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Showing papers by "Technical University of Berlin published in 2006"


Journal ArticleDOI
TL;DR: In this paper, the FLASH soft X-ray free-electron laser was used to reconstruct a coherent diffraction pattern from a nano-structured nonperiodic object, before destroying it at 60,000 K.
Abstract: Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x 10{sup 13} W/cm{sup 2} pulse, containing 10{sup 12} photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano-structured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling, shows no measurable damage, and extends to diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one.

957 citations


Journal ArticleDOI
01 Jul 2006-Energy
TL;DR: In this article, a systematic and general methodology for defining and calculating exergetic efficiencies and exergy related costs in thermal systems is proposed, based on the Specific Exergy Costing (SPECO) approach, in which fuel and product of a component are defined by taking a systematic record of all exergy additions to and removals from all the exergy streams of the system, and the costs are calculated by applying basic principles from business administration.

877 citations


Journal ArticleDOI
08 Dec 2006-Science
TL;DR: The application of gTME is shown to Saccharomyces cerevisiae for improved glucose/ethanol tolerance, a key trait for many biofuels programs.
Abstract: Global transcription machinery engineering (gTME) is an approach for reprogramming gene transcription to elicit cellular phenotypes important for technological applications. Here we show the application of gTME to Saccharomyces cerevisiae for improved glucose/ethanol tolerance, a key trait for many biofuels programs. Mutagenesis of the transcription factor Spt15p and selection led to dominant mutations that conferred increased tolerance and more efficient glucose conversion to ethanol. The desired phenotype results from the combined effect of three separate mutations in the SPT15 gene [serine substituted for phenylalanine (Phe(177)Ser) and, similarly, Tyr(195)His, and Lys(218)Arg]. Thus, gTME can provide a route to complex phenotypes that are not readily accessible by traditional methods.

826 citations


Journal ArticleDOI
03 Nov 2006-Science
TL;DR: Polarized extended x-ray absorption fine structure measurements on PSII single crystals constrain the Mn4Ca cluster geometry to a set of three similar high-resolution structures, unlike either the 3.0 or 3.5 angstrom–resolution x-rays or other previously proposed models.
Abstract: The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn4Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn4Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom–resolution x-ray structures or other previously proposed models.

761 citations


Journal ArticleDOI
TL;DR: The overall structural diversity of cyanobacterial oligopeptides only seemingly suggests an equally high diversity of biosynthetic pathways and respective genes, which implies that non-ribosomal peptide synthetase genes are a very ancient part of the cyanob bacterial genome and presumably have evolved by recombination and duplication events to reach the present structural diversity.
Abstract: Cyanobacterial secondary metabolites have attracted increasing scientific interest due to bioactivity of many compounds in various test systems. Among the known structures, oligopeptides are often found with many congeners sharing conserved substructures, while being highly variable in others. A major part of known oligopeptides are of non-ribosomal origin and can be grouped into classes with conserved structural properties. Thus, the overall structural diversity of cyanobacterial oligopeptides only seemingly suggests an equally high diversity of biosynthetic pathways and respective genes. For each class of peptides, some of which have been found in all major branches of the cyanobacterial evolutionary tree, homologous synthetases and genes can be inferred. This implies that non-ribosomal peptide synthetase genes are a very ancient part of the cyanobacterial genome and presumably have evolved by recombination and duplication events to reach the present structural diversity of cyanobacterial oligopeptides. In addition, peptide synthetases would appear to be an essential part of the cyanobacterial evolution and physiology. The present review presents an overview of the biosynthesis of cyanobacterial peptides and corresponding gene clusters, the structural diversity of structural types and structural variations within peptide classes, and implications for the evolution and plasticity of biosynthetic genes and the potential function of cyanobacterial peptides.

706 citations


Journal ArticleDOI
TL;DR: This paper presents the most significant contributions of the past decade, which produce such impressive and perceivably realistic animations and simulations: finite element/difference/volume methods, mass‐spring systems, mesh‐free methods, coupled particle systems and reduced deformable models‐based on modal analysis.
Abstract: Physically based deformable models have been widely embraced by the Computer Graphics community. Many problems outlined in a previous survey by Gibson and Mirtich [ GM97] have been addressed, thereby making these models interesting and useful for both offline and real-time applications, such as motion pictures and video games. In this paper, we present the most significant contributions of the past decade, which produce such impressive and perceivably realistic animations and simulations: finite element/difference/volume methods, mass-spring systems, meshfree methods, coupled particle systems and reduced deformable models based on modal analysis. For completeness, we also make a connection to the simulation of other continua, such as fluids, gases and melting objects. Since time integration is inherent to all simulated phenomena, the general notion of time discretization is treated separately, while specifics are left to the respective models. Finally, we discuss areas of application, such as elastoplastic deformation and fracture, cloth and hair animation, virtual surgery simulation, interactive entertainment and fluid/smoke animation, and also suggest areas for future research.

636 citations


Journal ArticleDOI
TL;DR: The non-settable fraction of the sludges was found to impact fouling and to cause the difference in membrane performance between the two MBR, which point to microbiologically produced substances such as extracellular polymeric substances (EPS) or soluble microbial products (SMP).

564 citations


Journal ArticleDOI
TL;DR: In this article, the role of patenting and alternative instruments to protect intellectual property is analyzed against the background of the patent upsurge, based on a sample of German companies active in patenting.

556 citations


Journal ArticleDOI
TL;DR: The hydration- and temperature-dependent dynamic behavior of graphite oxide will be investigated by quasielastic neutron scattering using the time-of-flight spectrometer NEAT at the Hahn-Meitner-Institut Berlin.
Abstract: Graphite oxide is an inorganic multilayer system that preserves the layered structure of graphite but not the conjugated bond structure. In the past few years, detailed studies of the static structure of graphite oxide were carried out. This was mainly done by NMR investigations and led to a new structural model of graphite oxide. The layer distance of graphite oxide increases with increasing humidity level, giving rise to different spacings of the carbon layers in the range from 6 to 12 A. As a consequence, different types of motions of water and functional groups appear. Information about the mobility of the water molecules is not yet complete but is crucial for the understanding of the structure of the carbon layers as well as the intercalation process. In this paper, the hydration- and temperature-dependent dynamic behavior of graphite oxide will be investigated by quasielastic neutron scattering using the time-of-flight spectrometer NEAT at the Hahn-Meitner-Institut Berlin. The character of the embed...

520 citations


Journal ArticleDOI
TL;DR: In this paper, the authors identify characteristics of users who contribute substantially to the development of radical innovations by being their inventors and (co-developers, and observe that they play an entrepreneurial role as they establish and organize the required innovation networks.
Abstract: This paper focuses on contributions of users in early phases of radical innovation projects. In a multiple case study analysis in the field of medical equipment technology, we identify characteristics of users who contribute substantially to the development of radical innovations by being their inventors and (co)-developers. These innovative users have high motivation to seek new solutions, possess a diverse set of competencies, and are embedded in a supportive environment. We furthermore observe that they play an entrepreneurial role as they establish and organize the required innovation networks. These innovation networks are needed to transform the users' radically new concepts into first physical prototypes and marketable products. The study highlights how manufacturing firms can benefit from innovative and entrepreneurial users in the early phases of radical innovation projects.

471 citations


Journal ArticleDOI
TL;DR: It is proposed that this index provides a measure for the potential of a polar compound to spread along a partially closed water cycle after discharge with municipal wastewater and to occur in raw waters used for drinking water production.
Abstract: The effluents of eight municipal wastewater treatment plants (WWTP) in Western Europe were analyzed by liquid-chromatography−mass spectrometry for the occurrence of 36 polar pollutants, comprising household and industrial chemicals, pharmaceuticals, and personal care products. In a long-term study of the effluents of three WWTP over 10 months, sulfophenyl carboxylates and ethylene diamino tetraacetate (EDTA) were detected above 10 μg/L on average, while benzotriazoles, benzothiazole-2-sulfonate, diclofenac, and carbamazepine showed mean concentrations of 1−10 μg/L, followed by some flame retardants, naphthalene disulfonates, and personal care products in the range of 0.1−1 μg/L. Half of the determined compounds were not significantly removed in tertiary wastewater treatment. By dividing the effluent concentration of a compound by its relative removal in WWTP a water cycle spreading index (WCSI) was calculated for each compound. We propose that this index provides a measure for the potential of a polar com...

Journal ArticleDOI
TL;DR: In this paper, the correlation between the internal structure and dynamics of polyelectrolyte multilayers and their functional properties was investigated and different concepts of multilayer formation like driving forces, adsorption kinetics, mode of growth and stability aspects were considered.
Abstract: The paper deals with the correlation between the internal structure and dynamics of polyelectrolyte multilayers on one hand and their functional properties on the other hand. It considers different concepts of multilayer formation like driving forces, adsorption kinetics, mode of growth and stability aspects. A further focus is the control of internal structure and dynamics which is of high impact with respect to the design of stimuli-responsive material.

Journal ArticleDOI
TL;DR: The application of emerging, novel processing techniques such as high hydrostatic pressure or pulsed electric fields can be utilized to replace, enhance or modify conventional techniques of food production as discussed by the authors.
Abstract: The application of emerging, novel processing techniques such as high hydrostatic pressure or pulsed electric fields can be utilized to replace, enhance or modify conventional techniques of food production. In addition to quality improvements and consumer benefits by gentle microbial inactivation and improvement of mass transfer processes, their potential to improve energy efficiency and sustainability of food production will be discussed within this review.

Journal ArticleDOI
TL;DR: In this paper, the authors present an overview of the current state of the art in modeling and simulation of grinding processes: physical process models (analytical and numerical models) and empirical process models(regression analysis, artificial neural net models) as well as rule based models (rule based models) are taken into account.

Journal ArticleDOI
TL;DR: The current research involves the study of the thermal treatment of quercetin and rutin in an aqueous model system (cooking), which showed strong degradation of the model substances took place under weak basic and oxidative conditions.
Abstract: The current research involves the study of the thermal treatment of quercetin and rutin in an aqueous model system (cooking). These substances were heated and their degradation was followed by high-performance liquid chromatography/diode-array detection (HPLC/DAD). The influence of pH and the involvement of oxygen in the degradation were studied. HPLC/electrospray ionization multi-stage mass spectrometry (ESI-MS(n)) was used for the structural characterization of the compounds produced. The influence of the degradation of the phenolic compounds on their antioxidant properties was elucidated by a electron spin resonance (ESR) spectrometry study of the reaction samples mixed with the stabilized radical, Fremy's salt. Strong degradation of the model substances took place under weak basic and oxidative conditions. Quercetin showed the most intense degradation. Protocatechuic acid could be identified as a cleavage reaction product by analyzing its retention time and molar mass during the degradation of quercetin. The structure of a second cleavage product could be identified on the basis of ESI-MS(n) fragmentation data. Also, several structures for reaction products of oxidized quercetin are suggested. The ESR analysis showed a decrease in the antioxidant activity of the reaction samples after heat treatment in aqueous solution.

Journal ArticleDOI
TL;DR: This work develops a systematic approach to generating large classes of linearizations for a matrix polynomial, and shows how to simply construct two vector spaces of pencils that generalize the companion forms of $P, and proves that almost all of these pencils are linearized for $P$.
Abstract: The classical approach to investigating polynomial eigenvalue problems is linearization, where the polynomial is converted into a larger matrix pencil with the same eigenvalues. For any polynomial there are infinitely many linearizations with widely varying properties, but in practice the companion forms are typically used. However, these companion forms are not always entirely satisfactory, and linearizations with special properties may sometimes be required. Given a matrix polynomial $P$, we develop a systematic approach to generating large classes of linearizations for $P$. We show how to simply construct two vector spaces of pencils that generalize the companion forms of $P$, and prove that almost all of these pencils are linearizations for $P$. Eigenvectors of these pencils are shown to be closely related to those of $P$. A distinguished subspace is then isolated, and the special properties of these pencils are investigated. These spaces of pencils provide a convenient arena in which to look for structured linearizations of structured polynomials, as well as to try to optimize the conditioning of linearizations.

Journal ArticleDOI
TL;DR: Cassette mutagenesis combined with advanced mass spectrometric techniques revealed that the pks1 (bae) and pks3 (dif) gene clusters encode the biosynthesis of the polyene antibiotics bacillaene and difficid in or oxydifficidin, respectively.
Abstract: Although bacterial polyketides are of considerable biomedical interest, the molecular biology of polyketide biosynthesis in Bacillus spp., one of the richest bacterial sources of bioactive natural products, remains largely unexplored. Here we assign for the first time complete polyketide synthase (PKS) gene clusters to Bacillus antibiotics. Three giant modular PKS systems of the trans-acyltransferase type were identified in Bacillus amyloliquefaciens FZB 42. One of them, pks1, is an ortholog of the pksX operon with a previously unknown function in the sequenced model strain Bacillus subtilis 168, while the pks2 and pks3 clusters are novel gene clusters. Cassette mutagenesis combined with advanced mass spectrometric techniques such as matrix-assisted laser desorption ionization-time of flight mass spectrometry and liquid chromatography-electrospray ionization mass spectrometry revealed that the pks1 (bae) and pks3 (dif) gene clusters encode the biosynthesis of the polyene antibiotics bacillaene and difficidin or oxydifficidin, respectively. In addition, B. subtilis OKB105 (pheA sfp0), a transformant of the B. subtilis 168 derivative JH642, was shown to produce bacillaene, demonstrating that the pksX gene cluster directs the synthesis of that polyketide.

Proceedings ArticleDOI
29 Nov 2006
TL;DR: This work introduces a framework for triangle shape optimization and feature preserving smoothing of triangular meshes that is guided by the vertex Laplacian and the discrete mean curvature normal, and it is capable of smoothing the surface while preserving geometric features.
Abstract: We introduce a framework for triangle shape optimization and feature preserving smoothing of triangular meshes that is guided by the vertex Laplacians, specifically, the uniformly weighted Laplacian and the discrete mean curvature normal. Vertices are relocated so that they approximate prescribed Laplacians and positions in a weighted least-squares sense; the resulting linear system leads to an efficient, non-iterative solution. We provide different weighting schemes and demonstrate the effectiveness of the framework on a number of detailed and highly irregular meshes; our technique successfully improves the quality of the triangulation while remaining faithful to the original surface geometry, and it is also capable of smoothing the surface while preserving geometric features.

Proceedings ArticleDOI
26 May 2006
TL;DR: The self-configuration capability, the use of hardware with standardized interfaces and open-source software makes the TWIST architecture scalable, affordable, and easily repli-cable.
Abstract: We present TWIST, a scalable and exible testbed architecture for indoor deployment of wireless sensor networks. The design of TWIST is based on an analysis of typical and desirable use-cases. It provides basic services like node configuration, network-wide programming, out-of-band extraction of debug data and gathering of application data, and also introduces several novel features.Firstly, TWIST supports experiments with heterogeneous node platforms. Secondly, it supports active power supply control of the nodes. This enables easy transition between USB-powered and battery-powered experiments, dynamic selection of topologies as well as controlled injection of node failures into the system. Thirdly, TWIST supports creation of both at and hierarchical sensor networks. For this we introduce a layer of "super nodes" that on one hand form a part of the testbed infrastructure but can also play a role as elements of the sensor network.The self-configuration capability, the use of hardware with standardized interfaces and open-source software makes the TWIST architecture scalable, affordable, and easily repli-cable. To demonstrate its usefulness, we present our experiences with building and using a specific realization of TWIST that spans three floors of our office building and supports over one hundred sensor nodes.

Journal ArticleDOI
TL;DR: The synthesis of a novel divalent silicon compound by debromination of the corresponding dibromosilyl precursor is reported, and addition of Me3SiX to the silylene furnishes the corresponding 1,4-adduct which subsequently rearranges to the thermodynamically favored 1,1- adduct.
Abstract: The synthesis of a novel divalent silicon compound by debromination of the corresponding dibromosilyl precursor is reported. The silylene possesses a unique reactivity toward electrophiles of the type R−X (R = H, silyl; X = halogen, triflate) in comparison with the germanium congener. DFT calculations suggest that this is due to a much higher basicity of the silylene versus that of germylene lone-pair electrons. Thus, addition of Me3SiX to the silylene (X = OSO2CF3, triflate) furnishes the corresponding (kinetically favored) 1,4-adduct which subsequently rearranges to the thermodynamically favored 1,1-adduct.

Journal ArticleDOI
TL;DR: Data is presented on the effects of high hydrostatic pressure in combination with temperature on protein stability, enzymatic activity and starch gelatinization and attention is given to the protein thermodynamics in response to combined pressure and temperature treatments.

Journal ArticleDOI
TL;DR: This paper analyzes the existence and uniqueness of a special class of linearizations which reflect the structure of structured polynomials, and therefore preserve symmetries in their spectra, and shows how they may be systematically constructed.
Abstract: Many applications give rise to nonlinear eigenvalue problems with an underlying structured matrix polynomial. In this paper several useful classes of structured polynomials (e.g., palindromic, even, odd) are identified and the relationships between them explored. A special class of linearizations which reflect the structure of these polynomials, and therefore preserve symmetries in their spectra, is introduced and investigated. We analyze the existence and uniqueness of such linearizations and show how they may be systematically constructed.

Journal ArticleDOI
TL;DR: The experimental results show that FARMS with default parameters outperforms previous methods if both sensitivity and specificity are simultaneously considered by the area under the receiver operating curve (AUC).
Abstract: Motivation: We propose a new model-based technique for summarizing high-density oligonucleotide array data at probe level for Affymetrix GeneChips. The new summarization method is based on a factor analysis model for which a Bayesian maximum a posteriori method optimizes the model parameters under the assumption of Gaussian measurement noise. Thereafter, the RNA concentration is estimated from the model. In contrast to previous methods our new method called 'Factor Analysis for Robust Microarray Summarization (FARMS)' supplies both P-values indicating interesting information and signal intensity values. Results: We compare FARMS on Affymetrix's spike-in and Gene Logic's dilution data to established algorithms like Affymetrix Microarray Suite (MAS) 5.0, Model Based Expression Index (MBEI), Robust Multi-array Average (RMA). Further, we compared FARMS with 43 other methods via the 'Affycomp II' competition. The experimental results show that FARMS with default parameters outperforms previous methods if both sensitivity and specificity are simultaneously considered by the area under the receiver operating curve (AUC). We measured two quantities through the AUC: correctly detected expression changes versus wrongly detected (fold change) and correctly detected significantly different expressed genes in two sets of arrays versus wrongly detected (P-value). Furthermore FARMS is computationally less expensive then RMA, MAS and MBEI. Availability: The FARMS R package is available from http://www.bioinf.jku.at/software/farms/farms.html Contact: hochreit@bioinf.jku.at Supplementary information: http://www.bioinf.jku.at/publications/papers/farms/supplementary.ps

Proceedings ArticleDOI
25 Jun 2006
TL;DR: This paper provides an overview of dimensionality reduction techniques, placing the emphasis on the kind of distance relation preserved, and shows how the GP-LVM can be generalized, through back constraints, to additionally preserve local distances.
Abstract: The Gaussian process latent variable model (GP-LVM) is a generative approach to nonlinear low dimensional embedding, that provides a smooth probabilistic mapping from latent to data space. It is also a non-linear generalization of probabilistic PCA (PPCA) (Tipping & Bishop, 1999). While most approaches to non-linear dimensionality methods focus on preserving local distances in data space, the GP-LVM focusses on exactly the opposite. Being a smooth mapping from latent to data space, it focusses on keeping things apart in latent space that are far apart in data space. In this paper we first provide an overview of dimensionality reduction techniques, placing the emphasis on the kind of distance relation preserved. We then show how the GP-LVM can be generalized, through back constraints, to additionally preserve local distances. We give illustrative experiments on common data sets.

MonographDOI
01 Jun 2006
TL;DR: The Gibbsian formalism and metastates, a generalised version of Derrida's generalised random energy models, and the SK models and the Parisi solution, which solve the number partitioning problem.
Abstract: Preface Part I. Statistical Mechanics: 1. Introduction 2. Principles of statistical mechanics 3. Lattice gases and spin systems 4. Gibbsian formalism 5. Cluster expansions Part II. Disordered Systems: Lattice Models: 6. Gibbsian formalism and metastates 7. The random field Ising model Part III: Disordered Systems: Mean Field Models: 8. Disordered mean field models 9. The random energy model 10. Derrida's generalised random energy models 11. The SK models and the Parisi solution 12. Hopfield models 13. The number partitioning problem Bibliography Index of notation Index.

Journal ArticleDOI
TL;DR: In this article, the authors classified various methods for making liquid metal foams with respect to the mode of gas generation and the type of melt used for foaming, and found that although stabilisation seems to be based on the presence of a solid constituent in all the foaming processes, the mechanisms might vary.
Abstract: Liquid metal foam can be generated by creating gas inside a liquid or semi-liquid metallic melt which has been pre-treated in a suitable way. Such foams are self-supporting disordered structures in complete analogy to aqueous foams. The stabilisation mechanism of metallic foams is still not fully understood. In order to facilitate discussion of foam stabilisation the various methods for making such foams are classified with respect to the mode of gas generation and the type of melt used for foaming. Metal foams can be produced by gas injection from an external source or by in-situ nucleation of gas bubbles in the melt for which various possibilities are known. Melts amenable to foaming range from almost pure molten alloys to melts to which particles have been added, formed by in-situ reactions or which have been already present in the solid precursor prior to melting. Some of the available experimental evidence for the action of stabilising particles in metallic foams is presented. It is found that although stabilisation seems to be based on the presence of a solid constituent in all the foaming processes, the mechanisms might vary. At present the nature of stabilisation is not yet fully understood and many questions remain

Journal ArticleDOI
TL;DR: The detailed characterization of the yeast promoter collection comprising 11 mutants of the strong constitutive Saccharomyces cerevisiae TEF1 promoter is provided, allowing detailed genotype-phenotype characterizations.
Abstract: The strong overexpression or complete deletion of a gene gives only limited information about its control over a certain phenotype or pathway. Gene function studies based on these methods are therefore incomplete. To effect facile manipulation of gene expression across a full continuum of possible expression levels, we recently created a library of mutant promoters. Here, we provide the detailed characterization of our yeast promoter collection comprising 11 mutants of the strong constitutive Saccharomyces cerevisiae TEF1 promoter. The activities of the mutant promoters range between about 8% and 120% of the activity of the unmutated TEF1 promoter. The differences in reporter gene expression in the 11 mutants were independent of the carbon source used, and real-time PCR confirmed that these differences were due to varying levels of transcription (i.e., caused by varying promoter strengths). In addition to a CEN/ARS plasmid-based promoter collection, we also created promoter replacement cassettes. They enable genomic integration of our mutant promoter collection upstream of any given yeast gene, allowing detailed genotype-phenotype characterizations. To illustrate the utility of the method, the GPD1 promoter of S. cerevisiae was replaced by five TEF1 promoter mutants of different strengths, which allowed analysis of the impact of glycerol 3-phosphate dehydrogenase activity on the glycerol yield.

Journal ArticleDOI
TL;DR: In this paper, a second-order kinetic model was proposed to predict ozone decomposition in wastewater, showing that TOD is not a suitable parameter for the prediction of disinfection or oxidation in wastewater.
Abstract: The decomposition of ozone in wastewater is observed starting 350 milliseconds after ozone addition. It seems not to be controlled by the autocatalytic chain reaction, but rather by direct reactions with reactive moieties of the dissolved organic matter (DOM). A larger ozone dose increases ozone consumption prior to 350 milliseconds but decreases the rate of ozone decomposition later on; this effect is predicted by a second-order kinetic model. Transferred Ozone Dose (TOD) is poorly correlated with ozone exposure (= ∫[O3]dt) indicating that TOD is not a suitable parameter for the prediction of disinfection or oxidation in wastewater. HO• concentrations (> 10−10 M) and Rct (=∫[HO•]dt/∫[O3]dt > 10−6) are larger than in most advanced oxidation processes (AOP) in natural waters, but rapidly decrease over time. Rct also decreases with increasing pre-ozonation doses. An increase in pH accelerates ozone decomposition and HO• generation; this effect is predicted by a kinetic model taking into account deprotonatio...


Journal ArticleDOI
TL;DR: A novel method for the construction of discrete conformal mappings from surface meshes of arbitrary topology to the plane based on circle patterns, that is, arrangements of circles---one for each face---with prescribed intersection angles, which supports very flexible boundary conditions ranging from free boundaries to control of the boundary shape via prescribed curvatures.
Abstract: We introduce a novel method for the construction of discrete conformal mappings from surface meshes of arbitrary topology to the plane. Our approach is based on circle patterns, that is, arrangements of circles---one for each face---with prescribed intersection angles. Given these angles, the circle radii follow as the unique minimizer of a convex energy. The method supports very flexible boundary conditions ranging from free boundaries to control of the boundary shape via prescribed curvatures. Closed meshes of genus zero can be parameterized over the sphere. To parameterize higher genus meshes, we introduce cone singularities at designated vertices. The parameter domain is then a piecewise Euclidean surface. Cone singularities can also help to reduce the often very large area distortion of global conformal maps to moderate levels. Our method involves two optimization problems: a quadratic program and the unconstrained minimization of the circle pattern energy. The latter is a convex function of logarithmic radius variables with simple explicit expressions for gradient and Hessian. We demonstrate the versatility and performance of our algorithm with a variety of examples.