A higher tier flow-through toxicity test with the green alga Selenastrum capricornutum

A flow-through test system for the assessment of the toxicity of substances to the green alga Selenastrum capricornutum was developed. The dosing of a test substance commenced, once the growth of the algae was in a steady state, i.e. when the dilution rate was equal to the growth rate. The growth rate and hence the effect of the test substance was determined indirectly by the estimation of cell number under consideration of inflow volume over time. The ease of manipulation of the exposure regime via digitally controlled pumps makes this flow-through system also suitable for testing substances under realistic exposure conditions or in combination with their metabolites. In this study the degradation of a herbicide and its metabolites was simulated. The substance with an ErC50 (72 h) of 1.3 microg/l under static conditions (OECD, 1984) was tested in the developed flow-through system. The simulated degradation at an initial dose of 3 microg/l of the herbicide had no effect on algal growth, whereas under static test conditions, an NOErC of 0.28 microg/l was determined. The lowest concentration at which effects were observed was a continuous dose of 6 microg/l.     

A group counseling emphasis at a university counseling center.

Describes a service delivery system with a group personal counseling emphasis, based on the authors' 2 yrs of experience at a university counseling center. The local background and rationale for this system are discussed, and the practical logistics, the operational policies, and the group ground rules are presented. Utilization data are summarized: 36% of all clients and 88% of clients with 8 or more sessions were group members; groups typically grew to 9 clients and had 60% attendance. Results for a self-report outcome survey of 128 students are exemplified by the 95.1% who reported some level of improvement and the 92.2% who rated their psychologist "very" to "exceptionally effective." (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fitting Triangular B-Splines to Functional Scattered Data

Scattered data is, by definition, irregularly spaced. Uniform surface schemes are not well adapted to the locally varying nature of such data. Conversely, Triangular B-Spline surfaces 2 are more flexible in that they can be built over arbitrary triangulations and thus can be adapted to the scattered data. This paper discusses the use of DMS spline surfaces for approximation of scattered data. A method is provided for automatically triangulating the domain containing the points and generating basis functions over this triangulation. A surface approximating the data is then found by a combination of least squares and bending energy minimization. This combination serves both to generate a smooth surface and to accommodate for gaps in the data. Examples are presented which demonstrate the eftectiveness of the technique for mathematical, geographical and other data sets.     

Multi-step density-based clustering

Data mining in large databases of complex objects from scientific, engineering or multimedia applications is getting more and more important. In many areas, complex distance measures are first choice but also simpler distance functions are available which can be computed much more efficiently. In this paper, we will demonstrate how the paradigm of multi-step query processing which relies on exact as well as on lower-bounding approximated distance functions can be integrated into the two density-based clustering algorithms DBSCAN and OPTICS resulting in a considerable efficiency boost. Our approach tries to confine itself to ɛ-range queries on the simple distance functions and carries out complex distance computations only at that stage of the clustering algorithm where they are compulsory to compute the correct clustering result. Furthermore, we will show how our approach can be used for approximated clustering allowing the user to find an individual trade-off between quality and efficiency. In order to assess the quality of the resulting clusterings, we introduce suitable quality measures which can be used generally for evaluating the quality of approximated partitioning and hierarchical clusterings. In a broad experimental evaluation based on real-world test data sets, we demonstrate that our approach accelerates the generation of exact density-based clusterings by more than one order of magnitude. Furthermore, we show that our approximated clustering approach results in high quality clusterings where the desired quality is scalable with respect to (w.r.t.) the overall number of exact distance computations. Stefan Brecheisen is a teaching and research assistant in Prof.$ Hans-Peter Kriegel's group. He works in the field of similarity search in spatial objects. Hans-Peter Kriegel is a full professor at the University of Munich and head of the database group since 1991. He studied computer science at the University of Karlsruhe, Germany, and finished his doctoral thesis there in 1976. He has more than 200 publications in international journals and reviewed conference proceedings. His research interests are database systems for complex objects (molecular biology, medical science, multimedia, CAD, etc.), in particular query processing, similarity search, high-dimensional index structures, as well as knowledge discovery in databases and data mining. Martin Pfeifle is a teaching and research assistant in Prof.$ Hans-Peter Kriegel's group. He finished his doctoral thesis on “Spatial Database Support for Virtual Engineering” in the spring of 2004.     

The signal molecule for beta-lactamase induction in Enterobacter cloacae is the anhydromuramyl-pentapeptide

Beta-lactamase induction in Enterobacter cloacae, which is linked to peptidoglycan recycling, was investigated by high-performance liquid chromatographic analysis of cell wall fragments in genetically defined cells of Escherichia coli. After treatment of cells with beta-lactams, we detected an increase in a D-tripeptide (disaccharide-tripeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid), aD-tetrapeptide (disaccharide-tetrapeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid-D-alanine), and aD-pentapeptide (disaccharide-pentapeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid-D-alanyl-D-alanine)levels in the periplasms of bacterial cells. Furthermore, only the accumulation of aD-pentapeptide correlates with the beta-lactamase-inducing capacity of the beta-lactam antibiotic. The transmembrane protein AmpG transports all three aD-peptides into the cytoplasm, where they are degraded into the corresponding monosaccharide peptides. In the absence of AmpD the constitutive overproduction of beta-lactamase is accompanied by an accumulation of aM-tripeptide (monosaccharide-tripeptide, anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid) and aM-pentapeptide (L1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid-D-alanyl-D-alanine), but not aM-tetrapeptide (anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid-D-alanine), in the cytoplasm. Only the amount of aM-pentapeptide is increased upon treatment with imipenem. These findings indicate that aD-pentapeptide is the main periplasmic muropeptide, which is converted into the cytoplasmic signal molecule for beta-lactamase induction, the aM-pentapeptide.     

Spherical Triangular B-splines with Application to Data Fitting

Triangular B-splines surfaces are a tool for representing arbitrary piecewise polynomial surfaces over planar triangulations, while automatically maintaining continuity properties across patch boundaries. Recently, Alfeld et al. [1] introduced the concept of spherical barycentric coordinates which allowed them to formulate Bernstein-Bézier polynomials over the sphere. In this paper we use the concept of spherical barycentric coordinates to develop a similar formulation for triangular B-splines, which we call spherical triangular B-splines. These splines defined over spherical triangulations share the same continuity properties and similar evaluation algorithms with their planar counterparts, but possess none of the annoying degeneracies found when trying to represent closed surfaces using planar parametric surfaces. We also present an example showing the use of these splines for approximating spherical scattered data.     

Extending metric index structures for efficient range query processing

Databases are getting more and more important for storing complex objects from scientific, engineering, or multimedia applications. Examples for such data are chemical compounds, CAD drawings, or XML data. The efficient search for similar objects in such databases is a key feature. However, the general problem of many similarity measures for complex objects is their computational complexity, which makes them unusable for large databases. In this paper, we combine and extend the two techniques of metric index structures and multi-step query processing to improve the performance of range query processing. The efficiency of our methods is demonstrated in extensive experiments on real-world data including graphs, trees, and vector sets.