87 research outputs found
Violator Spaces: Structure and Algorithms
Sharir and Welzl introduced an abstract framework for optimization problems,
called LP-type problems or also generalized linear programming problems, which
proved useful in algorithm design. We define a new, and as we believe, simpler
and more natural framework: violator spaces, which constitute a proper
generalization of LP-type problems. We show that Clarkson's randomized
algorithms for low-dimensional linear programming work in the context of
violator spaces. For example, in this way we obtain the fastest known algorithm
for the P-matrix generalized linear complementarity problem with a constant
number of blocks. We also give two new characterizations of LP-type problems:
they are equivalent to acyclic violator spaces, as well as to concrete LP-type
problems (informally, the constraints in a concrete LP-type problem are subsets
of a linearly ordered ground set, and the value of a set of constraints is the
minimum of its intersection).Comment: 28 pages, 5 figures, extended abstract was presented at ESA 2006;
author spelling fixe
Activation of chimeric and full-length growth hormone receptors by growth hormone receptor monoclonal antibodies: A specific conformational change may be required for full-length receptor signaling
Signal transduction by the growth hormone receptor (GHR) occurs through growth hormone (GH)-induced dimerization of two GHRs to form a trimeric complex, It is thought that dimerization alone is sufficient for signaling, since monoclonal antibodies (mAbs) against the extracellular domain of the GHR elicit proliferation of FDC-P1 cells transfected with a chimeric receptor comprising the extracellular domain of the GHR and the fibronectin and cytoplasmic domains of the murine granulocyte colony-stimulating factor receptor, We have screened 14 GHR mAbs for proliferative activity against characterized FDC-P1 and BaF-B03 cell lines stably expressing the full-length human, rabbit, or rat GHR, or the chimeric human GHR/granulocyte colony-stimulating factor receptor, and for transactivation of the c-fos promoter and STAT activation. With the chimeric receptor, eight mAbs were able to elicit proliferation, although there was no correlation between inhibition of hormone binding and agonist activity. In contrast, no mAbs were able to act as agonists with the full-length GHR FDC-P1 cell lines, although nine competed with GH for binding, A weak proliferative response was observed in the BaF-B03 cell lines with two of the mAbs (263 and 1C9), and the addition of anti-mouse F(ab)(2) resulted in increased signaling in the hGHR BaF-B03 cell line to a plateau of 28 +/- 4% of the GH maximum for mAb 263. These data could indicate considerable stringency in the ability of mAbs to correctly dimerize the full-length GI-IR. However, the ability of mAb 263 to stimulate a mutant hGHR altered in the F'-G' loop of domain 2 was nearly abolished, concurrent with an increased affinity of this mAb for the receptor. Since the F'-G' loop undergoes a conformational change on GH binding and is necessary for full proliferative signaling, we propose that in addition to promoting receptor dimerization, mAb 263 may induce specific changes in receptor conformation similar to GH, which are required for the biological response
Beta diversity of urban floras among European and non-European cities.
Aim Cities represent an ideal study system for assessing how intensive land-use change and biotic interchange have altered beta diversity at broad geographic extents. Here we test the hypothesis that floras in cities located in disparate regions of the globe are being homogenized by species classified as invasive (naturalized species that have spread over a large area) or as a European archaeophyte (species introduced into Europe before ad 1500 from the Mediterranean Basin).We also test the prediction that the global influences of European activities (colonization, agriculture, commerce) have supported this outcome.
Location One hundred and ten cities world-wide.
Methods We examined the richness and composition of urban floras among European (n = 85) and non-European cities (n = 25) for species classified as native or non-native, or further classified as European archaeophyte or invasive. We modelled how geographic, climatic and anthropogenic factors were related to compositional
similarity between European and non-European cities.
Results We found that most plants in the cities we examined, particularly non-
European cities, were native and unique to each city. Non-native species were similarly unique, but occurred in much lower proportions relative to natives. Although European archaeophytes and invasive species also occurred in lower proportions, they had similar compositions among cities. European archaeophytes were most prevalent in European cities, but were most similar among non-European cities. Contrasting European and non-European cities, geography and
climate were most relevant for native and invasive species, whereas climate and
agriculture were most relevant for European archaeophytes.
Main conclusions Cities in disparate regions of the globe retain regionally distinct native and non-native plant assemblages, while invasive species, and especially
European archaeophytes, were associated with lower beta diversity among cities. These findings suggest that intensive land-use change and biotic interchange, shaped through European influences, have had a world-wide effect on the beta diversity of urban plant assemblages
Relations between Financing and Output in the Not-for-Profit Hospital
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68639/2/10.1177_107755878804500204.pd
The Physics of Star Cluster Formation and Evolution
© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe
Catching Element Formation In The Act ; The Case for a New MeV Gamma-Ray Mission: Radionuclide Astronomy in the 2020s
High Energy Astrophysic
Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures
Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo
- …