169,856 research outputs found
Belief propagation for weighted b-matchings on arbitrary graphs and its relation to linear programs with integer solutions
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Borgs are giant genetic elements with potential to expand metabolic capacity
No full textAnaerobic methane oxidation exerts a key control on greenhouse gas emissions(1), yet factors that modulate the activity of microorganisms performing this function remain poorly understood. Here we discovered extraordinarily large, diverse DNA sequences that primarily encode hypothetical proteins through studying groundwater, sediments and wetland soil where methane production and oxidation occur. Four curated, complete genomes are linear, up to approximately 1 Mb in length and share genome organization, including replichore structure, long inverted terminal repeats and genome-wide unique perfect tandem direct repeats that are intergenic or generate amino acid repeats. We infer that these are highly divergent archaeal extrachromosomal elements with a distinct evolutionary origin. Gene sequence similarity, phylogeny and local divergence of sequence composition indicate that many of their genes were assimilated from methane-oxidizing Methanoperedens archaea. We refer to these elements as ‘Borgs’. We identified at least 19 different Borg types coexisting with Methanoperedens spp. in four distinct ecosystems. Borgs provide methane-oxidizing Methanoperedens archaea access to genes encoding proteins involved in redox reactions and energy conservation (for example, clusters of multihaem cytochromes and methyl coenzyme M reductase). These data suggest that Borgs might have previously unrecognized roles in the metabolism of this group of archaea, which are known to modulate greenhouse gas emissions, but further studies are now needed to establish their functional relevance
The crossover from first to second-order finite-size scaling: a numerical study
No full textWe consider a particular case of the two dimensional Blume-Emery-Griffiths
model to study the finite-size scaling for a field driven first-order phase
transition with two coexisting phases not related by a symmetry. For low
temperatures we verify the asymptotic (large volume) predictions of the
rigorous theory of Borgs and Kotecky. Near the critical temperature we
show that all data fit onto a unique curve, even when the correlation
length becomes comparable to or larger than the size of the system,
provided the linear dimension of the system is rescaled by
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
Slöjd ur ett politiskt perspektiv – En granskning av slöjdens kursplaner
No full textMed anledning av de nya styrdokumenten för grundskolan, Lgr11, som kommer att träda i kraft höstterminen 011 har
vi gjort en studie av kursplanerna för ämnet slöjd. Utgångspunkten är Kajsa Borgs bok ”Slöjdämnet i förändring”, vilket
är en redogörelse för slöjdens kursplaner 196–1994. Denna studie tar vid där Borgs bok slutar och behandlar de två
senare kursplanerna kpl000 och Lgr11. Genom studier av olika läroplansteorier har det tydliggjorts vilka delar av
dessa styrdokument som är relevanta att studera i dagsläget. Vi har med hjälp av de textanalytiska metoderna
innehållsanalys och dimensioner som analysverktyg studerat dessa kursplaner för att se likheter och skillnader dem
emellan. Vi har särskilt fokuserat på hur ansvar, utveckling och direktiv skrivs fram i dessa texter. Genom Borgs studier
kan även mönster ur ett långtidsperspektiv urskiljas. Då kursplaner, och således vårt uppdrag som lärare, är politiskt
styrda är det relevant att se åt vilket håll regerande politiker styr slöjden. I kpl000 är elevens utveckling och
delaktighet i ämnet framskriven. I Lgr11 skrivs samhällets utveckling fram. Elevens delaktighet skrivs inte fram utan
istället är det skolans ansvar att ge eleven förutsättningar för att uppnå ställda mål. Vår undersökning visar även att
Lgr11 är mycket tydligare i fråga om material och teknikbenämningar, vilket skall göra den enklare att tolka på ett
korrekt sätt för att få en likvärdig skola
Percolation on dense graph sequences
No full textIn this paper we determine the percolation threshold for an arbitrary sequence of dense graphs . Let be the largest eigenvalue of the adjacency matrix of , and let be the random subgraph of obtained by keeping each edge independently with probability . We show that the appearance of a giant component in has a sharp threshold at . In fact, we prove much more: if converges to an irreducible limit, then the density of the largest component of tends to the survival probability of a multi-type branching process defined in terms of this limit. Here the notions of convergence and limit are those of Borgs, Chayes, Lov\'asz, S\'os and Vesztergombi. In addition to using basic properties of convergence, we make heavy use of the methods of Bollob\'as, Janson and Riordan, who used multi-type branching processes to study the emergence of a giant component in a very broad family of sparse inhomogeneous random graphs
Limits of randomly grown graph sequences
No full textAbstractMotivated in part by various sequences of graphs growing under random rules (such as Internet models), Borgs, Chayes, Lovász, Sós, Szegedy and Vesztergombi introduced convergent sequences of dense graphs and their limits. In this paper we use this framework to study one of the motivating classes of examples, namely randomly growing graphs. We prove the (almost sure) convergence of several such randomly growing graph sequences, and determine their limit. The analysis is not always straightforward: in some cases the cut-distance from a limit object can be directly estimated, while in other cases densities of subgraphs can be shown to converge
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
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
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