Showing papers by "Technical University of Dortmund published in 1993"
TL;DR: This article defines outliers in terms of their position relative to the model for the good observations, in a sense derived from Donoho and Huber.
Abstract: One approach to identifying outliers is to assume that the outliers have a different distribution from the remaining observations. In this article we define outliers in terms of their position relative to the model for the good observations. The outlier identification problem is then the problem of identifying those observations that lie in a so-called outlier region. Methods based on robust statistics and outward testing are shown to have the highest possible breakdown points in a sense derived from Donoho and Huber. But a more detailed analysis shows that methods based on robust statistics perform better with respect to worst-case behavior. A concrete outlier identifier based on a suggestion of Hampel is given.
627 citations
01 Jan 1993
TL;DR: In this paper, the authors discuss applications and generalizations of the classical theorems of Helly, Radon, and Caratheodory, as well as their ramifications in the context of combinatorial convexity theory.
Abstract: This chapter discusses applications and generalizations of the classical theorems of Helly, Radon, and Caratheodory, as well as their ramifications in the context of combinatorial convexity theory. These theorems stand at the origin of what is known today as the combinatorial geometry of convex sets. Helly's theorem states that: letting K be a family of convex sets in ℝ d , and supposing K is finite or each member of K is compact; if every d + 1 or fewer members of K have a common point, then there is a point common to all members of K . Radon's theorem states that: letting X be a set of d + 2 or more points in ℝ d ; then X contains two disjoint subsets whose convex hulls have a common point. Caratheodory's theorem states that: letting X be a set in ℝ d and p a point in the convex hull of X . Then there is a subset Y of X consisting of d + 1 or fewer points such that p lies in the convex hull of Y .
298 citations
TL;DR: A measurement of the proton structure function F2 (x, Q2) was presented with about 1000 neutral current deep inelastic scattering events for Bjorken x in the range x ⋍ 10−2 − 10−4 and Q2 > 5 GeV2 as discussed by the authors.
228 citations
TL;DR: The complete [ital O]([alpha][alpha][sub [ital s]][sup 2]) corrections to the inclusive cross section for hadronic prompt photon production, both for the unpolarized case and for the case of longitudinal polarization for the incoming hadrons.
Abstract: We calculate the complete [ital O]([alpha][alpha][sub [ital s]][sup 2]) corrections to the inclusive cross section for hadronic prompt photon production, both for the unpolarized case and for the case of longitudinal polarization for the incoming hadrons. We present analytical expressions for all our results.
198 citations
TL;DR: It was found that upon deformation the dislocation density increases by about 2 orders of magnitude, providing the first direct evidence for quasicrystal deformation by a dislocation mechanism.
Abstract: Single quasicrystals of Al 7 0Pd 21 Mn 9 were plastically deformed by 25% under compression at 750 o C. Both these samples as well as control samples of as-grown and heat-treated material were investigated by transmission electron microscopy. It was found that upon deformation the dislocation density increases by about 2 orders of magnitude. This provides the first direct evidence for quasicrystal deformation by a dislocation mechanism. The dislocation were found to have twofold and fivefold Burgers vector directions in physical space
191 citations
01 Dec 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The liquid argon calorimeter of the H 1 detector presently taking data at the HERA ep collider at DESY, Hamburg, is described in this paper, where the main physics requirements and the most salient design features relevant to this calorometer are given.
Abstract: The liquid argon calorimeter of the H 1 detector presently taking data at the HERA ep collider at DESY, Hamburg, is described. The main physics requirements and the most salient design features relevant to this calorimeter are given. The aim to have smooth and hermetic calorimetric coverage over the polar angular range 4° ≤ θ ≤ 154° is achieved by a single liquid argon cryostat containing calorimeter stacks structured in wheels and octants for easy handling. The absorber materials used are lead in the electromagnetic part and stainless steel in the hadronic part. The read-out system is pipelined to reduce the dead time induced by the high trigger rate expected at the HERA collider where consecutive bunches are separated in time by 96 ns. The main elements of the calorimeter, such as the cryostat, with its associated cryogenics, the stack modules, the read-out, calibration and trigger electronics as well as the data acquisition system are described. Performance results from data taken in calibration runs with full size H 1 calorimeter stacks at a CERN test beam, as well as results from data collected with the complete H 1 detector using cosmic rays during the initial phase of ep operations are presented. The observed energy resolutions and linearities are well in agreement with the requirements.
156 citations
TL;DR: A protective effect of the glutathione-S-transferase activity in human erythrocytes for the cytogenetic toxicity of these chemicals in vitro is confirmed and species extrapolations for risk assessment of methyl bromide, ethylene oxide and dichloromethane should be reconsidered.
Abstract: A hitherto unknown glutathione-S-transferase in human erythrocytes displays polymorphism: three quarters of the population (“conjugators”) possess, whereas one quarter (“non-conjugators”) lack this specific activity. A standard method for the identification of conjugators and non-conjugators with the use of methyl bromide and gas chromatography (head space technique) is described. Three substrates of the polymorphic enzyme, methyl bromide, ethylene oxide and dichloromethane (methylene chloride), were incubated in vitro with individual whole blood samples of conjugators and non-conjugators. All three substances led to a marked increase of sister chromatid exchanges (SCE) in the lymphocytes of the non-conjugators but not in those of conjugators. A protective effect of the glutathione-S-transferase activity in human erythrocytes for the cytogenetic toxicity of these chemicals in vitro is thus confirmed. Since the enzyme activity is not found in erythrocytes of laboratory animals, species extrapolations for risk assessment of methyl bromide, ethylene oxide and dichloromethane should be reconsidered.
144 citations
École Polytechnique1, Slovak Academy of Sciences2, Centre national de la recherche scientifique3, RWTH Aachen University4, Max Planck Society5, Technical University of Dortmund6, University of Paris-Sud7, University of Glasgow8, University of Zurich9, Science and Engineering Research Council10, University of Hamburg11, University of California, Davis12, Queen Mary University of London13, Academy of Sciences of the Czech Republic14, Charles University in Prague15
01 Dec 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors present results on calibration runs performed with pions at the CERN SPS for different modules of the H 1 liquid argon calorimeter which consists of an electromagnetic section with lead absorbers and a hadronic section with steel absorbers.
Abstract: We present results on calibration runs performed with pions at the CERN SPS for different modules of the H 1 liquid argon calorimeter which consists of an electromagnetic section with lead absorbers and a hadronic section with steel absorbers. The data cover an energy range from 3.7 to 205 GeV. Detailed comparisons of the data and simulation with GHEISHA 8 in the framework of GEANT 3.14 are presented. The measured pion induced shower profiles are well described by the simulation. The total signal of pions on an energy scale determined from electron measurements is reproduced to better than 3% in various module configurations. After application of weighting functions, determined from Monte Carlo data and needed to achieve compensation, the reconstructed measured energies agree with simulation to about 3%. The energies of hadronic showers are reconstructed with a resolution of about 50% √E ⨸ 2% . This result is achieved by inclusion of signals from an iron streamer tube tail catcher behind the liquid argon stacks.
133 citations
21 Jun 1993
TL;DR: Based on this class of timed nets with timing of arcs directing from places to transitions, the corresponding state graph, called dynamic graph, and a method to compute the state graph are defined.
Abstract: The paper presents an analysis method for Place/Transition nets with timing of arcs directing from places to transitions. Based on this class of timed nets, the corresponding state graph, called dynamic graph, and a method to compute the state graph are defined.
126 citations
TL;DR: A theoretical framework is outlined, according to which structural constraints on bimanual movements can at least in part be understood as coupling between parameters of generalized motor programs.
Abstract: A theoretical framework is outlined, according to which structural constraints on bimanual movements can at least in part be understood as coupling between parameters of generalized motor programs. This framework provides a conceptual link between reaction-time data from experiments with bimanual responses, successive unimanual responses, and choice between left-hand and right-hand responses on the one hand and performance data obtained with concurrently performed continuous movements or sequences of discrete responses on the other. On the basis of data obtained with different methods for the study of intermanual interactions, a distinction is drawn between steady-state and transient constraints, and the hypothesis that the tendency to coactivate homologous muscles originates from a transient coupling of program parameters is applied to a variety of observations on performance in different tasks. Finally, the notion of transient constraints is applied to other types of intermanual interdependencies and to interpersonal coordination; the possible emergence of transient constraints from steady-state constraints through progressive development of inhibitory pathways in childhood is discussed, as is the potential biological significance of transient constraints.
119 citations
TL;DR: A new reduction algorithm which works in optimal linear time O(|G|) is presented, which is unique (up to isomorphisms) and can be computed from any OBDD G for f of size |G| in time O (¦G¦log¦ G¦).
TL;DR: In this paper, it was pointed out that the predictions of radiatively (dynamically) generated parton distributions are in satisfactory agreement with recent small-x measurements and moderate modifications of the valence-like input (mainly u ) remove possibly small discrepancies between experiment and theoretical predictions at x>10−2, but do not significantly affect the (steep) radiative predictions for x ≥ 10−2.
TL;DR: It is shown that ANNs can be much more powerful than traditional logic circuits, assuming that each threshold gate can be built with a cost that is comparable to that of AND/OR logic gates.
Abstract: An artificial neural network (ANN) is commonly modeled by a threshold circuit, a network of interconnected processing units called linear threshold gates. It is shown that ANNs can be much more powerful than traditional logic circuits, assuming that each threshold gate can be built with a cost that is comparable to that of AND/OR logic gates. In particular, the main results indicate that powering and division can be computed by polynomial-size ANNs of depth 4, and multiple product can be computed by polynomial-size ANNs of depth 5. Moreover, using the techniques developed, a previous result can be improved by showing that the sorting of n n-bit numbers can be carried out in a depth-3 polynomial-size ANN. Furthermore, it is shown that the sorting network is optimal in depth. >
TL;DR: In this article, the authors studied the photonic production via deep inelastic quark and gluon fragmentation in the framework of a specific factorization scheme chosen to provide the maximally possible amount of perturbative stability.
Abstract: Photon production via deep inelastic quark and gluon fragmentation is studied beyond the leading perturbative order within the framework of a specific factorization scheme ($\mathrm{DI}{\mathrm{S}}_{\ensuremath{\gamma}}$) chosen to provide the maximally possible amount of perturbative stability. It is argued that the perturbative (pointlike) results are expected to present a realistic estimate for photonic fragmentation functions, and the ambiguities related to the presently unknown, but possibly small, nonperturbative hadronic contributions are pointed out.
TL;DR: In this article, the mass of an additional W boson that couples to fermions with a V + A form is constrained to be greater than 261 GeV to the 90% confidence level, and a limit on the production cross section of additional W and Z bosons is given as a function of the boson mass.
TL;DR: This work develops the lowest nontrivial approximation for the one-band Hubbard Hamiltonian and applies it to the three-band Hamiltonian of the CuO superconductors, finding interesting results for the spectral density useful for the interpretation of photoemission experiments.
Abstract: The self-energy of a translational invariant system of interacting fermions may be expanded in diagrams contributing to the self-energy of finite clusters with open boundary conditions. The exact solution of small clusters might therefore be used to construct a systematic approximation to the self-energy of the infinite system. This approximation incorporates both the local and the itinerant degrees of freedom on an equal footing. We develop this method for the one-band Hubbard Hamiltonian and apply it to the three-band Hamiltonian of the CuO superconductors. Already the lowest nontrivial approximation yields interesting results for the spectral density useful for the interpretation of photoemission experiments. We find (i) transfer of spectral weight from the upper to the lower Hubbard band upon doping, (ii) the formation of an [ital isolated] band of Zhang-Rice singlets separated from the band of triplet states by a many-body gap, and (iii) creation of density of states [ital above] the top of the oxygen band upon doping.
TL;DR: The first results on the total photoproduction cross section measurement with the H1 detector at HERA were reported in this paper, where the data were extracted from low Q2 collisions of 26.7 GeV electrons with 820 GeV protons.
TL;DR: The results of both experiments show that estimates of time to contact are not uniquely determined by changing size, as seems to be implied by some tests of the so-called ‘tau hypothesis’, but that they are based on multiple sources of information that have situationally specific effects on the estimates.
Abstract: Apparent constant-velocity approaches of an outline circle were generated by changing the size and/or the lateral separation of dichoptically presented circles at a physically constant distance from subjects. The lateral separation of the circles defines target vergence which corresponds proximally to combinations of ocular vergence and (absolute) retinal disparity. In the first experiment, estimates of time to contact were found to depend both on changing size and on changing target vergence; in the case of conflicting information, changing size turned out to be the more powerful stimulus. In the second experiment, the size of the stimulus object was varied. The relatively stronger influence of changing size on estimates of time to contact was again found for the larger stimulus objects, but for the smaller stimulus objects changing target vergence became more powerful. The results of both experiments show that estimates of time to contact are not uniquely determined by changing size, as seems to be impl...
02 Jun 1993
TL;DR: In this paper, an example of a complex reaction system in a CSTR which leads to a nonlinear dynamic behavior with unstable zero dynamics is described in detail. And one particular control problem for this system is analyzed and solved using a novel combination of gain scheduling and linear frequency domain design techniques.
Abstract: Continuous stirred tank reactors (CSTRs) are central components of many plants in the chemical and biochemical industry. These systems may exhibit highly nonlinear dynamics, especially when consecutive and side reactions are present. In this paper, first an example of a complex reaction system in a CSTR which leads to a nonlinear dynamic behaviour with unstable zero dynamics is described in detail. Then one particular control problem for this system is analysed and solved using a novel combination of gain scheduling and linear frequency domain design techniques.
TL;DR: Results from DNA-binding studies and long-term inhalation bioassays argue in favor of a carcinogenic effect of methyl bromide in rodents, along with the proven systemic methylating potency of methyl iodide.
Abstract: Methyl chloride, bromide, and iodide are used as methylating agents. These compounds are mutagenic in short-term tests and do not require activation by exogenous S9 mix. In DNA-binding studies performed in rats and mice,14C-labeled methyl chloride was given by inhalation, and methylation of DNA bases was examined. The compound did not lead to specific DNA adducts. In particular, methylation of DNA bases was not observed. In contrast, methyl bromide and methyl iodide, upon oral and inhalation administration to rats and mice, caused systemic DNA methylation. Specifically, 3-methyl-adenine, 7-methyl-guanine, and O6- methyl-guanine were formed. Long-term inhalation bioassays have been performed in rats and mice with methyl chloride and methyl bromide. Methyl chloride induced renal tumors, but only in male mice at the highest concentration tested (1000 ppm). Under these special conditions, a number of secondary effects occur subsequent to glutathione depletion in the target tissue, resulting in DNA dam...
TL;DR: The results suggest a relation of the P-SR with stimulus evaluation (identification), and of theP-CR with response selection (stimulus-response mapping), and the results demonstrate the overlap of two positive waves in choice reaction tasks.
TL;DR: In this paper, a Titchmarsh-Weyl-coefficient for singular 8 hermitian systems of arbitrary deficiency index was defined, which is related to our singular selfadjoint problem.
Abstract: In part I of this work we defined a Titchmarsh-Weyl-coefficient M(λ) for singular 8 hermitian systems of arbitrary deficiency index. This construction proceeded by the method of von Noumann for selfadjoint extensions of symmetric operators. In this part we show how a Titchmarsh-Weyl coefficient M(λ) defined by a limit of Titchmarsh-Weyl coefficients on compact intervals is related to our M(λ). Examples are given in the intermediate deficiency index case which show that put all limits of Titchmarsh - Weyl coefficients on compact intervals give rise to a singular selfadjoint problem.
01 Aug 1993
TL;DR: A new method for designing learning algorithms: dynamic partitioning of the domain by use of splitting trees is introduced and it can be shown that the resulting lower bounds for learning ND are tight to within a logarithmic factor.
Abstract: Given a p-concept classC, we define two important functionsdC(�),d�C(�) (related to the notion of�-shattering). We prove a lower bound of�((dC(�)�1)/(��2)) on the number of examples required for learningCwith an (�,��)-good model of probability. We prove similar lower bounds for some other learning models like learning with�-bounded absolute (or quadratic) difference or learning with a�-good decision rule. For the class ND of nondecreasing p-concepts on the real domain,dND(�)=�(1/�). It can be shown that the resulting lower bounds for learning ND (within the models in consideration) are tight to within a logarithmic factor. In order to get the “almost-matching” upper bounds, we introduce a new method for designing learning algorithms: dynamic partitioning of the domain by use of splitting trees. The paper also contains a discussion of the gaps between the general lower bounds and the corresponding general upper bounds. It can be shown that, under very mild conditions, these gaps are quite narrow.
TL;DR: An algorithm for generating pure triangular or pure quadrilateral meshes for arbitrary polygonal domains is presented and two simple strategies are shown which can easily be implemented into any existing triangulation algorithm.
Abstract: In this paper an algorithm for generating pure triangular or pure quadrilateral meshes for arbitrary polygonal domains is presented. The first part shows a triangulation procedure being as suitable for local mesh refinement as for local mesh coarsening. In the second part an algorithm for transformation of triangular grids to quadrilateral meshes of the same relative mesh density is introduced. Two simple strategies are shown which can easily be implemented into any existing triangulation algorithm.
TL;DR: In this article, a relatively busy road with a load of 3200 vehicles per day has since 1961 run through the Aplerbecker Forest near the town of Dortmund in West Germany, and the soil in the forest was examined for the metals arsenic, cadmium, chromium, copper, lead, mercury, nickel, vanadium, zinc and fifteen polynuclear aromatic hydrocarbons (EPA).
TL;DR: Total-reflection X-ray fluorescence (TXRF) is a universal and economic method for the simultaneous determination of elements with atomic numbers > 11 down to the lower pg-level as mentioned in this paper.
TL;DR: In this paper, the authors analyzed the problem of harmonizing public debt and public pension schemes in a multi-jurisdictional setting and found that harmonization seems to be necessary on efficiency grounds if households can freely migrate between the jurisdictions.
Abstract: We analyze the problem of harmonizing public debt and public pension schemes in a multi-jurisdictional setting. Our main findings are that harmonization seems to be necessary on efficiency grounds if households can freely migrate between the jurisdictions. On the other hand, harmonization is unnecessary if households are immobile or if migration is prohibited on political grounds. This suggests that harmonization is an important issue for EC member states but not for, say, Japan or the United States.
TL;DR: In this paper, a direct search for new particles in the H1 experiment at HERA was presented for masses ranging from 35 GeV up to ∼ 250 GeV, and the data sample of 24 nb −1 accumulated during the first year of operation was analysed for signatures of scalar and vector leptoquarks, leptogluons, excited electrons and excited neutrinos with flavors of the first generation.
TL;DR: In this paper, an integrated-optic ammonia sensor based on evanescent-field absorption is presented, which is a strip waveguide, fabricated by field-assisted ion exchange, coated with an immobilized indicator dye.
Abstract: Fibre-coupled optical sensors for chemical and biological species are important for process control, environmental control and pollution detection, for example. Here, we report on an integrated-optic ammonia sensor, which is based on evanescent-field absorption. The sensitive element of this sensor is a strip waveguide, fabricated by field-assisted ion-exchange, coated with an immobilized indicator dye. The sensor has a short response time and long lifetime. We describe the experimental arrangement that has been built up for the characterization of different integrated-optic sensor elements. Spectral response characteristics, response times and the generation of reference signals are reported in detail. Furthermore, we show the simple temperature dependence, the humidity independence and the very low cross-sensitivity of this ammonia sensor.
TL;DR: In this article, the authors used the ARGUS detector at the e+e− storage ring DORIS II at DESY to detect a new charmed baryon state in the channel Λc+π+π−.