12 research outputs found
Shedding Light on Vampires: The Phylogeny of Vampyrellid Amoebae Revisited
With the advent of molecular phylogenetic techniques the polyphyly of naked filose amoebae has been proven. They are interspersed in several supergroups of eukaryotes and most of them already found their place within the tree of life. Although the ‘vampire amoebae’ have attracted interest since the middle of the 19th century, the phylogenetic position and even the monophyly of this traditional group are still uncertain. In this study clonal co-cultures of eight algivorous vampyrellid amoebae and the respective food algae were established. Culture material was characterized morphologically and a molecular phylogeny was inferred using SSU rDNA sequence comparisons. We found that the limnetic, algivorous vampyrellid amoebae investigated in this study belong to a major clade within the Endomyxa Cavalier-Smith, 2002 (Cercozoa), grouping together with a few soil-dwelling taxa. They split into two robust clades, one containing species of the genus Vampyrella Cienkowski, 1865, the other containing the genus Leptophrys Hertwig & Lesser, 1874, together with terrestrial members. Supported by morphological data these clades are designated as the two families Vampyrellidae Zopf, 1885, and Leptophryidae fam. nov. Furthermore the order Vampyrellida West, 1901 was revised and now corresponds to the major vampyrellid clade within the Endomyxa, comprising the Vampyrellidae and Leptophryidae as well as several environmental sequences. In the light of the presented phylogenetic analyses morphological and ecological aspects, the feeding strategy and nutritional specialization within the vampyrellid amoebae are discussed
Comparative study between the SORS and Dynamic Strategy visual field testing methods on glaucomatous and healthy subjects
Purpose: To clinically validate the non-inferiority of the Sequentially Optimized Reconstruction Strategy (SORS) when compared to the Dynamic Strategy (DS).
Methods: SORS is a novel perimetry testing strategy that evaluates a subset of test locations of a visual field (VF) test pattern and estimates the untested locations by linear approximation. When testing fewer locations, SORS has shown in computer simulations, to bring improvements in speed over conventional perimetry tests, while maintaining acquisition at high quality acquisition. To validate SORS, a prospective clinical study was conducted at the Department of Ophthalmology of Bern University Hospital, over 12 months. 83 subjects (32 healthy and 51 glaucoma patients with early to moderate visual field loss) out of 114 participants were included in the study. The subjects underwent perimetry tests on an Octopus 900 (Haag-Streit, Koeniz, Switzerland) using the G pattern with both DS and SORS. The acquired sensitivity thresholds (ST) by both tests were analyzed and compared.
Results: DS-acquired VFs were used as a reference. High correlations between individual STs (r > 0.74) as well as between mean defect values (r>0.88) given by DS and SORS were obtained. The mean absolute error of SORS was under 3 dB with a 7o% reduction in acquisition time. SORS overestimated healthy VFs while slightly underestimating glaucomatous VFs. Qualitatively, SORS acquisition yielded VF with detectable defect patterns, albeit some isolated and small defects were occasionally missed.
Conclusion: This clinical study showed that for healthy and glaucomatous patients, SORS-acquired VFs sufficiently correlated with the DS-acquired VFs with up to 70% reduction in acquisition time.
Translational Relevance: This clinical study suggests that the novel perimetry strategy SORS could be used in routine clinical practice with comparable utility to the current standard DS, whereby providing a shorter and more comfortable perimetry experience
Determination of a Numerical Surge Limit by Means of an Enhanced Greitzer Compressor Model
The surge limit of centrifugal compressors is a key parameter in the design process of modern turbochargers. Numerical methods like steady-state simulations are state-of-the-art methods for predicting the performance of the centrifugal compressor. In contrast to that, the determination of the surge limit with any numerical method is still an unsolved challenge. Since the extensive work of Greitzer and many other researchers in this field, it is well-known that surge is a system-dependent phenomenon. In the case of steady-state simulations, the simulation domain is chosen to be as small as possible due to the numerical cost. This simply implies that there is no system information included in the numerical model. Therefore, it is not possible to determine any system-dependent surge limit with today’s applied numerical methods. To overcome this issue, an enhanced Greitzer surge model, which has been developed at Tu Darmstadt, should act as a link between the simulation and the system in which the compressor will be operated. The focus of this paper will rather be on the methodology of determining the surge limit by means of numerical data than on the surge model itself. The methodology will be validated by experimental data of different systems
An interdisciplinary investigation of a recent submarine mass transport deposit at the continental margin off Uruguay
Assessing frequency and extent of mass movement at continental margins is crucial to evaluate risks for offshore constructions and coastal areas. A multidisciplinary approach including geophysical, sedimentological, geotechnical, and geochemical methods was applied to investigate multistage mass transport deposits (MTDs) off Uruguay, on top of which no surficial hemipelagic drape was detected based on echosounder data. Nonsteady state pore water conditions are evidenced by a distinct gradient change in the sulfate (SO42−) profile at 2.8 m depth. A sharp sedimentological contact at 2.43 m coincides with an abrupt downward increase in shear strength from ∼10 to >20 kPa. This boundary is interpreted as a paleosurface (and top of an older MTD) that has recently been covered by a sediment package during a younger landslide event. This youngest MTD supposedly originated from an upslope position and carried its initial pore water signature downward. The kink in the SO42− profile ∼35 cm below the sedimentological and geotechnical contact indicates that bioirrigation affected the paleosurface before deposition of the youngest MTD. Based on modeling of the diffusive re-equilibration of SO42− the age of the most recent MTD is estimated to be <30 years. The mass movement was possibly related to an earthquake in 1988 (∼70 km southwest of the core location). Probabilistic slope stability back analysis of general landslide structures in the study area reveals that slope failure initiation requires additional ground accelerations. Therefore, we consider the earthquake as a reasonable trigger if additional weakening processes (e.g., erosion by previous retrogressive failure events or excess pore pressures) preconditioned the slope for failure. Our study reveals the necessity of multidisciplinary approaches to accurately recognize and date recent slope failures in complex settings such as the investigated area