1. Wochenbericht AL519-1

Wochenbericht AL519-1 (23.-27.01.2019) [Alkor

2. Wochenbericht AL519-1

Wochenbericht AL519-1 (28.01.-03.02.2019) [Alkor

Comportamento do osso cortical submetido a processos de furação

O principal objetivo deste estudo é avaliar o desenvolvimento da necrose térmica e/ou desgaste ósseo durante um processo de furação em materiais compósitos com estrutura similar ao tecido ósseo cortical. As fases de trabalho contemplam a leitura do campo de temperaturas nos modelos biomecânicos através de um processo de furação, o campo de deformações através da utilização da extensometria, leitura da temperatura gerada na broca após o processo de furação através de imagens termográficas e análise térmica e mecânica a partir de um modelo de elementos finitos. Foram tomadas considerações sobre a escolha dos biomateriais, dimensões do modelo e do processo de furação tendo em conta diversas variáveis, como a velocidade, diâmetro e comprimento da broca. Com este trabalho, utilizando um procedimento experimental e numérico, pretende-se verificar a interação entre a alteração da velocidade de avanço com a mesma velocidade de rotação e diâmetro de broca, no aumento da temperatura e de deformações no tecido cortical em estudo. Os métodos experimentais utilizados em laboratório são baseados nas técnicas de termografia, extensometria e aplicação de termopares durante a furação dos materiais compósitos. Numericamente, são utilizados modelos teóricos, mecânico e térmico, com o recurso à técnica de elementos finitos, para a discussão de resultados. Após a elaboração do presente trabalho conclui-se que a temperatura na broca é superior para uma menor velocidade de avanço. O aumento da velocidade de avanço provoca um decréscimo da temperatura, ou seja, as temperaturas no material são mais elevadas para uma velocidade de avanço inferior. Verificou-se ainda que as temperaturas nos termopares a uma mesma distância da furação são inferiores às temperaturas registadas em distâncias diferentes. Com a diminuição da temperatura as tensões também diminuem, isto é, para uma velocidade de avanço superior as tensões à superfície do material e próximas da furação são inferiores.The primary main objective of this study is to assess the development of thermal necrosis and / or bone wear during a drilling process in composite materials with similar structure to the cortical bone. The working steps include the reading of the temperature field in the biomechanical models through a drilling process, the strain field by using strain gages, temperature reading generated in the drill after drilling the process through and thermographic images collected by thermal analysis and a mechanical analysis using from a finite element model. Considerations have been taken on the choice of biomaterials, model dimensions, and drilling process taking into account several variables such as speed, diameter and length of the drill. This work intends to verify, experimental and numerically, the interaction between the same feed rate and different rotational speeds, with the same cut drill, in the tissue temperature and strain field formation. To this end, composite materials are used with similar characteristics to the cortical bone, with equal densities. The experimental methods used in the laboratory are based on thermography techniques, thermocouples and strain gages used during the drilling of different composite materials. Numerically, theoretical models are used with the finite element technique for the discussion of results. After the preparation of this work is concluded that the temperature in the drill is higher to a lower feed rate. The increase in feed rate causes a decrease in the temperature, i.e., temperatures of the material are higher to a lower feed rate. The temperatures in the thermocouples at the same distance from the hole are lower than the temperatures recorded at different distances. It was found that with decreasing temperature, the stress also decreases, i. e., to a higher feed rate, the surface and the hole surrounding have lower stresses

Persistent effects of sand extraction on habitats and associated benthic communities in the German Bight

Sea-level rise demands for protection measures of endangered coastlines crucial for the local population. At the island of Sylt in the SE North Sea, shoreline erosion is compensated by replenishment with sand dredged from an offshore extraction site. We studied the long-term effects of sand extraction on bathymetry, geomorphology, habitats and benthic fauna. Sand extraction created dredging holes about 1 km in diameter and up to 20 m below the ambient seafloor level. Directly after dredging the superficial sediment layer, inside the pits was dominated by coarse sand and stones. Hydroacoustic surveys revealed only minor changes of bathymetry > 35 years after sand extraction. Obviously, backfill of the dredging pits was very slow, at a rate of a few millimeters per year, presumably resulting from low ambient sediment availability and relatively calm hydrodynamic conditions despite high wave energy during storms. Thus, a complete backfill of the deep extraction sites is likely to take centuries in this area. Hydroacoustic surveys and ground truthing showed that the backfilled material is mainly very fine sand and mud, turning the previously coarse sand surface into a muddy habitat. Accordingly, grab samples revealed significant differences in macrozoobenthos community composition, abundance and species density between recently dredged areas ( 10 years ago) and undisturbed sites (control sites). Overall, dredging turned the original association of sand-dwelling species into a muddy sediment association. Since re-establishment of disturbed benthic communities depends on previous re-establishment of habitat characteristics, the low sedimentation rates indicate that a return to a pre-dredging habitat type with its former benthic community and habitat characteristics is unlikely. Since coarse sand is virtually immobile in this area, a regeneration towards pre-dredging conditions is also unlikely without human interference (e.g., mitigation measures like depositing coarse material on the seafloor to restore the sessile epifauna)

The sustainability of beach nourishments: a review of nourishment and environmental monitoring practice

Beach nourishments are a widely used method to mitigate erosion along sandy shorelines. In contrast to hard coastal protection structures, nourishments are considered as soft engineering, although little is known about the cumulative, long-term environmental effects of both marine sediment extraction and nourishment activities. Recent endeavours to sustain the marine ecosystem and research results on the environmental impact of sediment extraction and nourishment activities are driving the need for a comprehensive up-to-date review of beach nourishment practice, and to evaluate the physical and ecological sustainability of these activities. While existing reviews of nourishment practice have focused on the general design (motivation, techniques and methods, international overview of sites and volumes) as well as legal and financial aspects, this study reviews and compares not only nourishment practice but also the accompanying assessment and monitoring of environmental impacts in a number of developed countries around the world. For the study, we reviewed 205 openly-accessible coastal management strategies, legal texts, guidelines, EIA documents, websites, project reports, press releases and research publications about beach nourishments in several developed countries around the world (Germany, Denmark, the Netherlands, Belgium, Spain, UK, USA and Australia). Where information was not openly available, the responsible authorities were contacted directly. The study elaborates on the differences in coastal management strategies and legislation as well as the large dissimilarities in the EIA procedure (where applicable) for both marine sediment extraction and nourishment activities. The spatial disturbance of the marine environment that is considered a significant impact, a factor which determines the need for an Environmental Impact Assessment, varies substantially between the countries covered in this study. Combined with the large uncertainties of the long-term ecological and geomorphological impacts, these results underline the need to reconsider the sustainability of nourishments as “soft” coastal protection measures

Tools for the Improvement of the Efficiency and Sustainability of Shore Nourishments – Results of the research project STENCIL

Online First, geplanter Druck 202

The sustainability of beach nourishments: a review of nourishment and environmental monitoring practice

Beach nourishments are a widely used method to mitigate erosion along sandy shorelines. In contrast to hard coastal protection structures, nourishments are considered as soft engineering, although little is known about the cumulative, long-term environmental effects of both marine sediment extraction and nourishment activities. Recent endeavours to sustain the marine ecosystem and research results on the environmental impact of sediment extraction and nourishment activities are driving the need for a comprehensive up-to-date review of beach nourishment practice, and to evaluate the physical and ecological sustainability of these activities. While existing reviews of nourishment practice have focused on the general design (motivation, techniques and methods, international overview of sites and volumes) as well as legal and financial aspects, this study reviews and compares not only nourishment practice but also the accompanying assessment and monitoring of environmental impacts in a number of developed countries around the world. For the study, we reviewed 205 openly-accessible coastal management strategies, legal texts, guidelines, EIA documents, websites, project reports, press releases and research publications about beach nourishments in several developed countries around the world (Germany, Denmark, the Netherlands, Belgium, Spain, UK, USA and Australia). Where information was not openly available, the responsible authorities were contacted directly. The study elaborates on the differences in coastal management strategies and legislation as well as the large dissimilarities in the EIA procedure (where applicable) for both marine sediment extraction and nourishment activities. The spatial disturbance of the marine environment that is considered a significant impact, a factor which determines the need for an Environmental Impact Assessment, varies substantially between the countries covered in this study. Combined with the large uncertainties of the long-term ecological and geomorphological impacts, these results underline the need to reconsider the sustainability of nourishments as “soft” coastal protection measures.Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/50110000234

Priming of natural killer cells by nonmucosal mononuclear phagocytes requires instructive signals from commensal microbiota.

Mononuclear phagocytes are an important component of an innate immune system perceived as a system ready to react upon encounter of pathogens. Here, we show that in response to microbial stimulation, mononuclear phagocytes residing in nonmucosal lymphoid organs of germ-free mice failed to induce expression of a set of inflammatory response genes, including those encoding the various type I interferons (IFN-I). Consequently, NK cell priming and antiviral immunity were severely compromised. Whereas pattern recognition receptor signaling and nuclear translocation of the transcription factors NF-κB and IRF3 were normal in mononuclear phagocytes of germ-free mice, binding to their respective cytokine promoters was impaired, which correlated with the absence of activating histone marks. Our data reveal a previously unrecognized role for postnatally colonizing microbiota in the introduction of chromatin level changes in the mononuclear phagocyte system, thereby poising expression of central inflammatory genes to initiate a powerful systemic immune response during viral infection