversity – all the more in the light of increasing evidence that biodiversity and intact ecological habitats might limit the spread of novel pathogens

Insights Toward an Ethical Assessment of CubeSat Technologies

The rise of new technology usually comes with new ethical questions. The technology behind cube satellites and small satellites is no exception. This chapter provides an overview of some of the main ethical issues involved in these specific technologies. We consider the relevant issues by distinguishing between anthropological, environmental, and social concerns. Most of these problems appear to be connected to different degrees, and together they show how so-called CubeSats can influence human life on Earth. For this reason, it is important to delineate a narrow and a broad interpretation of space ethics, the latter of which we take to be most appropriate for an assessment of this technology. The effects of these technologies on different stakeholders will also be considered through the outlining of an Ethical Matrix to identify the conflicts that will eventually appear throughout different scenarios of their use

Containers and substrates in the production of seedlings, development and phenology of small fruits

The objective of this work was to test new alternatives for the production of seedlings of small fruits, as well as to evaluate their development and phenology in different containers and substrates. The work was divided into three experiments. In the first experiment, the objective of the work was to evaluate the use of different substrates in the ex vitro rooting of 'Fall Gold' raspberry micro-cuttings. After 60 days, was evaluated: the percentage of surviving seedlings, shoot length, number of roots, length of the largest root, mass of fresh matter and dry matter mass of shoot and root. In the second experiment, the objective of this work was to evaluate the use of different substrates and container volumes in the development of 'Xavante' blackberry seedlings. The evaluations were performed monthly during twelve months of the installation of the experiment and were evaluated: percentage of survival, length of the largest stem, number of stems per plant, number of shoots, length of largest shoot (cm) and mass of root dry matter. In the third experiment, the objective of this work was to evaluate the duration, in days, of the phenological stages for 'Xavante' blackberry in different container volumes and different substrates. The duration (in days) of each phenological stage in each plant was verified as follows: beginning of flowering bud, beginning of flowering, beginning of fruit maturation and beginning of fruit harvest. A stem dormant per stem was also identified for evaluations of fruit phenology and the duration (in days) of the following stages of fruit development: dormant bud, bud sprouting, flower bud, partially open flower, open flower, green berry, partially pink berry, pink berry and ripe berry. In the first experiment, it was concluded that the use of the substrate S10-Beifort® or of the vermiculite+coconut fiber mixture were the favorable results for the rooting of 'Fall Gold' raspberry seedlings. In the second experiment, it was concluded that blackberry 'Xavante' presented adequate development in coconut fiber substrate, with 30-liter containers, at 360 days of cultivation. In the third experiment, the phenological stages showed, on average, the same number of days independent of the substrate and the container observed.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESO objetivo deste trabalho foi testar novas alternativas para a produção de mudas de pequenas frutas, bem como avaliar o desenvolvimento e a fenologia das mesmas, em diferentes recipientes e substratos. O trabalho foi dividido em três experimentos. No primeiro experimento, o objetivo do trabalho foi avaliar o uso de diferentes substratos no enraizamento ex vitro de microestacas de framboeseira ‘Fall Gold’. Após 60 dias foram avaliadas: porcentagem de sobrevivência, comprimento da parte aérea, número de raízes, comprimento da maior raiz, massa de matéria fresca e massa de matéria seca da parte aérea e da raiz. No segundo experimento, o objetivo do trabalho foi avaliar o uso de substratos e volumes de recipientes no desenvolvimento de mudas de amoreira-preta ‘Xavante’. As avaliações foram realizadas mensalmente durante doze meses da instalação do experimento e foram avaliados: porcentagem de sobrevivência, comprimento da maior haste, número de hastes por planta, número de rebentos, comprimento do maior rebento e massa de matéria seca da raiz. No terceiro experimento, o objetivo do trabalho foi avaliar a duração, em dias, dos estádios fenológicos para a amora-preta ‘Xavante’ em diferentes volumes de recipientes e substratos. A duração (em dias) de cada estádio fenológico em cada planta foi verificada da seguinte forma: início da brotação da gema florífera, início da floração, início da maturação do fruto e início da colheita de frutos. Também foram identificadas uma gema dormente por haste, para avaliações de fenologia de frutos e foram avaliadas a duração (em dias) dos seguintes estádios de desenvolvimento de frutos: gema dormente, gema brotando, botão de flor, flor parcialmente aberta, flor aberta, baga verde, baga parcialmente rosada, baga cor-de-rosa e baga madura. No primeiro experimento, conclui-se, que para o enraizamento de microesatacas de framboeseira ‘Fall Gold’, o uso do substrato S10-Beifort® ou da mistura de vermiculita+fibra de coco são os que apresentaram resultados favoráveis. Já no segundo experimento, concluiu-se que plantas de amoreira-preta ‘Xavante’ apresentaram desenvolvimento adequado em substrato fibra de coco, com recipientes de 30 litros, aos 360 dias de cultivo. No terceiro experimento, os estádios fenológicos apresentaram, em média, a mesma duração, independente do substrato e do recipiente

Flow disturbances in stent-related coronary evaginations: a computational fluid-dynamic simulation study

Aims: Angiographic ectasias and aneurysms in stented segments have been associated with late stent thrombosis. Using optical coherence tomography (OCT), some stented segments show coronary evaginations reminiscent of ectasias. The purpose of this study was to explore, using computational fluid-dynamic (CFD) simulations, whether OCT-detected coronary evaginations can induce local changes in blood flow. Methods and results: OCT-detected evaginations are defined as outward bulges in the luminal vessel contour between struts, with the depth of the bulge exceeding the actual strut thickness. Evaginations can be characterised cross ectionally by depth and along the stented segment by total length. Assuming an ellipsoid shape, we modelled 3-D evaginations with different sizes by varying the depth from 0.2-1.0 mm, and the length from 1-9 mm. For the flow simulation we used average flow velocity data from non-diseased coronary arteries. The change in flow with varying evagination sizes was assessed using a particle tracing test where the particle transit time within the segment with evagination was compared with that of a control vessel. The presence of the evagination caused a delayed particle transit time which increased with the evagination size. The change in flow consisted locally of recirculation within the evagination, as well as flow deceleration due to a larger lumen - seen as a deflection of flow towards the evagination. Conclusions: CFD simulation of 3-D evaginations and blood flow suggests that evaginations affect flow locally, with a flow disturbance that increases with increasing evagination size