TY - JOUR A1 - Pena, M. A1 - Hamann, Wolf-Rainer A1 - Ruiz, M. T. A1 - Peimbert, A. A1 - Peimbert, M. T1 - A high resolution spectroscopic study of the extraordinary planetary nebula LMC-N66 N2 - The planetary nebula N66 in the Large Magellanic Cloud is an extraordinary object, as it is the only confirmed PN where the central star is a Wolf-Rayet star of the nitrogen sequence, i.e. of type [WN]. Moreover, the star showed a dramatic brightness outburst in 1993-1994. In a previous paper (Hamann et al. 2003) we analyzed the changing stellar spectra and found evidence that the central star is most likely a binary system where a white dwarf presently accretes matter from a non-degenerate companion at a high rate. Thus the object is a candidate for a future type Ia supernova in our cosmic neighborhood. In the present paper we analyze the morphology and kinematics of the nebula, using images and high-resolution spectra obtained with the Hubble Space Telescope (HST) and the Very Large Telescope (ESO-VLT). The object presents a complex multipolar structure, dominated by very bright lobes located at both sides of the central star and separated by a narrow waist. In addition there is a pair of very extended and twisted loops, also pointing in opposite directions; their symmetry axis and collimation angle differs from those of the bright lobes. High resolution spectroscopy reveals two main velocity components, "approaching" material at an average heliocentric radial velocity Of V-rad = 248 30 km s(-1) and similarly bright "receding" material at V-rad = 331 +/- 25 km s(-1). A systemic velocity of about 300 km s(-1) is derived. Opposite lobes and loops possess opposite velocities. Furthermore there are knots and filaments of complex structure and kinematics. Close to the central star, nebular gas is found, receding at very high velocity (125 km s(-1) relative to the system). The morphology and kinematics of LMC-N66 can be explained as the result of episodic bipolar ejections with changing axis. The bipolar structures could have been produced by collimated streams ejected from a precessing central source. We suggest that the precession could have been produced by an external torque, possibly due to a binary companion. Young, fast-moving nebular knots close to the star appear slightly He- and N-richer than the main body of the nebula, but are still hydrogen-rich in contrast to the helium-dominated atmosphere of the [WN]- type central star. In the binary scenario, this nebular matter must have been accreted from the non-degenerate companion and re-ejected before it was fully burnt Y1 - 2004 ER - TY - JOUR A1 - Kling, Christoph A1 - Schneidenbach, Lars A1 - Schnor, Bettina T1 - A high performance gigabit ethernet messaging method for PVFS N2 - Parallel File Systems like PVFS2 are a necessary compo nent for high-performance computing. The design of ef ;cient communication layers for these systems is still of great research interest. This paper presents a low- latency messaging method for PVFS2 dedicated for Gigabit Ether net networks and discusses relevant design issues. In con trast to other approaches, we argue that zero-copying can be achieved also for big messages without use of a rendez vous protocol. Further, ef;ciency within the communica tion layer like a small call stack plays an important role. Y1 - 2005 SN - 0-88986-525-6 ER - TY - JOUR A1 - Fischer, Martin H. T1 - A hierarchical view of grounded, embodied, and situated numerical cognition JF - Cognitive processing : international quarterly of cognitive science N2 - There is much recent interest in the idea that we represent our knowledge together with the sensory and motor features that were activated during its acquisition. This paper reviews the evidence for such "embodiment" in the domain of numerical cognition, a traditional stronghold of abstract theories of knowledge representation. The focus is on spatial-numerical associations, such as the SNARC effect (small numbers are associated with left space, larger numbers with right space). Using empirical evidence from behavioral research, I first describe sensory and motor biases induced by SNARC, thus identifying numbers as embodied concepts. Next, I propose a hierarchical relationship between grounded, embodied, and situated aspects of number knowledge. This hierarchical conceptualization helps to understand the variety of SNARC-related findings and yields testable predictions about numerical cognition. I report several such tests, ranging from cross-cultural comparisons of horizontal and vertical SNARC effects (Shaki and Fischer in J Exp Psychol Hum Percept Perform 38(3): 804-809, 2012) to motor cortical activation studies in adults with left- and right-hand counting preferences (Tschentscher et al. in NeuroImage 59: 3139-3148, 2012). It is concluded that the diagnostic features for each level of the proposed hierarchical knowledge representation, together with the spatial associations of numbers, make the domain of numerical knowledge an ideal testing ground for embodied cognition research. KW - Embodied cognition KW - Grounded cognition KW - Numerical cognition KW - SNARC effect Y1 - 2012 U6 - https://doi.org/10.1007/s10339-012-0477-5 SN - 1612-4782 VL - 13 SP - S161 EP - S164 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Cheng, Fuxia A1 - Hartmann, Stefanie A1 - Gupta, Mayetri A1 - Ibrahim, Joseph G. A1 - Vision, Todd J. T1 - A hierarchical model for incomplete alignments in phylogenetic inference N2 - Motivation: Full-length DNA and protein sequences that span the entire length of a gene are ideally used for multiple sequence alignments (MSAs) and the subsequent inference of their relationships. Frequently, however, MSAs contain a substantial amount of missing data. For example, expressed sequence tags (ESTs), which are partial sequences of expressed genes, are the predominant source of sequence data for many organisms. The patterns of missing data typical for EST-derived alignments greatly compromise the accuracy of estimated phylogenies. Results: We present a statistical method for inferring phylogenetic trees from EST-based incomplete MSA data. We propose a class of hierarchical models for modeling pairwise distances between the sequences, and develop a fully Bayesian approach for estimation of the model parameters. Once the distance matrix is estimated, the phylogenetic tree may be constructed by applying neighbor-joining (or any other algorithm of choice). We also show that maximizing the marginal likelihood from the Bayesian approach yields similar results to a pro. le likelihood estimation. The proposed methods are illustrated using simulated protein families, for which the true phylogeny is known, and one real protein family. Y1 - 2009 UR - http://bioinformatics.oxfordjournals.org/ U6 - https://doi.org/10.1093/bioinformatics/btp015 SN - 1367-4803 ER - TY - JOUR A1 - Fischer, Eric W. A1 - Werther, Michael A1 - Bouakline, Foudhil A1 - Saalfrank, Peter T1 - A hierarchical effective mode approach to phonon-driven multilevel vibrational relaxation dynamics at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - We discuss an efficient Hierarchical Effective Mode (HEM) representation of a high-dimensional harmonic oscillator bath, which describes phonon-driven vibrational relaxation of an adsorbate-surface system, namely, deuterium adsorbed on Si(100). Starting from the original Hamiltonian of the adsorbate-surface system, the HEM representation is constructed via iterative orthogonal transformations, which are efficiently implemented with Householder matrices. The detailed description of the HEM representation and its construction are given in the second quantization representation. The hierarchical nature of this representation allows access to the exact quantum dynamics of the adsorbate-surface system over finite time intervals, controllable via the truncation order of the hierarchy. To study the convergence properties of the effective mode representation, we solve the time-dependent Schrodinger equation of the truncated system-bath HEM Hamiltonian, with the help of the multilayer extension of the Multiconfigurational Time-Dependent Hartree (ML-MCTDH) method. The results of the HEM representation are compared with those obtained with a quantum-mechanical tier-model. The convergence of the HEM representation with respect to the truncation order of the hierarchy is discussed for different initial conditions of the adsorbate-surface system. The combination of the HEM representation with the ML-MCTDH method provides information on the time evolution of the system (adsorbate) and multiple effective modes of the bath (surface). This permits insight into mechanisms of vibration-phonon coupling of the adsorbate-surface system, as well as inter-mode couplings of the effective bath. Y1 - 2020 U6 - https://doi.org/10.1063/5.0017716 SN - 0021-9606 SN - 1089-7690 VL - 153 IS - 6 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Strohe, Hans Gerhard T1 - A heuristic partial-least-squares approach to estimating dynamic path models JF - Classification, Data Analysis, and Data Highways T2 - Proceedings of the 21st Annual Conference of the Gesellschaft für Klassifikation e.V., University of Potsdam, March 12-14, 1997 Y1 - 1998 SN - 3-540-63909-8 U6 - https://doi.org/10.1007/978-3-642-72087-1 PB - Springer CY - Berlin, Heidelberg ER - TY - JOUR A1 - Katterle, Martin A1 - Holzwarth, Alfred R. A1 - Jesorka, Aldo T1 - A Heck-type coupling for the synthesis of novel bridged metallochlorin-fullerene C-60 dyads N2 - A short and convenient synthesis of metallochlorin-C-60 dyads based on a Heck-type hetero coupling at the 3(2) position of a chlorin is described. p-Bromobenzaldehyde was treated with Zn-metalated 13(2)- demethoxycarbonylmethylpheophorbide a, using a palladium acetate/LiCl catalyst mixture under phase-transfer conditions in DMF at 70 degrees C. The resulting asymmetric olefin was obtained in a high trans/cis ratio. The desired trans isomer was separated and subsequently transformed into a donor-acceptor dyad by a 1,3-dipolar cycloaddition to C-60 in the presence of sarcosine in refluxing toluene. The resulting dyads are expected to undergo efficient photoinduced electron transfer and can potentially be utilized in solar energy conversion devices. Y1 - 2006 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/27380/ U6 - https://doi.org/10.1002/ejoc.200500494 SN - 1434-193X ER - TY - JOUR A1 - Anders, Jakob A1 - Mefenza, Michael A1 - Bobda, Christophe A1 - Yonga, Franck A1 - Aklah, Zeyad A1 - Gunn, Kevin T1 - A hardware/software prototyping system for driving assistance investigations JF - Journal of real-time image processing N2 - A holistic design and verification environment to investigate driving assistance systems is presented, with an emphasis on system-on-chip architectures for video applications. Starting with an executable specification of a driving assistance application, subsequent transformations are performed across different levels of abstraction until the final implementation is achieved. The hardware/software partitioning is facilitated through the integration of OpenCV and SystemC in the same design environment, as well as OpenCV and Linux in the run-time system. We built a rapid prototyping, FPGA-based camera system, which allows designs to be explored and evaluated in realistic conditions. Using lane departure and the corresponding performance speedup, we show that our platform reduces the design time, while improving the verification efforts. KW - System on chip KW - Prototyping KW - Hardware/software system KW - Image processing KW - Design flow KW - Driver assistance KW - FPGA KW - Hardware acceleration Y1 - 2016 U6 - https://doi.org/10.1007/s11554-013-0351-4 SN - 1861-8200 SN - 1861-8219 VL - 11 SP - 559 EP - 569 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Fahle, Marcus A1 - Dietrich, Ottfried A1 - Lischeid, Gunnar T1 - A guideline for developing an initial hydrological monotoring network as a basis for water management in artificially drained wetlands JF - Irrigation and drainage N2 - Reliable hydrological monitoring is the basis for sound water management in drained wetlands. Since statistical methods cannot be employed for unobserved or sparsely monitored areas, the primary design (first set-up) may be arbitrary in most instances. The objective of this paper is therefore to provide a guideline for designing the initial hydrological monitoring network. A scheme is developed that handles different parts of monitoring and hydrometry in wetlands, focusing on the positioning of surface water and groundwater gauges. For placement of the former, control units are used which correspond to areas whose water levels can be regulated separately. The latter are arranged depending on hydrological response units, defined by combinations of soil type and land use, and the chosen surface water monitoring sites. A practical application of the approach is shown for an investigation area in the Spreewald region in north-east Germany. The presented scheme leaves a certain degree of freedom to its user, allowing the inclusion of expert knowledge or special concerns. Based on easily obtainable data, the developed hydrological network serves as a first step in the iterative procedure of monitoring network optimisation. Copyright (c) 2013 John Wiley & Sons, Ltd. KW - monitoring network KW - wetland KW - sampling locations KW - controlled drainage KW - ditch system KW - measurement frequency Y1 - 2013 U6 - https://doi.org/10.1002/ird.1744 SN - 1531-0353 SN - 1531-0361 VL - 62 IS - 4 SP - 524 EP - 536 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Hartlieb, Matthias A1 - Mansfield, Edward D. H. A1 - Perrier, Sebastien T1 - A guide to supramolecular polymerizations JF - Polymer Chemistry N2 - Supramolecular polymers or fibers are non-covalent assemblies of unimeric building blocks connected by secondary interactions such as hydrogen bonds or pi-pi interactions. Such structures hold enormous potential in the development of future materials, as their non-covalent nature makes them highly modular and adaptive. Within this review we aim to provide a broad overview over the area of linear supramolecular polymers including the different mechanisms of their polymerization as well as methods essential for their characterization. The different non-covalent interactions able to form supramolecular polymers are discussed, and key examples for each species are shown. Particular emphasis is laid on the development of living supramolecular polymerization able to produce fibers with a controlled length and low length dispersity, and even enable the production of supramolecular block copolymers. Another important and very recent field is the development of out-of-equilibrium supramolecular polymers, where the polymerization process can be temporally controlled enabling access to highly adaptive materials. Y1 - 2020 U6 - https://doi.org/10.1039/c9py01342c SN - 1759-9954 SN - 1759-9962 VL - 11 IS - 6 SP - 1083 EP - 1110 PB - Royal Society of Chemistry CY - Cambridge ER -