1,467 research outputs found
Die zusammenhaltende Region
No full textDirksmeier P, Fücker S, Crückeberg J. Die zusammenhaltende Region. In: Ermann U, Höfner M, Hostniker S, Preininger EM, Simic D, eds. Die Region - eine Begriffserkundung. transcript Verlag; 2022: 303-314
efficiency and evolution of R&D Networks.
No full textThis work introduces a new model to investigate the efficiency and evolution of networks of firms exchanging knowledge in R&D partnerships. We first examine the efficiency of a given network structure from the point of view of maximizing total profits in the industry. We show that the efficient network structure depends on the marginal cost of collaboration. When the marginal cost is low, the complete graph is efficient. However, a high marginal cost implies that the efficient network is sparser and has a core-periphery structure. Next, we examine the evolution of the network structure when the decision on collaborating partners is decentralized. We show the existence of multiple equilibrium structures which are in general inefficient. This is due to (i) the path dependent character of the partner selection process, (ii) the presence of knowledge externalities and (iii) the presence of severance costs involved in link deletion. Finally, we study the properties of the emerging equilibrium networks and we show that they are coherent with the stylized facts on R&D networks.R&D networks;technology spillovers;network efficiency;network formation;
Measurement of the two-jet differential cross section in p(p)over-bar collisions at root s=1800 GeV
No full textA measurement is presented of the two-jet differential cross section d(3)sigma /dE(T)d eta (1)d eta (2) at center of mass energy roots = 1800 GeV in p (p) over bar collisions. The results are based on an integrated luminosity of 86 pb(-1) collected during 1994 to 1995 by the CDF Collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy E-T of a jet in the pseudorapidity region 0.1(1)\<0.7 for four different pseudorapidity bins of a second jet restricted to 0.1<\ eta (2) \<3.0. The results are compared with next-to-leading order QCD calculations determined using the CTEQ4 and MRST sets of parton distribution functions. None of the sets ex.amined in this analysis provides a good description of the data
Eigenvalue bounds for the signless laplacian
No full textWe extend our previous survey of properties of spectra of signless Laplacians of graphs. Some new bounds for eigenvalues are given, and the main result concerns the graphs whose largest eigenvalue is maximal among the graphs with fixed numbers of vertices and edges. The results are presented in the context of a number of computer-generated conjectures
Methodological approach towards a Gap Assessment of the Serbian microbiology system in the function of surveillance in line with EU standards and acquis
No full textIntroduction. Italian and Serbian Health authorities performed an in-depth Gap Assessment of the Serbian microbiology system in the function of communicable disease surveillance using a methodology adapted to context and information needs. Methods. There were two study phases: a capacity based survey and an equipment mapping survey. Invited participants included national health authorities, heads of national reference laboratories and of public/private diagnostic laboratories in Serbia. Findings were analysed preliminarily and identified gaps were discussed, prioritized and validated through two ad hoc workshops involving all concerned institutions. Results. The Gap Assessment was performed between September and December 2017. The overall response rate was 69% for phase one and 74% for phase two. Identified gaps were assessed as highly relevant during the project workshops. Discussion. Gaps and priorities were highlighted, validated, and studied with a suitable level of detail to develop a concrete action-plan. The same methodological approach could be used to monitor progress in Serbia as well as in other EU candidate countries
UNCOVERING THE MECHANISM OF CHROMATIN ASSOCIATION OF THE PAF1 TRANSCRIPTION ELONGATION COMPLEX
No full textPaf1C co-localizes with Pol II and influences gene expression by regulating transcription initiation, elongation and termination. Some crucial functions of Paf1C include promoting co-transcriptional histone modifications and recruiting termination factors. The mechanism of chromatin recruitment of Paf1C was obscure. We identified the importance of a conserved region within the Rtf1 subunit of Paf1C, termed the ORF association region (OAR), in chromatin-tethering of Paf1C. I found that the interaction of Paf1C with the transcription elongation factor Spt5 was mediated by the Rtf1 OAR and the Spt5 C-terminal region (CTR). Binding assays established the direct nature of the Rtf1-Spt5 interaction and the sufficiency of the Rtf1 OAR and the Spt5 CTR for this interaction. ChIP assays demonstrated the ability of the OAR to mimic the chromatin association pattern of Paf1C, independent of Paf1C but dependent on the Spt5 CTR and the Bur1 kinase. This suggests that the targeting of the OAR tethers Paf1C to chromatin. Collectively, these results provide a molecular mechanism for coupling Paf1C with the transcription machinery.
Additionally, I found that substitution of OAR residues predicted to be important for the human Rtf1 OAR-Spt5 CTR interaction in the OAR-CTR co-crystal impaired the chromatin association of Paf1C supporting the relevance of the co-crystal interactions. Furthermore, I showed that strains that are doubly mutated in the OAR and the Cdc73 C-domain exhibited cumulative reduction in Paf1C chromatin occupancy. Consistently, I showed that cells lacking both the OAR and the C-domain lose Paf1C-mediated histone modifications. This indicates that the Rtf1 OAR and the Cdc73 C-domain facilitate dual-attachment of Paf1C to chromatin.
My work has also provided better understanding of the function of the histone modification domain (HMD) of Rtf1. I found that overexpression of the HMD was essential for it to promote histone modifications. Additionally, I showed that the HMD is sufficient for the H2B K123 Ub, the mark upstream of the H3 K4 and H3 K79 methylation events, but the rest of Paf1C is required for the HMD to stimulate H3 K4 Me3 modification. Cumulatively, my findings provide additional insight into the regulation of histone modifications by the Rtf1 HMD
Graphs with least eigenvalue -2: ten years on
No full textThe authors' monographSpectral Generalizations of Line Graphswas published in 2004, following the successful use of star complements to complete the classification of graphs with least eigenvalue −2. Guided by citations of the book, we survey progress in this area over the past decade. Some new observations are included
Star complements and exceptional graphs
No full textLet G be a finite graph of order n with an eigenvalue ? of multiplicity k. (Thus the ?-eigenspace of a (0,1)-adjacency matrix of G has dimension k.) A star complement for ? in G is an induced subgraph G-X of G such that |X|=k and G-X does not have ? as an eigenvalue. An exceptional graph is a connected graph, other than a generalized line graph, whose eigenvalues lie in [-2,?). We establish some properties of star complements, and of eigenvectors, of exceptional graphs with least eigenvalue -2
The northern ROSAT All-Sky (NORAS) galaxy cluster survey. I. X-ray properties of clusters detected as extended X-ray sources
No full textIn the construction of an X-ray-selected sample of galaxy clusters for cosmological studies, we have assembled a sample of 495 X-ray sources found to show extended X-ray emission in the first processing of the ROSAT All-Sky Survey. The sample covers the celestial region with declination delta greater than or equal to 0 degrees and Galactic latitude \b(II)\ greater than or equal to 20 degrees and comprises sources with a count rate greater than or equal to 0.06 counts s(-1) and a source extent likelihood of L greater than or equal to 7. In an optical follow-up identification program we find 378 (76%) of these sources to be clusters of galaxies. It was necessary to reanalyze the sources in this sample with a new X-ray source characterization technique to provide more precise values for the X-ray flux and source extent than obtained from the standard processing. This new method, termed growth curve analysis (GCA), has the advantage over previous methods in its ability to be robust, to be easy to model and to integrate into simulations, to provide diagnostic plots for visual inspection, and to make extensive use of the X-ray data. The source parameters obtained assist the source identification and provide more precise X-ray fluxes. This reanalysis is based on data from the more recent second processing of the ROSAT Survey. We present a catalog of the cluster sources with the X-ray properties obtained as well as a list of the previously flagged extended sources that are found to have a noncluster counterpart. We discuss the process of source identification from the combination of optical and X-ray data. To investigate the overall completeness of the cluster sample as a function of the X-ray flux limit, we extend the search for X-ray cluster sources to the data of the second processing of the ROSAT Survey for the northern sky region between 9(h) and 14(h) in right ascension. We include the search for X-ray emission of known clusters as well as a new investigation of extended X-ray sources. In the course of this search we find X-ray emission from 85 additional Abell clusters and 56 very probable cluster candidates among the newly found extended sources. A comparison of the X-ray cluster number counts of the NORAS sample with the ROSAT-ESO Flux-limited X-Ray (REFLEX) Cluster Survey results leads to an estimate of the completeness of the NORAS sample of ROSAT All-Sky Survey (RASS) I extended clusters of about 50% at an X-ray flux of F(X)(0.1-2.4 keV) = 3 x 10(-12) ergs s(-1) cm(-2). The estimated completeness achieved by adding the supplementary sample in the study area amounts to about 82% in comparison to REFLEX. The low completeness introduces an uncertainty in the use of the sample for cosmological statistical studies that will be cured with the completion of the continuing Northern ROSAT All-Sky (NORAS) Cluster Survey project
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