Showing papers by "Technical University of Dortmund published in 1995"
TL;DR: In this article, the perturbative properties of parton distributions generated radiatively from a valence-like input at some low resolution scale are discussed with the aim of explaining the physical aspects underlying the reliability of the predicted distributions in the small-x region.
Abstract: The perturbative properties of parton distributions generated radiatively from a valence-like input at some low resolution scale are discussed with the aim of explaining the physical aspects underlying the reliability of the predicted distributions in the small-x region. Aspects of higher-twist (shadowing) effects as well as small-x resummations are discussed. Utilizing recent improved data atx≳10−2 and a factorization scheme in which the heavy quarksc, b, ..., arenot entailed among the intrinsic (massless) parton distributions, we readjust our valencelike input and provide parametrizations of the slightly modified dynamical LO and NLO\((\overline {MS} ,DIS)\) predictions for parton distributions.
654 citations
TL;DR: Using two-photon absorption under hydrostatic pressure up to 7.3 GPa at a temperature of 6 K, this paper determined the pressure dependences of the three lowest energy band gaps in the wurtzite semiconductor ZnO.
461 citations
TL;DR: In this paper, it was shown that CP-violation in the Majorana mass matrices of the heavy neutrinos can generate a CP-asymmetric universe, and that during the electroweak phase transition the lepton asymmetry is converted into a baryon asymmetry, which survives down to this time.
399 citations
TL;DR: Jacobs and Bock as mentioned in this paper showed that γ-Fe4N crystallizes in the CaTiO3 (perovskite) structure type: X-ray single-crystal diffractometer data, space group Pm3m, Z=1 and a=3.0170.
234 citations
TL;DR: An N2 effect was found after visual but not after auditory stimuli, which is evidence against the response-inhibition hypothesis.
221 citations
TL;DR: In this paper, a measurement of the contribution of diffractive interactions to deep-inelastic electron-proton (ep) scattering in the kinematic range 8.5 × 10−4 < Bjorken-x < 0.0133, and 3.7 × 10 −4 < χp <0.043.
163 citations
TL;DR: In this article, a measurement of the proton structure function was reported for momentum transfer squared Q^2 between 4.5 GeV^2 and 1600 GeV+2 and for Bjorken x between 1.8\cdot10^{-4} and 0.13 using data collected by HERA experiment H1 in 1993.
158 citations
TL;DR: It is shown that the observed oscillations are evidence for memory effects, and provides a first test of the central ideas of quantum kinetics, in which the effects of quantum coherence and of dissipation are intrinsically connected.
Abstract: Oscillations of the transient four-wave-mixing signal with a period of about $100\mathrm{fs}$ are observed in bulk GaAs using 14 fs pulses tuned to the exciton resonance at low temperatures. The measurements are explained in terms of the non-Markovian quantum kinetics for electron-hole pairs due to LO-phonon scattering. It is shown that the observed oscillations are evidence for memory effects. The experiments provide a first test of the central ideas of quantum kinetics, in which the effects of quantum coherence and of dissipation are intrinsically connected.
147 citations
124 citations
TL;DR: Two new generalized models of graph driven BDDs are presented and many other functions can be represented in small polynomial size in this model and the usual operations on OBDDs can be performed efficiently also for graph drivenBDDs.
121 citations
TL;DR: It is shown that every k—uniform hypergraph ℋ on n vertices with average degree ik-1 containing no 2—cycles has independence number α(ℋ)≧ck n/t(lnt)1/(k-1) for t ≧ t0(k).
Abstract: In this note we will show that every k—uniform hypergraph ℋ on n vertices with average degree ik-1 containing no 2—cycles has independence number α(ℋ)≧ck n/t(lnt)1/(k-1) for t ≧ t0(k). This confirms a conjecture of Spencer. © 1995 John Wiley & Sons, Inc.
TL;DR: In this study, robust build and parameters associated with good anaerobic capacity were the most powerful individual characteristics contributing to the smallest drop in the power output with the fire-protective clothing system and SCBA.
Abstract: Every fire fighter needs to wear fire-protective clothing and a self-contained breathing apparatus (SCBA) several times a year while carrying out various fire-fighting and rescue operations in hazardous work environments. The aim of the present study was to quantify the effects of a multilayer turnout suit designed to fulfil European standard EN 469 used over standardized (Nordic) clothing and with SCBA (total mass 25.9 kg) on maximal physical work performance, and to evaluate the relationship between individual characteristics and power output with the fire-protective clothing system and SCBA. The subjects were 12 healthy firemen aged 26–46 years. The range of their body mass, body fat and maximal oxygen consumption was 69–101 kg, 10–20% and 2.70–5.86 1·min−1, respectively. The maximal tests without (control) and with the fire-protective clothing system and SCBA were carried out on a treadmill in a thermoneutral environment. When compared to the control test, the decrease in the maximal power output in terms of maximal working time and walking speed averaged 25% (P < 0.001) varying from 18% to 34% with the fire-protective clothing system and SCBA. At maximum, no significant differences were found in pulmonary ventilation, absolute oxygen consumption, the respiratory exchange ratio, heart rate, systolic blood pressure, the rate-pressure product, mechanical efficiency, and the rating of perceived exertion between the tests with and without the fire-protective clothing system and SCBA. The reduction of the power output was related to the extra mass of the fire protective clothing and SCBA. In this study, robust build and parameters associated with good anaerobic capacity were the most powerful individual characteristics contributing to the smallest drop in the power output with the fire-protective clothing system and SCBA. All possible means to decrease the mass of both the fire-protective clothing system and SCBA for maintaining the sufficient power output in physically demanding fire-fighting and rescue tasks need to be considered.
TL;DR: Hierarchical Markovian models are a useful paradigm for the specification and quantitative analysis of models arising from complex systems and can be integrated in an appropriate modelling tool environment for the analysis of hierarchical models and often yields a dramatic reduction in the state space size.
TL;DR: In this paper, a model for the structure of the quasi-crystals, based on a zonohedral tiling of the Penrose local isomorphism class with four different unit cells, is discussed.
TL;DR: It has now been demonstrated that the background rate for sister chromatid exchange (SCE) is affected by this particular polymorphism of glutathione S-transferase θ, and hypothesized that GSTT1 is protective against background genotoxic damage.
Abstract: Polymorphism of glutathione S-transferase θ (GSTT1) modulates the toxicity of halogenated alkanes and epoxides in humans. The enzymatic activity of glutathione S-transferase θ and its corresponding gene is lacking in about 30% of the central European population. It has now been demonstrated that the background rate for sister chromatid exchange (SCE) is affected by this particular polymorphism. Smoking as a known inducer of SCE was taken into account. A group of GSTT1-positive subjects exhibited lower SCE rates than GSTT1-negative individuals (7.55±0.77 versus 8.74±1.24 SCE/mitosis, respectively, p<0.005). Non-smoking GSTT1-positive individuals showed the lowest SCE rate (7.26±0.71 SCE/mitosis), significantly lower than the rates of smoking GSTT1-positive and non-smoking GSTT1-negative subjects (8.14±0.55 SCE/mitosis and 8.12±0.88 SCE/mitosis, respectively, p<0.025 in both cases). Smoking GSTT1-negative subjects exhibited the highest SCE rates (9.28±1.3 SCE/mitosis). It is hypothesized that GSTT1 is protective against background genotoxic damage. Since ethylene oxide is a proven substrate of GSTT1, the detoxification of this epoxide arising from endogenous ethylene may modulate SCE background rates.
TL;DR: Results indicate that OTA is genotoxic in this in vitro system, which represents the urinary bladder epithelium, a target organ of OTA in vivo, and it could also be shown that OT-alpha, which is said to be non-toxic, is genotinic in this assay at higher concentrations.
Abstract: The mycotoxin ochratoxin A (OTA) and its metabolite ochratoxin alpha (OT-alpha) were investigated, to examine their potency to induce sister chromatid exchages (SCE) in cultured poricine urinary baldder epithedial cells (PUBEC) (primary cluture). Serum-free cultured PUBEC were incubated for 5 h with either OTA or OT-alpha, respectively, and subsequently cutured in the presence of 5-bromo-2-deoxyuridine (BrdU). After two cell cycles, mitosis was inhibited by the colchicine derivative Colcemid, cells were fixed and chromosomes were prepared for SCE analysis. For OTA, a dose-dependent increase in SCE frequency was measured in concentrations between 100 pM and 100 nM OTA. At 100nM OTA, SCE frequency increased by about 41%, compared to the base SCE level (7.27 SCEs per chromosome set, solvent control). Higher concentrations of OTA were cytotoxic. The metabolite OT-alpha also increased SCE frequency, but at higher concentrations. At a concentration of 10μM OT-alpha, an increase of about 55% was detected. OT-alpha showed no cytotoxic effect. There results indicate that OTA is genotoxic in this in vitro system, which represents the urinary bladder epithelium, a target organ of OTA in vivo. It could also be shown that OT-alpha, which is said to be non-toxic, is genotoxic in this assay at higher concentrations.
TL;DR: In this paper, structural and bonding features of the amide ion in condensed phases in comparison to crystalline hydrates and hydroxides are discussed with respect to the structure and bonding properties of LiNH 2 and LiND 2.
TL;DR: In this article, the authors measured the production of transverse energy in deep inelastic scattering using the H1 detector at the ep collider HERA and compared the different predictions based upon two alternative QCD evolution equations, namely the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and the Balitsky-Fadin-Kuraev-Linatov (BFKL) equations.
TL;DR: This work warps the space surrounding the given shape with the effect of deforming the embedded shape, too, with a function derived with scattered data interpolation methods from the displacements of a finite set of control points that can be placed arbitrarily and adaptively.
12 Sep 1995
TL;DR: By adding a self-organizing acceptance threshold schedule to the proportionate reproduction operator it is proved that the algorithm converges to the global optimum.
Abstract: We present a genetic algorithm (GA) whose population possesses a spatial structure. The GA is formulated as a probabilistic cellular automaton: The individuals are distributed over a connected graph and the genetic operators are applied locally in some neighborhood of each individual. By adding a self-organizing acceptance threshold schedule to the proportionate reproduction operator we can prove that the algorithm converges to the global optimum. First results for a multiple knapsack problem indicate a significant improvement in convergence behavior. The algorithm can be mapped easily onto parallel computers.
TL;DR: In this paper, the authors derived the gluon distribution in the photon in the fractional momentum range 004 ⩽ xγ⩽ 1 at the average factorization scale 75 GeV2.
01 Jan 1995
TL;DR: Equivalence relations for stochastic automata are introduced such that an automaton in a network can be substituted by an equivalent and usually smaller automaton without affecting the results of an analysis.
Abstract: Stochastic Automata Networks (SANs) are an efficient means to describe and analyze parallel systems under Markovian assumptions. The main advantage of SANs is the possibility to describe and analyze a complex parallel system in a compositional way such that the transition matrix of the Markov chain underlying the complete SAN can be described in a compositional way using only small matrices specifying single automata and combine these matrices by means of tensor operations. This approach allows, up to a certain extent, the handling of the state space explosion resulting from complex Markov models. In this paper equivalence relations for stochastic automata are introduced such that an automaton in a network can be substituted by an equivalent and usually smaller automaton without affecting the results of an analysis. We consider equivalence according to stationary and transient analysis of SANs.
TL;DR: An integrated package of Parton Density Functions called PDFLIB has been added to the CERN Program Library Pool W999 and is labelled as W5051 and all the different sets of parton density functions which are available today have been put together.
Abstract: This article describes an integrated package of Parton Density Functions called PDFLIB which has been added to the CERN Program Library Pool W999 and is labelled as W5051. In this package all the different sets of parton density functions of the Nucleon, the Pion and the Photon which are available today have been put together. All these sets have been combined in a consistent way such that they all have similar calling sequences and no external data files have to be read in anymore. A default set has been prepared, although those preferring their own set or wanting to test a new one may do so within the package. The package also offers a program to calculate the strong coupling constant αs to first or second order. The correct ΛQCD associated to the selected set of structure functions and the number of allowed flavours with respect to the given Q2 is automatically used in the calculation. The selection of sets, the program parameters as well as the possibilities to modify the defaults and to control errors occurred during execution are described.
TL;DR: In this paper, a Grimm-type glow discharge source was compared by Langmuir probe measurements and by optical emission spectrometry, and the results confirmed that there is no local thermal equilibrium in the discharge plasma.
TL;DR: In this paper, a descriptive study was conducted to identify misconceptions held by German senior high school students about the Brsted acid-base theory, and test items were developed that can be used to uncover student problems in this area.
Abstract: The purpose of this descriptive study was to identify misconceptions held by German senior high school students about the Br⊘nsted acid‐‐base theory. Test items were developed that can be used to uncover student problems in this area. A sample of 4291 senior high school students in grades 11‐13 completed paper‐and‐pencil tests on acid‐‐base theory. Discussions in individual classes were videotaped while the students solved test questions. The results indicate that German senior high school students have two misconceptions about conjugate acid‐‐base pairs. First, they confuse non‐conjugate and conjugate acid‐‐base pairs. One possible explanation for this is that the distinction between the two associations is seldom mentioned in US and German chemistry textbooks. Second, students regard pairs of positively and negatively charged ions as conjugate acid‐‐base pairs as if they somehow neutralized each other. Students use chemical terminology, but misconceptions occur because the terminology is mislea...
TL;DR: In the Munker—White effect grey target bars appear lighter when they are flanked by white bars, and darker when they is flanked by black bars.
Abstract: In the Munker-White effect grey target bars appear lighter when they are flanked by white bars, and darker when they are flanked by black bars. It is shown that the effect is enhanced if the patterns are presented stereoscopically so that the grey bars appear either behind the grating, in which case they are seen as a rectangle that is occluded by the white bars of the grating, or in front of the grating, so that they form a transparent rectangle. These results are explained in terms of object perception: contrast enhances differences between an object and its surroundings, whereas assimilation reduces differences within an object.
TL;DR: In this article, a QCD analysis of the proton structure function F 2 measured by the H1 experiment at HERA, combined with data from previous fixed target experiments is presented, and the gluon density is extracted from the scaling violations of F 2 in the range 2 · 10 −4 x −2 and compared with an approximate solution of the QCD evolution equations.
13 Sep 1995
TL;DR: This paper proposes a novel approach to local code compaction based on an integer programming model, which obeys exact timing constraints, due to a general problem formulation that obeys encoding restrictions and possible side-effects.
Abstract: DSP algorithms are, in most cases, subject to hard real-time constraints. In the case of programmable DSPs, meeting those constraints must be ensured by appropriate code generation techniques. For processors offering instruction-level parallelism, the task of code generation includes code compaction. The exact timing behavior of a DSP program is only known after compaction. Therefore, real-time constraints should be taken into account during the compaction phase. While most known DSP code generators rely on rigid heuristics for that phase, this paper proposes a novel approach to local code compaction based on an integer programming model, which obeys exact timing constraints. Due to a general problem formulation, the model also obeys encoding restrictions and possible side-effects.
TL;DR: In this article, the results of experimental investigations of longitudinal flow and cross-flow tube-bundle heat-exchangers in bubble columns are presented and compared with empirical and semi-theoretical correlations.
Abstract: Indirect and direct heat transfer is an important aspect in the design of bubble column reactors used for many industrial organic and inorganic processes. Longitudinal flow or cross-flow tube-bundle heat-exchangers, jacket cooling, direct evaporative cooling or circulation cooling are possible methods for this purpose. The existing physical and empirical models describing heat transfer in bubble columns are reviewed. The results of experimental investigations of longitudinal-flow and cross-flow tube-bundle heat-exchangers in bubble columns are presented and compared with empirical and semi-theoretical correlations. In the second part of the article the governing equations describing heat transfer in gas/liquid bubble column reactors are derived under the assumptions of the axial dispersion model and the cell model with backflow. For steady-state conditions, the axial dispersion model leads to a boundary value problem consisting of non-linear ordinary differential equations, whereas the cell model with backflow can be represented by a system of non-linear algebraic equations. Both equation systems include strong non-linearities and can be solved only by special numerical methods. As an example of the use of heat-transfer correlations in modelling bubble columns, the wet air oxidation of municipal sewage sludge carried out in a three-phase bubble column reactor (18 m in height, 2 m in diameter) is simulated considering different heat-removal methods. The simulation runs were carried out with the BCR program, which was developed at the University of Dortmund and the UMSICHT institute for the simulation of bubble column reactors operated under industrial conditions.
TL;DR: In this paper, a leading order QCD analysis of spin asymmetries in polarized deep inelastic lepton scattering is presented within the framework of the radiative parton model, respecting the fundamental positivity constraints down to the low resolution scale Q 2 = μ LO 2 = 0.23 GeV 2.