Showing papers by "Bielefeld University published in 1997"
TL;DR: In this article, the medium-induced p⊥-broadening and induced gluon radiation spectrum of a high energy quark traversing a large nucleus is studied.
1,062 citations
TL;DR: In this article, the medium induced energy loss spectrum of a high energy quark or gluon traversing a hot QCD medium of finite volume is studied, where the interaction is modeled by a simple picture of static scattering centres.
907 citations
TL;DR: MMP-8 exerts markedly wider expression in human cells than had been thought previously, implying that PMN are not the only source of cartilage degrading activity at arthritic sites and provides an incentive for further studies on the clinical effects of doxycycline in the treatment of rheumatoid arthritis.
503 citations
TL;DR: The authors are concerned here with one of the oldest problems in combinatorial extremal theory, which is readily described after they have made a few conventions.
Abstract: We are concerned here with one of the oldest problems in combinatorial extremal theory. It is readily described after we have made a few conventions. ގ denotes the set of
380 citations
Uppsala University1, University of Warsaw2, Bielefeld University3, Max Planck Society4, CERN5, Paul Scherrer Institute6, University of Neuchâtel7, University of Padua8, University of Freiburg9, University of Geneva10, Yale University11, University of Mainz12, University of California, Santa Cruz13, University of Bonn14, Istituto Superiore di Sanità15, Osaka University16, Heidelberg University17, Stockholm University18, University of Erlangen-Nuremberg19, University of Mons20, Dresden University of Technology21, European Synchrotron Radiation Facility22, Warsaw University of Technology23
TL;DR: In this article, the muon-proton and muon deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q(2) < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV.
334 citations
TL;DR: The automated evaluation of strain‐specific fingerprint patterns has the potential to become a valuable tool for studies of bacterial population genetics and the rapid identification of single strains in epidemiological studies seems feasible.
Abstract: In a comparative study, the PCR-based RAPD and ERIC fingerprint methods were evaluated for their resolving power to discriminate among 21 isolates of a natural Rhizobium meliloti population. PCR fingerprint patterns were analysed by using an automated laser fluorescent (ALF) DNA sequencer, thus allowing the automated on-line storage of data. Results obtained were compared to a classification system using insertion sequence (IS) fingerprinting. Both PCR fingerprint methods were comparable in their ability to resolve differences amongst Rh. meliloti isolates. Grouping of strains on the basis of their RAPD as well as their ERIC fingerprints correlated with grouping of strains according to their IS fingerprints. Moreover, strains displaying identical PCR patterns could be further differentiated according to their IS fingerprints, thus allowing a detailed insight into phylogenetic relationship among strains. The automated evaluation of strain-specific fingerprint patterns has the potential to become a valuable tool for studies of bacterial population genetics. Moreover, the rapid identification of single strains, e.g. pathogens in epidemiological studies seems feasible.
196 citations
TL;DR: The terminology of the most recent algorithm, Ukkonen's on-line construction, is used to explain its historic predecessors, revealing relationships much closer than one would expect, since the three algorithms are based on rather different intuitive ideas.
Abstract: We review the linear-time suffix tree constructions by Weiner, McCreight, and Ukkonen. We use the terminology of the most recent algorithm, Ukkonen's on-line construction, to explain its historic predecessors. This reveals relationships much closer than one would expect, since the three algorithms are based on rather different intuitive ideas. Moreover, it completely explains the differences between these algorithms in terms of simplicity, efficiency, and implementation complexity.
179 citations
TL;DR: In this paper, a cross molecular beam study of the hydrogen exchange reaction in the H+D2→HD+D isotopic form at two collision energies: 0.53 and 1.28 eV was carried out.
Abstract: We have carried out a systematic crossed molecular beam study of the hydrogen exchange reaction in the H+D2→HD+D isotopic form at two collision energies: 0.53 and 1.28 eV. The Rydberg atom time-of-flight method was used to measure the D-atom product angle-velocity distribution. For the first time ro-vibrational quantum state resolved differential cross sections for the title reaction were measured, which can directly be compared to theoretical predictions at this detailed level. Experimental results are compared to theoretical predictions from both quasi classical and quantum mechanical calculations on different potential energy surfaces as well as to earlier experiments. A general good agreement is found for the converged quantum mechanical calculations with indications that the Boothroyd-Keogh-Martin-Peterson potential energy surface is better suited to describe the dynamics of the reaction. For the higher collision energy the quasi classical trajectory calculations reproduce the experimental data quite well, whereas they fail to describe the situation at the lower collision energy especially with respect to angular resolved differential cross sections.
159 citations
TL;DR: In this article, the authors study the onset of this change in terms of hadronic comover interactions and conclude that so far no conventional hadronic description can consistently account for all data.
Abstract: Data from J/ψ and ψ′ production in p - A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/ψ suppression in O - Cu, O - U and S - U collisions is fully reproduced by the corresponding nuclear absorption, while Pb - Pb collisions show an additional suppression increasing with centrality. We study the onset of this change in terms of hadronic comover interactions and conclude that so far no conventional hadronic description can consistently account for all data. Deconfinement, starting at a critical point determined by central S - U collisions, is in accord with the observed suppression pattern.
155 citations
TL;DR: In this paper, a lattice calculation of the masses of mesons with exotic quantum numbers is presented, where the quenched approximation partially suppresses this mixing, and the hybrid meson masses are large {emdash} over 4 GeV for charmonium and more than twice the vector meson mass at our smallest quark mass.
Abstract: Since gluons in QCD are interacting fundamental constituents just as quarks are, we expect that in addition to mesons made from a quark and an antiquark, there should also be glueballs and hybrids (bound states of quarks, antiquarks, and gluons). In general, these states would mix strongly with the conventional {bar q}q mesons. However, they can also have exotic quantum numbers inaccessible to {bar q}q mesons. Confirmation of such states would give information on the role of {open_quotes}dynamical{close_quotes} color in low energy QCD. In the quenched approximation we present a lattice calculation of the masses of mesons with exotic quantum numbers. These hybrid mesons can mix with four quark ({bar q}{bar q}qq) states. The quenched approximation partially suppresses this mixing. Nonetheless, our hybrid interpolating fields also couple to four quark states. Using a four-quark source operator, we demonstrate this mixing for the 1{sup {minus}+} meson. Using the conventional Wilson quark action, we calculate both at reasonably light quark masses, intending to extrapolate to small quark mass, and near the charmed quark mass, where we calculate the masses of some {bar c}cg hybrid mesons. The hybrid meson masses are large {emdash} over 4 GeV for charmonium and more than twice themore » vector meson mass at our smallest quark mass, which is near the strange quark mass. {copyright} {ital 1997} {ital The American Physical Society}« less
140 citations
TL;DR: A fast and complete method to enumerate fullerene structures is given based on a top-down approach, and it is fast enough to generate, for example, all 1812 isomers ofC60in less than 20 s on an SGI-workstation.
TL;DR: In this article, a new perturbative scheme is proposed for the evaluation of the free energy density of field theories at finite temperature, which takes into account exactly the phenomenon of screening in thermal propagators.
TL;DR: In this article, the authors analyse the properties of a simple "balls-in-boxes" model which can exhibit a phase transition between a fluid and a condensed phase, similar to the behaviour encountered in models of random geometries in one, two and four dimensions.
TL;DR: In this paper, a nonperturbative Floquet-Bloch theory of the interacting system (crystal plus laser field) is developed and applied to obtain the field-modified band structure of the system.
Abstract: Generation of high harmonics by the interaction of intense laser fields with periodic crystal structures is investigated theoretically. A nonperturbative Floquet-Bloch theory of the interacting system (crystal plus laser field) is developed and applied to obtain the field-modified band structure of the system. The mean energy spectrum, the dispersion and the fluctuation of the band energy in the photon space, and the associated standard deviation and spectral entropy are calculated. The harmonic generation spectra in a thin crystal, for the neodymium-doped yttrium aluminum garnet laser frequency $\ensuremath{\omega}=1.169$ eV, are obtained, both in the perturbative and nonperturbative intensity domains. The calculated emission spectra for an insulator, a semiconductor, and a metal film are compared. The semiconductor medium is found to be somewhat more efficient than the metal or the insulator. A ``transition intensity'' for strong harmonic generation in crystalline media occurs at about an intensity I=${10}^{\ensuremath{-}4}$ a.u., i.e., $3.51\ifmmode\times\else\texttimes\fi{}{10}^{12}$ W/cm${}^{2}$.
TL;DR: Proteins directing the biosynthesis of galactoglucan in Rhizobium meliloti Rm2011 are encoded by the exp genes, and operon analysis revealed that the exp gene cluster consists of five complementation groups.
Abstract: Proteins directing the biosynthesis of galactoglucan (exopolysaccharide II) in Rhizobium meliloti Rm2011 are encoded by the exp genes. Sequence analysis of a 32-kb DNA fragment of megaplasmid 2 containing the exp gene cluster identified previously (J. Glazebrook and G. C. Walker, Cell 56:661-672, 1989) revealed the presence of 25 open reading frames. Homologies of the deduced exp gene products to proteins of known function suggested that the exp genes encoded four proteins involved in the biosynthesis of dTDP-glucose and dTDP-rhamnose, six glycosyltransferases, an ABC transporter complex homologous to the subfamily of peptide and protein export complexes, and a protein homologous to Rhizobium NodO proteins. In addition, homologies of three Exp proteins to transcriptional regulators, methyltransferases, and periplasmic binding proteins were found. The positions of 26 Tn5 insertions in the exp gene cluster were determined, thus allowing the previously described genetic map to be correlated with the sequence. Operon analysis revealed that the exp gene cluster consists of five complementation groups. In comparison to the wild-type background, all exp complementation groups were transcribed at a substantially elevated level in the regulatory mucR mutant.
TL;DR: The authors compare the Big-Five factor structures found in Dutch, American English, and German, and present a joint structure, and assess congruences between the factors as originally published, as resulting from target rotations, and from simultaneous rotations.
Abstract: We compare Big-Five factor structures found in Dutch, American English, and German, and present a joint structure. The data consist of self- and peer ratings of 600 subjects with 551 Dutch trait-descriptive adjectives, 636 subjects with 540 English adjectives, and 802 subjects with 430 German adjectives. On the basis of 126 common items, we assess the congruences between the factors as originally published, as resulting from target rotations, and from simultaneous rotations. With the exception of the Dutch Factor V, the Big-Five factors recur across languages in a relative but not in a strict sense. Moreover, at a more detailed level differences in the positions of the axes are uncovered. By applying a split-sample technique to the three data sets, we verify that these differences do not arise through unreliability. Also, few trait terms appear to have the same precise meaning across these three languages; such labels therefore cannot serve as anchor concepts for an international language of personality. (C) 1997 by John Wiley & Sons, Ltd.
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06 Jan 1997TL;DR: From Two Republics to One Divided as mentioned in this paper examines Peru's troubled transition from colonial viceroyalty to post-colonial republic from the local perspective of Andean peasant politics and provides a critical revision of the meaning of the Atusparia Uprising of 1885.
Abstract: From Two Republics to One Divided examines Peru’s troubled transition from colonial viceroyalty to postcolonial republic from the local perspective of Andean peasant politics. Thurner’s reading of the Andean peasantry’s engagement and disengagement with the postcolonial state challenges long-standing interpretations of Peruvian and modern Latin American history and casts a critical eye toward Creole and Eurocentric ideas about citizenship and nationalism.
Working within an innovative and panoramic historical and linguistic framework, Thurner examines the paradoxes of a resurgent Andean peasant republicanism during the mid-1800s and provides a critical revision of the meaning of republican Peru’s bloodiest peasant insurgency, the Atusparia Uprising of 1885. Displacing ahistorical and nationalist readings of Inka or Andean continuity, and undermining the long-held notion that the colonial legacy is the dominant historical force shaping contemporary Andean reality, Thurner suggests that in Peru, the postcolonial legacy of Latin America’s nation-founding nineteenth century transfigured, and ultimately reinvented, the colonial legacy in its own image.
TL;DR: A scenario is proposed that explains the marine iguanas' low genetic divergence, notwithstanding their long evolutionary history in the Galápagos archipelago.
Abstract: Marine iguanas may have inhabited the Galapagos archipelago and its former, now sunken islands for more than 10 million years (Myr). It is therefore surprising that morphological and immunological data indicate little evolutionary divergence within the genus. We utilized mitochondrial DNA (mtDNA) sequence analyses and nuclear DNA fingerprinting to re-evaluate the level and pattern of genetic differentiation among 22 marine iguana populations from throughout the archipelago. Both genetic marker systems detect a low level of within-genus divergence, but they show contrasting levels of geographical subdivision among the populations. The mitochondrial gene pools of populations from different regions of the archipelago are isolated, and the mtDNA pattern appears to follow the sequence in which the islands were colonized by marine iguanas. Conversely, the nuclear DNA study indicates substantial interpopulational gene exchange, and the geographical distribution of the nuclear markers seems to be determined by isolation by distance among the populations. The natural history of marine iguanas suggests that the contrasting nuclear and mitochondrial DNA patterns result from an asymmetric migration behaviour of the two sexes, with higher (active and passive) interisland dispersal for males than females. Separate genetic analyses for the sexes appear to support this hypophesis. Based on these findings, a scenario is proposed that explains the marine iguanas' low genetic divergence, notwithstanding their long evolutionary history in the Galapagos archipelago.
TL;DR: In this article, it was shown that the stable homotopy theory of simplicial B-algebras is equivalent to the stable theory of augmented commutative simplicial ring B. In terms of this equivalence, we can identify Andre-Quillen homology as a stabilization process.
29 Jun 1997
TL;DR: This work considers an information transmission scheme where a stream of messages is encoded using a variable length code, and the code sequence is transmitted over a noisy discrete memoryless channel, and proposes a convolutional-type decoding algorithm assuming that the total length of the transmitted code sequences is known to the decoder.
Abstract: We consider an information transmission scheme where a stream of messages is encoded using a variable length code, and the code sequence, obtained as a concatenation of codewords, is transmitted over a noisy discrete memoryless channel. The decoder constructs a stream of estimates of the messages. Note that the problems that concern the use of variable length codes for transmission over noisy channels also appear if the code is used only for source encoding since any channel coding scheme cannot reduce the level of noise up to zero. We propose a convolutional-type decoding algorithm assuming that: (1) the total length of the transmitted code sequence is known to the decoder and (2) decoding delay is allowed and the decoder constructs a maximum likelihood estimate of the whole stream of messages.
TL;DR: In this article, a topology on the spectrum of a locally coherent Grothendieck category is introduced, where closed subsets are related to certain localizing subcategories which are characterized in terms of Serre sub-categories of the full subcategory of finitely presented objects.
TL;DR: In this paper, the effects of W and Z bosons in the fermion-loop scheme and its application to the six-fermion (LEP2) processes were described.
TL;DR: In this paper, a new measurement of the virtual photon proton asymmetry A1p from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0.0008 1 GeV2 was presented.
20 Apr 1997
TL;DR: This work designed and developed a data acquisition and transportation system that fulfils the needs of real-time control and pattern recognition with tactile sensors and reports on first experimental results with a fingertip prototype performing rolling and sliding movements over a flat surface.
Abstract: Tactile sensor systems are an essential prerequisite for the implementation of complex manipulation and exploration tasks using robots. The desire to perform real-time control and pattern recognition with tactile sensors led us to the design of a cost-effective artificial fingertip. At our laboratory two distinct types of sensors are in use: force/position sensors and slippage detectors. We report on first experimental results with a fingertip prototype performing rolling and sliding movements over a flat surface. To facilitate experimentation with tactile sensors, we designed and developed a data acquisition and transportation system that fulfils our demands on bandwidth, flexibility, and cost. This system consists of two hardware components, a configurable multichannel analog signal sampler to acquire sensor data, and an intelligent dual-ported random-access buffer to avoid data transportation bottlenecks.
TL;DR: Overall energy demand on the mothers is not much lower than in altricial rodents, but lower peak energy demand during lactation in guinea pigs may reduce the coupling of reproduction to periods of high food abundance.
Abstract: Caviomorphs stand out from other small rodents by producing extremely precocial young. Pups begin to nibble solid food right after birth and can survive weaning when 5 d old. We tested whether these properties of young lead to a low cost of lactation in guinea pigs (Cavia porcellus). In contrast to altricial rodents, energy acquisition and expenditure of guinea pig mothers (litter size, three) was highest during the first half of the 23‐d lactation period. Daily metabolizable energy intake at peak lactation was increased by 126% above nonreproducing level and was 65% of the predicted maximal intake. Peak daily energy expenditure was 1.9 times basal metabolic rate, and resting energy expenditure was elevated 26% above nonrepro‐ductive level. From the third day, young consumed solid food and intake increased linearly over the course of lactation. During lactation, total intake of litters through solid food consumption (assuming efficient digestion) amounted to 86% of the energy intake that mothers ...
TL;DR: A perspective, an ideal system of requirements to critically evaluate existing software and to produce future software more adequate both for learning and doing statistics in introductory courses is developed.
Abstract: Summary The community of statisticians and statistics educators should take responsibility for the evaluation and improvement of software quality from the perspective of education. The paper will develop a perspective, an ideal system of requirements to critically evaluate existing software and to produce future software more adequate both for learning and doing statistics in introductory courses. Different kinds of tools and microworlds are needed. After discussing general requirements for such programs, a prototypical ideal software system will be presented in detail. It will be illustrated how such a system could be used to construct learning environments and to support elementary data analysis with exploratory working style.
TL;DR: The component proteins of the iron-only nitrogenase were isolated from Rhodobacter capsulatus and purified in a one-day procedure that included only one column-chromatography step (DEAE-Sephacel), revealing that Rc1Fe and Rc2Mo are immunologically not related.
Abstract: The component proteins of the iron-only nitrogenase were isolated from Rhodobacter capsulatus (delta nifHDK, delta modABCD strain) and purified in a one-day procedure that included only one column-chromatography step (DEAE-Sephacel). This procedure yielded component 1 (FeFe protein, Rc1Fe), which was more than 95% pure, and an approximately 80% pure component 2 (Fe protein, Rc2Fe). The highest specific activities, which were achieved at an Rc2Fe/Rc1Fe molar ratio of 40:1, were 260 (C2H4 from C2H2), 350 (NH3 formation), and 2400 (H2 evolution) nmol product formed x min(-1) x mg protein(-1). The purified FeFe protein contained 26 +/- 4 Fe atoms; it did not contain Mo, V, or any other heterometal atom. The most significant catalytic property of the iron-only nitrogenase is its high H2-producing activity, which is much less inhibited by competitive substrates than the activity of the conventional molybdenum nitrogenase. Under optimal conditions for N2 reduction, the activity ratios (mol N2 reduced/mol H2 produced) obtained were 1:1 (molybdenum nitrogenase) and 1:7.5 (iron nitrogenase). The Rc1Fe protein has only a very low affinity for C2H2. The Km value determined (12.5 kPa), was about ninefold higher than the Km for Rc1Mo (1.4 kPa). The proportion of ethane produced from acetylene (catalyzed by the iron nitrogenase), was strictly pH dependent. It corresponded to 5.5% of the amount of ethylene at pH 6.5 and was almost zero at pH values greater than 8.5. In complementation experiments, component 1 proteins coupled very poorly with the 'wrong' component 2. Rc1Fe, if complemented with Rc2Mo, showed only 10-15% of the maximally possible activity. Cross-reaction experiments with isolated polyclonal antibodies revealed that Rc1Fe and Rc1Mo are immunologically not related. The most active Rc1Fe samples appeared to be EPR-silent in the Na2S2O4-reduced state. However, on partial oxidation with K3[Fe(CN)6] or thionine several signals occurred. The most significant signal appears to be the one at g = 2.27 and 2.06 which deviates from all signals so far described for P clusters. It is a transient signal that appears and disappears reversibly in a redox potential region between -100 mV and +150 mV. Another novel EPR signal (g = 1.96, 1.92, 1.77) occurred on further reduction of Rc1Fe by using turnover conditions in the presence of a substrate (N2, C2H2, H+).
TL;DR: The cytoplasmic protein TraM is one of four essential gene products of the F factor which are involved in DNA transfer after mating pair formation and shows affinity to TraD, a 35-kDa host membrane protein of yet unknown function which may be involved in this anchoring process.
Abstract: The cytoplasmic protein TraM is one of four essential gene products of the F factor which are involved in DNA transfer after mating pair formation. TraM binds to three specific sites within the oriT region. Besides regulation of its own synthesis, the precise function of TraM during conjugation is not yet known. In the present work, the affinity of TraM to TraD was studied in vitro by an overlay assay and by affinity chromatography. Whether the interaction between TraM and TraD causes a transient or permanent anchoring of the F factor to the site of transfer is discussed. A 35-kDa host membrane protein of yet unknown function also shows affinity to TraM and may be involved in this anchoring process as well.
TL;DR: The deletion of this repetitive sequence reduced virulence significantly but did not lead to a complete loss of the virulence phenotype.
Abstract: The tomato pathogen Clavibacter michiganensis subsp. michiganensis NCPPB382, causing bacterial wilt and canker, harbors two plasmids, pCM1 (27.5 kb) and pCM2 (72 kb), carrying genes involved in virulence. The region of plasmid pCM2 encoding the pathogenicity locus pat-1 was mapped by deletion analysis and complementation studies to a 1.5-kb BglII/SmaI DNA fragment. Introduction of the pat-1 region into endophytic, plasmid-free isolates of C. michiganensis subsp. michiganensis converted these bacteria into virulent pathogens. Based on the nucleotide sequence of the pat-1 region, an open reading frame (ORF1) can be predicted, coding for a protein of 280 amino acids and 29.7 kDa with homology to serine proteases. Introduction of a frame-shift mutation in ORF1 leads to a loss of the pathogenic phenotype. Northern (RNA) hybridizations identified an 1.5-knt transcript of the pat-1 structural gene. The site of transcription initiation was mapped by primer extension and a typical -10/-35 region was located with s...
TL;DR: Right hemisphere superiority for recognition of emotions conveyed by facial and prosodic information, a right hemisphere dominance for the recognition of fear and no significant enhancement of right hemisphere superiority under multimodal presentation of emotional stimuli are suggested.