PIV Investigation of the Flow Field Underneath a Generic High-Speed Train Configuration

In this paper a 2C PIV measurement of the flow field underneath a 1:50 generic high-speed train configuration (front car, 2 coaches and tail car) and a smooth generic high-speed train configuration (the same model but without bogies and the bogie cut outs and inter car gaps filled) hauled through a water towing tank at a speed of 4 m/s is presented. The 2C PIV set-up was installed so that the vertical plane (XZ) between the ground and the train, in the centre line of the train, could be measured. The PIV system that was used could measure with an acquisition rate of 10 Hz, at this frequency 6 PIV images of the instantaneous flow field with a distance of 0.4 m from each other were made per run. The total field of view was 0.065 m x 0.025 m (WxH), to cover the entire flow field underneath the train model the position had to be shifted 8 times this was realized with the help of a trigger system. At every position 10 runs were made from which the ensemble average was calculated and reconstructed with the known shift, leading to the average flow field underneath the generic high-speed train configuration. All the presented results in this paper are from the calculated ensemble aver-age. The PIV measurement technique was applicable to measure the flow field underneath a down scaled train model in a water towing tank. The generic high-speed train configuration was compared to a full scale measurement. The same structure of the flow field was found for the flow around the head and the tail of the train. The flow field was fully developed at the begin-ning of the 2nd coach for both configurations. This also agrees with the full scale measure-ment. To achieve more realistic results in the future the simplified bogies that were used should be replaced with bogies with a higher degree of details. For the comparison between the two measured configurations a clear difference was found, the generic high-speed train configuration had a higher induced velocity underneath the train due to the protruding bogie

Wind tunnel experiments with a high speed train model under crosswind conditions

Cross wind stability is one of the most relevant safety topics for the development of modern high-speed trains. New materials and better construction principles reduce the weight of train cars. Combining double deck configurations with an increased cross-sectional area which are developed to increase passenger capacities with higher operational speeds, the effect of cross winds on the driving dynamic behaviour of the train increases dramatically. Wind tunnel experiments were performed in the Side Wind Test Facility Göttingen (SWG) and the Cryogenic Wind Tunnel Cologne (KKK). The measurements in SWG were performed to study the leeward velocity field of the NGT2 double deck high-speed train under cross wind conditions with particle image velocimetry (PIV) and its influence on the induced aerodynamic loads with force measurements at Reynolds numbers of up to 4.00E+05. For detailed investigations of the Reynolds number effects on the aerodynamic loads the configurations used in the SWG were also used in the KKK with the same test setup up to Reynolds numbers of 7.50E+05. The KKK has the option to increase the Reynolds number by a factor of up to 5.5 by reducing the gas temperature using liquid nitrogen and to vary both Reynolds number and Mach number independently

Combination of whole genome sequencing and supervised machine learning provides unambiguous identification of eae-positive Shiga toxin-producing Escherichia coli

Introduction: The objective of this study was to develop, using a genome wide machine learning approach, an unambiguous model to predict the presence of highly pathogenic STEC in E. coli reads assemblies derived from complex samples containing potentially multiple E. coli strains. Our approach has taken into account the high genomic plasticity of E. coli and utilized the stratification of STEC and E. coli pathogroups classification based on the serotype and virulence factors to identify specific combinations of biomarkers for improved characterization of eae-positive STEC (also named EHEC for enterohemorrhagic E.coli) which are associated with bloody diarrhea and hemolytic uremic syndrome (HUS) in human. Methods: The Machine Learning (ML) approach was used in this study on a large curated dataset composed of 1,493 E. coli genome sequences and 1,178 Coding Sequences (CDS). Feature selection has been performed using eight classification algorithms, resulting in a reduction of the number of CDS to six. From this reduced dataset, the eight ML models were trained with hyper-parameter tuning and cross-validation steps. Results and discussion: It is remarkable that only using these six genes, EHEC can be clearly identified from E. coli read assemblies obtained from in silico mixtures and complex samples such as milk metagenomes. These various combinations of discriminative biomarkers can be implemented as novel marker genes for the unambiguous EHEC characterization from different E. coli strains mixtures as well as from raw milk metagenomesPeer Reviewe

Arterial branching and basal ganglia lacunes: a study in pure small vessel disease

Introduction: Lacunes are defined morphologically by size and location, but radiological characteristics alone may be unable to distinguish small vessel disease aetiology from alternative mechanisms. We investigated the branching order of arterial vessels associated with basal ganglia lacunes in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), in order to improve the understanding of their pathogenesis in pure cerebral small vessel disease. Patients and methods: Adults with a confirmed diagnosis of CADASIL were included. A pilot study was conducted in a Scottish CADASIL cohort. The Paris–Munich CADASIL cohort was used for independent validation. Lacunes identified on T1-weighted magnetic resonance imaging scans were registered to a standard brain template. A microangiographic template of the basal ganglia vasculature was automatically overlaid onto coronal slices, and raters estimated the vessel branching order related to each lacune. Results: Of 179 lacunes, 150 (84%) were associated with third-order vessels. In 14 incident lacunes, 11 (79%) were associated with third-order vessels. In the pilot study, lacune volume was significantly lower in lacunes associated with third-order vessels (0.04 ml 0.04 ml) compared to second-order vessels (0.48 0.16 ml; p < 0.001). Discussion: In this study of CADASIL patients, most lacunes were small and associated with third-order vessel disease. This suggests that these are the vessels primarily affected in cerebral small vessel disease. Microangiographic template techniques could be used to further investigate in a general stroke population whether finding large lacunes originating from higher order vessels indicates an alternative cause of stroke. Conclusion: Lacunes in pure small vessel disease are associated with the smallest vessels in the basal ganglia

Impacts of coastal dynamics on the socio-economic component of the Yukon coast, western Canadian Arctic

The Yukon coast has a vivid history reaching back to the pre-historic time of the Thule Inuit. It also archives the diverse story of the Inuvialuit and their traditional and modern lifestyle, and the influences of western cultures. These cultural sites, as well as infrastructure and boating routes, which are nowadays used by the local population, are particularly vulnerable to coastal erosion. To assess this threat, shoreline change dynamics were analyzed along a 210 km long stretch of the Yukon coast by means of geo-coded aerial imagery from the 1950s, 1970s and 1990s, as well as Geo Eye 1 and World View 2 satellite images from 2011. The calculated rates of shoreline change were used to create a conservative (S1) and a dynamic (S2) scenario for possible shoreline positions for the year 2100. The future shoreline positions were then compared to locations of cultural features obtained from a Parks Canada database, the Yukon Archaeological Program and derived from existing literature, as well as from aerial photographs and videos. In total 168 features were mapped, 26 % have been already lost due to coastal erosion and further 20 % (S1) to 26 % (S2) are expected to get lost due to future shoreline retreat, summing up to a total of 46 % (S1) to 52 % (S2) of lost cultural features by 2100. Under both scenarios, the sparse infrastructure in the form of two landing strips will be severely damaged by 2100, considerably restricting its usage. Expected higher sedimentation rates will likely lead to increasing difficulties in navigating the Workboat Passage, which is an important boating route for local travelers. Thus, expected future coastal erosion and sedimentation processes will lead to the disappearance of various cultural sites and impede travelling along the Yukon coast

Impacts of past and future coastal changes on the Yukon coast — threats for cultural sites, infrastructure, and travel routes

Yukon’s Beaufort coast, Canada, is a highly dynamic landscape. Cultural sites, infrastructure, and travel routes used by the local population are particularly vulnerable to coastal erosion. To assess threats to these phenomena, rates of shoreline change for a 210 km length of the coast were analyzed and combined with socioeconomic and cultural information. Rates of shoreline change were derived from aerial and satellite imagery from the 1950s, 1970s, 1990s, and 2011. Using these data, conservative (S1) and dynamic (S2) shoreline projections were constructed to predict shoreline positions for the year 2100. The locations of cultural features in the archives of a Parks Canada database, the Yukon Archaeological Program, and as reported in other literature were combined with projected shoreline position changes. Between 2011 and 2100, approximately 850 ha (S1) and 2660 ha (S2) may erode, resulting in a loss of 45% (S1) to 61% (S2) of all cultural features by 2100. The last large, actively used camp area and two nearshore landing strips will likely be threatened by future coastal processes. Future coastal erosion and sedimentation processes are expected to increasingly threaten cultural sites and influence travelling and living along the Yukon coast

Mutations in the gdpP gene are a clinically relevant mechanism for β-lactam resistance in meticillin-resistant Staphylococcus aureus lacking mec determinants

In Staphylococcus aureus, resistance to β-lactamase stable β-lactam antibiotics is mediated by the penicillinbinding protein 2a, encoded by mecA or by its homologues mecB or mecC. However, a substantial number of meticillin-resistant isolates lack known mec genes and, thus, are called meticillin resistant lacking mec (MRLM). This study aims to identify the genetic mechanisms underlying the MRLM phenotype. A total of 141 MRLM isolates and 142 meticillin-susceptible controls were included in this study. Oxacillin and cefoxitin minimum inhibitory concentrations were determined by broth microdilution and the presence of mec genes was excluded by PCR. Comparative genomics and a genome-wide association study (GWAS) approach were applied to identify genetic polymorphisms associated with the MRLM phenotype. The potential impact of such mutations on the expression of PBP4, as well as on cell morphology and biofilm formation, was investigated. GWAS revealed that mutations in gdpP were significantly associated with the MRLM phenotype. GdpP is a phosphodiesterase enzyme involved in the degradation of the second messenger cyclic-di-AMP in S. aureus. A total of 131 MRLM isolates carried truncations, insertions or deletions as well as amino acid substitutions, mainly located in the functional DHH-domain of GdpP. We experimentally verified the contribution of these gdpP mutations to the MRLM phenotype by heterologous complementation experiments. The mutations in gdpP had no effect on transcription levels of pbp4; however, cell sizes of MRLM strains were reduced. The impact on biofilm formation was highly strain dependent. We report mutations in gdpP as a clinically relevant mechanism for β-lactam resistance in MRLM isolates. This observation is of particular clinical relevance, since MRLM are easily misclassified as MSSA (meticillin-susceptible S. aureus), which may lead to unnoticed spread of β-lactam-resistant isolates and subsequent treatment failure.Peer Reviewe