Quantitative measurement of gas hold-up distribution in a stirred chemical reactor using X-ray cone-beam computed tomography

Cone-beam type X-ray computed tomography (CBCT) is a potential method to measure three-dimensional phase distributions in vessels. An example for that is the measurement of gas profiles in stirred chemical reactors. Such data are highly valuable for the assessment and evaluation of chemical processes, for optimisation of the reactor and stirrer design, and for evaluation of computational fluid dynamics codes used to model the fluid flow and heat transfer in reactive systems. However, there are considerable difficulties for accurate quantitative measurements due to beam hardening and radiation scattering effects. In a theoretical and experimental work we have investigated the non-linear effects of both physical phenomena and developed a suitable measurement setup as well as calibration and software correction methods to achieve a highly accurate measurement of void fraction profiles with CBCT.     

Minimally invasive osteosynthesis of fractures of the tibial head

The role of closed reduction techniques in tibial plateau fractures was evaluated retrospectively in a group of 33 patients. The patients had mainly B fractures (AO classification) and were treated by the arthroscopic reduction technique (n = 10) or by reduction under fluoroscopic control (n = 23) and transcutaneous screw fixation. The 21 patients with an average follow-up of 34 months (minimum 1 year) were reviewed. Using clinical and radiological criteria, 19 results were considered excellent to good. One patient with a residual deformity was revised with a total knee and 1 patient with an anatomical result had arthritic pain in the knee operated on. Arthroscopic reduction had no advantages over reduction under fluoroscopic control in this study. The specific value of the technically demanding endoscopic procedure should be questioned, as percutaneous reduction under fluoroscopic control may achieve comparable results in the majority of these cases.     

Smaller superconcentrators of density 28

An N-superconcentrator is a directed, acyclic graph with N input nodes and N output nodes such that every subset of the inputs and every subset of the outputs of same cardinality can be connected by node-disjoint paths. It is known that linear-size and bounded-degree superconcentrators exist. Here it is proved that such superconcentrators exist (by a random construction of certain expander graphs as building blocks) having density 28 (where the density is the number of edges divided by N). The best known density before this paper was 34.2 [U. Schöning, Construction of expanders and superconcentrators using Kolmogorov complexity, J. Random Structures Algorithms 17 (2000) 64-77] or 33 [L.A. Bassalygo, Personal communication, 2004].     

A note on a local twist estimator

For the construction of composite surfaces interpolating a given curve net a new local twist estimator was proposed recently (Farin and Hagen, 1992). Some properties of this estimator—including an explicit representation for Gaussian curvature K at the knots of the curve net—are presented in this note.     

Improving sub-pixel accuracy for long range stereo

Dense stereo algorithms are able to estimate disparities at all pixels including untextured regions. Typically these disparities are evaluated at integer disparity steps. A subsequent sub-pixel interpolation often fails to propagate smoothness constraints on a sub-pixel level.We propose to increase the sub-pixel accuracy in low-textured regions in four possible ways: First, we present an analysis that shows the benefit of evaluating the disparity space at fractional disparities. Second, we introduce a new disparity smoothing algorithm that preserves depth discontinuities and enforces smoothness on a sub-pixel level. Third, we present a novel stereo constraint (gravitational constraint) that assumes sorted disparity values in vertical direction and guides global algorithms to reduce false matches, especially in low-textured regions. Finally, we show how image sequence analysis improves stereo accuracy without explicitly performing tracking. Our goal in this work is to obtain an accurate 3D reconstruction. Large-scale 3D reconstruction will benefit heavily from these sub-pixel refinements.Results based on semi-global matching, obtained with the above mentioned algorithmic extensions are shown for the Middlebury stereo ground truth data sets. The presented improvements, called ImproveSubPix, turn out to be one of the top-performing algorithms when evaluating the set on a sub-pixel level while being computationally efficient. Additional results are presented for urban scenes. The four improvements are independent of the underlying type of stereo algorithm.     

Digital repository: preservation environment and policy implementation

Distributed digital repositories can be used to address critical issues of long-term digital preservation and disaster management for large data centers. A policy-driven system provides an ideal solution for managing distributed repositories that require high flexibility and high configurability. Recent studies demonstrate that the integrated Rule-Oriented Data System, a peer-to-peer server middleware, provides the requisite dynamic extensibility needed to manage time-varying policies, automate validation of assessment criteria, manage ingestion processes, manage access policies, and manage preservation policies. The policy management can be implemented underneath existing digital library infrastructure such as Fedora.     

Chord intercepts in a two-dimensional cell growth model

A foil of polypropylene is heat-treated in such a manner that a growing 2D cell-model is formed. A Rosiwal's line is placed into the totally primarily crystallized foil. The nucleus-coordinates of grains intercepting Rosiwal's line are measured. From these effective nuclei we determine at fraction transformedF = 1/4, 1/2 and 3/4 the distributions of grain-lengths and melt-lengths. Further we determine properties which are derived from the chord intercepts at a given F. Experimentally we find that the values (Poisson distribution of nuclei, chord intercepts, etc.) are in good agreement with the growing 2D cell-model.     

Topology of the moduli space for reachable linear dynamical systems: The complex case

This paper deals with the algebraic topology of the space _n,m of complex reachable linear dynamical systems. Topological invariants such as the singular homology groups of _n,m are explicitly computed and they are shown to coincide with those of a certain Grassmann manifold. From this some new results on the topology of rational transfer matrices with fixed McMillan degree are obtained.     

Energy Metabolites as Biomarkers in Ischemic and Dilated Cardiomyopathy

With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10⁻⁶). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets.     

From Natural Methylation to Versatile Alkylations Using Halide Methyltransferases

Halide methyltransferases (HMTs) enable the enzymatic synthesis of S-adenosyl-l -methionine (SAM) from S-adenosyl-l -homocysteine (SAH) and methyl iodide. Characterisation of a range of naturally occurring HMTs and subsequent protein engineering led to HMT variants capable of synthesising ethyl, propyl, and allyl analogues of SAM. Notably, HMTs do not depend on chemical synthesis of methionine analogues, as required by methionine adenosyltransferases (MATs). However, at the moment MATs have a much broader substrate scope than the HMTs. Herein we provide an overview of the discovery and engineering of promiscuous HMTs and how these strategies will pave the way towards a toolbox of HMT variants for versatile chemo- and regioselective biocatalytic alkylations.