The Alternate Arm Converter: A New Hybrid Multilevel Converter With DC-Fault Blocking Capability

This paper explains the working principles, supported by simulation results, of a new converter topology intended for HVDC applications, called the alternate arm converter (AAC). It is a hybrid between the modular multilevel converter, because of the presence of H-bridge cells, and the two-level converter, in the form of director switches in each arm. This converter is able to generate a multilevel ac voltage and since its stacks of cells consist of H-bridge cells instead of half-bridge cells, they are able to generate higher ac voltage than the dc terminal voltage. This allows the AAC to operate at an optimal point, called the “sweet spot,” where the ac and dc energy flows equal. The director switches in the AAC are responsible for alternating the conduction period of each arm, leading to a significant reduction in the number of cells in the stacks. Furthermore, the AAC can keep control of the current in the phase reactor even in case of a dc-side fault and support the ac grid, through a STATCOM mode. Simulation results and loss calculations are presented in this paper in order to support the claimed features of the AAC

Pastorale Begeleiding van die Emosioneel Verwonde Tiener

Many teenagers struggle with the consequences of emotional injuries. Simultaneously they are moving through the difficult phase of adolescence which may complicate their situation. In this article the first focus is the typical factors which compound the difficulties in this phase. Secondly we focus on a variety of possible causes of emotional injury. The results and consequences of such injuries form the third issue investigated. In the last instance attention is given to some pastoral-theological points of departure concerning  counselling of emotionally injured young people. To these young people their frame of reference is influenced by amongst other things their families,  school, church and friends. To experience real meaning in life the teenager’s relationship with God has to be healed, for this relationship determines all  other inter-personal relationships. The spiritual deepening accompanying this process often also significantly contributes to the eventual handling of  unprocessed hurt from the past

Recent Pangolin Seizures in China Reveal Priority Areas for Intervention

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Chiral zero-mode for abelian BPS dipoles

We present an exact normalisable zero-energy chiral fermion solution for abelian BPS dipoles. For a single dipole, this solution is contained within the high temperature limit of the SU(2) caloron with non-trivial holonomy.Comment: 9 pages, 1 figure (in 2 parts), presented at the workshop on "Confinement, Topology, and other Non-Perturbative Aspects of QCD", 21-27 Jan. 2002, Stara Lesna, Slovaki

Loop expansion in Yang-Mills thermodynamics

We argue that a selfconsistent spatial coarse-graining, which involves interacting (anti)calorons of unit topological charge modulus, implies that real-time loop expansions of thermodynamical quantities in the deconfining phase of SU(2) and SU(3) Yang-Mills thermodynamics are, modulo 1PI resummations, determined by a finite number of connected bubble diagrams.Comment: 15 pages, 2 figures, v5: discussion of much more severely constrained nonplanar situation included in Sec.

Photosynthesis dependent acidification of perialgal vacuoles in theParamedum bursaria/Chlorella symbiosis. Visualization by monensin

After treatment with the carboxylic ionophore monensin theChlorella containing perialgal vacuoles of the greenParamecium bursaria swell. TheParamecium cells remain motile at this concentration for at least one day. The swelling is only observed in illuminated cells and can be inhibited by DCMU. We assume that during photosynthesis the perialgal vacuoles are acidified and that monensin exchanges H+ ions against monovalent cations (here K+). In consequence the osmotic value of the vacuoles increases. The proton gradient is believed to drive the transport of maltose from the symbiont into the host. Another but light independent effect of the monensin treatment is the swelling of peripheral alveoles of the ciliates, likewise indicating that the alveolar membrane contains an active proton pump

Context based mixture model for cell phase identification in automated fluorescence microscopy

BACKGROUND: Automated identification of cell cycle phases of individual live cells in a large population captured via automated fluorescence microscopy technique is important for cancer drug discovery and cell cycle studies. Time-lapse fluorescence microscopy images provide an important method to study the cell cycle process under different conditions of perturbation. Existing methods are limited in dealing with such time-lapse data sets while manual analysis is not feasible. This paper presents statistical data analysis and statistical pattern recognition to perform this task. RESULTS: The data is generated from Hela H2B GFP cells imaged during a 2-day period with images acquired 15 minutes apart using an automated time-lapse fluorescence microscopy. The patterns are described with four kinds of features, including twelve general features, Haralick texture features, Zernike moment features, and wavelet features. To generate a new set of features with more discriminate power, the commonly used feature reduction techniques are used, which include Principle Component Analysis (PCA), Linear Discriminant Analysis (LDA), Maximum Margin Criterion (MMC), Stepwise Discriminate Analysis based Feature Selection (SDAFS), and Genetic Algorithm based Feature Selection (GAFS). Then, we propose a Context Based Mixture Model (CBMM) for dealing with the time-series cell sequence information and compare it to other traditional classifiers: Support Vector Machine (SVM), Neural Network (NN), and K-Nearest Neighbor (KNN). Being a standard practice in machine learning, we systematically compare the performance of a number of common feature reduction techniques and classifiers to select an optimal combination of a feature reduction technique and a classifier. A cellular database containing 100 manually labelled subsequence is built for evaluating the performance of the classifiers. The generalization error is estimated using the cross validation technique. The experimental results show that CBMM outperforms all other classifies in identifying prophase and has the best overall performance. CONCLUSION: The application of feature reduction techniques can improve the prediction accuracy significantly. CBMM can effectively utilize the contextual information and has the best overall performance when combined with any of the previously mentioned feature reduction techniques

Slightly generalized Generalized Contagion: Unifying simple models of biological and social spreading

We motivate and explore the basic features of generalized contagion, a model mechanism that unifies fundamental models of biological and social contagion. Generalized contagion builds on the elementary observation that spreading and contagion of all kinds involve some form of system memory. We discuss the three main classes of systems that generalized contagion affords, resembling: simple biological contagion; critical mass contagion of social phenomena; and an intermediate, and explosive, vanishing critical mass contagion. We also present a simple explanation of the global spreading condition in the context of a small seed of infected individuals.Comment: 8 pages, 5 figures; chapter to appear in "Spreading Dynamics in Social Systems"; Eds. Sune Lehmann and Yong-Yeol Ahn, Springer Natur

Morphologic grading of emphysema is useful in the selection of candidates for unilateral or bilateral reduction pneumoplasty

Objective: Radiologic morphology of emphysema proves useful in the selection of candidates for bilateral reduction pneumoplasty. We developed a simple morphologic grading system capable of identifying subsets of patients who had maximal functional improvement after unilateral or bilateral operation. Methods: Fifty-two patients who underwent unilateral (n = 34) or bilateral (n = 18) reduction pneumoplasty were evaluated. Emphysema morphology was visually scored by digital roentgenograms and high-resolution computed tomography. In each lung, severity of emphysema (ES), heterogeneity (DHT) and hyperinflation (DHF) degrees, were assessed. Asymmetric ratio of emphysema (ARE) between the lungs was expressed as: higher ES/lower ES scores. Morphometric data were correlated with absolute preoperative-postoperative FEV1 change (Delta FEV1). Results: No difference was found between the unilateral and the bilateral group for ES and DHT. DHF was greater in the bilateral group (3.1 vs. 2.7, P = 0.02) whereas ARE was greater in the unilateral group (1.29 vs. 1.05, P = 0.0001). Stepwise logistic regression extracted as best predictors of maximal Delta FEV1, ARE (odds ratio = 238, Wald test P = 0.04) in the unilateral group, and DHT (odds ratio = 24, P = 0.03) in the bilateral group. Unilateral group Delta FEV1 was greater in patients with ARE greater than or equal to 1.3 (0.44 vs. 0.241, P = 0.02). Bilateral group Delta FEV1 was greater in patients with DEET > 1 (0.50 vs. 0.31 1, P = 0.03). No difference was found when comparing Delta FEV1 resulting from unilateral RP and ARE greater than or equal to 1.3, and bilateral RP (0.44 vs. 0.41 1, not significant). Conclusions: This morphologic grading system identified subsets of patients who had maximal functional benefit from unilateral or bilateral reduction pneumoplasty and might be useful in the preoperative screening of candidates for either approach. (C) 2000 Published by Elsevier Science B.V

Linear and star architecture methacrylate-functionalised PDMS

Methacrylate-terminated poly(dimethylsiloxane)s in both linear and star architectures have been produced through a time-efficient 1 pot, 2 stage reaction which involved hydrosilylation of small molecule silanes with allyl methacrylate and subsequent equilibration of the product with octamethylcyclotetrasiloxane (D4) in the presence of an acid catalyst. This synthetic route required only one work-up procedure and the products were comparable to those produced by 2 step processes typically reported in literature. All methacrylate-terminated products were approximately double the molar masses anticipated based on reagent loadings. This is thought to be due to redistribution of siloxane bonds in the presence of the platinum hydrosilylation catalyst accompanied by a loss of silicon from the reaction by evaporation of dimethylsilane. It is believed that this is the first report of such siloxane equilibration occurring at room temperature