131,116 research outputs found
Statistical equilibrium of tetrahedra from maximum entropy principle
No full textDiscrete formulations of (quantum) gravity in four spacetime dimensions build space out of tetrahedra. We investigate a statistical mechanical system of tetrahedra from a many-body point of view based on nonlocal, combinatorial gluing constraints that are modeled as multiparticle interactions. We focus on Gibbs equilibrium states, constructed using Jaynes's principle of constrained maximization of entropy, which has been shown recently to play an important role in characterizing equilibrium in background-independent systems. We apply this principle first to classical systems of many tetrahedra using different examples of geometrically motivated constraints. Then for a system of quantum tetrahedra, we show that the quantum statistical partition function of a Gibbs state with respect to some constraint operator can be reinterpreted as a partition function for a quantum field theory of tetrahedra, taking the form of a group field theory
Functional heterogeneity of pulmonary surfactant protein-D in cystic fibrosis
No full textPulmonary surfactant protein-D (SP-D) is a soluble collagenous C-type lectin with important anti-microbial and anti-inflammatory properties. Although it is subject to functionally relevant modification by common polymorphisms and unregulated inflammation, the functional status of SP-D in cystic fibrosis (CF) remains unclear. Given the importance of infection and inflammation in CF lung pathology we have undertaken the first systematic analysis of SP-D lectin activity in this population. By ELISA, we found that airway lavage fluid SP-D expression was greater in CF compared to control patients but was reduced in CF patients with infection and correlated negatively with markers of neutrophilic inflammation. In a functional assay, the percentage of SP-D capable of binding zymosan rarely exceeded 60% in CF or control patients and similarly restricted binding activity was observed towards maltose–agarose. SP-D lectin activity also correlated negatively with infection and neutrophilic inflammation but there was little evidence of major proteolytic degradation amongst the non-bound material. SP-D which failed to bind zymosan exhibited features of lower oligomeric form compared to bound material when tested by native gel electrophoresis. Furthermore, when separated by gel chromatography, high and low oligomeric populations of SP-D were observed in CF lavage fluid but only high oligomeric forms exhibited substantial lectin activity towards yeast derived mannan. Our data demonstrate that oligomeric heterogeneity underlies functional diversity amongst SP-D in health and disease and that dynamic regulation of oligomerisation is an important feature of SP-D biology.<br/
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Increased prevalence of low oligomeric state surfactant protein D with restricted lectin activity in bronchoalveolar lavage fluid from preterm infants
No full textBackground: Surfactant protein D (SP-D) is a soluble oligomeric C-type lectin known to protect against lipopolysaccharide and ventilator-induced lung injury in preterm lambs. Here we assess the expression and functional status of SP-D in bronchoalveolar lavage fluid (BALF) from preterm infants at risk of chronic lung disease (CLD) of prematurity and term controls. This is the first systematic evaluation of SP-D function in any clinical cohort.Methods: SP-D was quantified in BALF from 28 ventilated preterm infants and five ventilated term infants. SP-D lectin activity was tested in a zymosan binding assay followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western blot in BALF from the same infants. SP-D lectin activity was also tested towards maltose-agarose and mannan for selected BALF samples.Results: SP-D expression was lower on day 1 in those preterm infants who subsequently developed CLD but increased over the first 5 days of life in term and preterm neonates. The percentage of neonatal SP-D capable of binding zymosan rarely exceeded 50% in any BALF sample and was 3.5 times lower in preterm infants than term infants on day 1 of life. Similar binding defects were observed towards maltose-agarose and mannan. SDS-PAGE analysis revealed that zymosan-bound SP-D was more highly oligomerised (?12-mers) than unbound SP-D, which was composed primarily of trimers and lower oligomeric forms.Conclusions: Substantial and functionally relevant variation in the expression and oligomeric distribution of SP-D exists between preterm and term neonatal lung secretions. This has implications for proposed SP-D replacement therapy in this population
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
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