2,125 research outputs found
Gamma-Ray Bursts in the Swift Era
With its rapid-response capability and multiwavelength complement of
instruments, the Swift satellite has transformed our physical understanding of
gamma-ray bursts (GRBs). Providing high-quality observations of hundreds of
bursts, and facilitating a wide range of follow-up observations within seconds
of each event, Swift has revealed an unforeseen richness in observed burst
properties, shed light on the nature of short-duration bursts, and helped
realize the promise of GRBs as probes of the processes and environments of star
formation out to the earliest cosmic epochs. These advances have opened new
perspectives on the nature and properties of burst central engines,
interactions with the burst environment from microparsec to gigaparsec scales,
and the possibilities for non-photonic signatures. Our understanding of these
extreme cosmic sources has thus advanced substantially; yet more than 40 years
after their discovery, GRBs continue to present major challenges on both
observational and theoretical fronts.Comment: 67 pages, 16 figures; ARAA, 2009;
http://arjournals.annualreviews.org/toc/astro/47/
Pneumococcal carriage in vaccine-eligible children and unvaccinated infants in Lao PDR two years following the introduction of the 13-valent pneumococcal conjugate vaccine.
Pneumococcal carriage is a prerequisite for disease, and underpins herd protection provided by pneumococcal conjugate vaccines (PCVs). There are few data on the impact of PCVs in lower income settings, particularly in Asia. In 2013, the Lao People's Democratic Republic (Lao PDR) introduced 13-valent PCV (PCV13) as a 3âŻ+âŻ0 schedule (doses at 6, 10 and 14âŻweeks of age) with limited catch-up vaccination. We conducted two cross-sectional carriage surveys (pre- and two years post-PCV) to assess the impact of PCV13 on nasopharyngeal pneumococcal carriage in 5-8âŻweek old infants (nâŻ=âŻ1000) and 12-23âŻmonth old children (nâŻ=âŻ1010). Pneumococci were detected by quantitative real-time PCR, and molecular serotyping was performed using DNA microarray. Post PCV13, there was a 23% relative reduction in PCV13-type carriage in children aged 12-23âŻmonths (adjusted prevalence ratio [aPR] 0.77 [0.61-0.96]), and no significant change in non-PCV13 serotype carriage (aPR 1.11 [0.89-1.38]). In infants too young to be vaccinated, there was no significant change in carriage of PCV13 serotypes (aPR 0.74 [0.43-1.27]) or non-PCV13 serotypes (aPR 1.29 [0.85-1.96]), although trends were suggestive of indirect effects. Over 70% of pneumococcal-positive samples contained at least one antimicrobial resistance gene, which were more common in PCV13 serotypes (pâŻ<âŻ0.001). In 12-23âŻmonth old children, pneumococcal density of both PCV13 serotypes and non-PCV13 serotypes was higher in PCV13-vaccinated compared with undervaccinated children (pâŻ=âŻ0.004 and pâŻ<âŻ0.001, respectively). This study provides evidence of PCV13 impact on carriage in a population without prior PCV7 utilisation, and provides important data from a lower-middle income setting in Asia. The reductions in PCV13 serotype carriage in vaccine-eligible children are likely to result in reductions in pneumococcal transmission and disease in Lao PDR
Flow of a viscoelastic fluid over a stretching sheet
This paper presents a study of the flow of an incompressible second-order fluid past a stretching sheet. The problem has a bearing on some polymer processing application such as the continuous extrusion of a polymer sheet from a die.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47204/1/397_2005_Article_BF01332078.pd
The ethics of uncertainty for data subjects
Modern health data practices come with many practical uncertainties. In this paper, I argue that data subjectsâ trust in the institutions and organizations that control their data, and their ability to know their own moral obligations in relation to their data, are undermined by significant uncertainties regarding the what, how, and who of mass data collection and analysis. I conclude by considering how proposals for managing situations of high uncertainty might be applied to this problem. These emphasize increasing organizational flexibility, knowledge, and capacity, and reducing hazard
Kingdomâs Rights, Kingdomâs Elite: The Case of Prothonotary George PlemiÄ (1690-1713)
Autori u radu analiziraju druĹĄtveno-politiÄke prilike unutar Hrvatskoga Kraljevstva kroz prizmu politiÄke moÄi i utjecaja protonotara Jurja PlemiÄa u razdoblju od 1690. do 1713. godine, odnosno u razdoblju kada je Juraj PlemiÄ obavljao funkciju kraljevinskoga protonotara. IstiÄuÄi ovlasti protonotarske funkcije kao i utjecaj osobe koja je obnaĹĄala ovu funkciju, autori postavljaju tezu da je protonotar Juraj PlemiÄ bio kljuÄna politiÄka osoba unutar hrvatskoga staleĹĄkog svijeta na prijelazu sa 17. na 18. stoljeÄe i uvelike utjecao na neke od najznaÄajnijih staleĹĄkih odluka nastalih unutar institucije Hrvatskoga sabora u navedenom razdoblju.This article analyses the socio-political circumstances within the Kingdom of Croatia between 1690 and 1713, focusing on Prothonotary Juraj PlemiÄ and his political influence as a case study, to illustrate the main thesis that the kingdomâs rights enabled notaries, nobility judges, vicecomites, treasurers, prothonotaries and vice-bans to create a strong political system and to have a monopoly over decision-making in the Croatian Diet, the Sabor, in the aforementioned period. The prothonotaryâs political potential and power are explained by the authorities and privileges of prothonotary function as well as the ânetworkingâ of parliamentary officials, all of whom belonged to the middle and lower nobility. Consequently, this estate became the privileged negotiation partners within the Kingdom of Croatia for the royal court circles, whereas the magnatesâ political activity was severely curtailed. The story of the Samobor copper mine, âthe 1708 incidentâ and the cooperation between the prothonotary and the bishop of Zagreb in legitimising the succession of Habsburg female line all best illustrate the aforementioned influences and ânetworkingâ of parliamentary officials, and prove that Prothonotary PlemiÄ was the key political figure of the Croatian estates at the turn of the seventeenth and the eighteenth century. The article emphasises the need for further research into the parliamentary functions and the persons who performed these offices, in order to create new interpretations of early modern Croatian history
Bioprospecting Finds the Toughest Biological Material: Extraordinary Silk from a Giant Riverine Orb Spider
Background
Combining high strength and elasticity, spider silks are exceptionally tough, i.e., able to absorb massive kinetic energy before breaking. Spider silk is therefore a model polymer for development of high performance biomimetic fibers. There are over 41.000 described species of spiders, most spinning multiple types of silk. Thus we have available some 200.000+ unique silks that may cover an amazing breadth of material properties. To date, however, silks from only a few tens of species have been characterized, most chosen haphazardly as model organisms (Nephila) or simply from researchers' backyards. Are we limited to âblindly fishingâ in efforts to discover extraordinary silks? Or, could scientists use ecology to predict which species are likely to spin silks exhibiting exceptional performance properties?
Methodology
We examined the biomechanical properties of silk produced by the remarkable Malagasy âDarwin's bark spiderâ (Caerostris darwini), which we predicted would produce exceptional silk based upon its amazing web. The spider constructs its giant orb web (up to 2.8 m2) suspended above streams, rivers, and lakes. It attaches the web to substrates on each riverbank by anchor threads as long as 25 meters. Dragline silk from both Caerostris webs and forcibly pulled silk, exhibits an extraordinary combination of high tensile strength and elasticity previously unknown for spider silk. The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3. Thus, C. darwini silk is more than twice tougher than any previously described silk, and over 10 times better than KevlarÂŽ. Caerostris capture spiral silk is similarly exceptionally tough.
Conclusions
Caerostris darwini produces the toughest known biomaterial. We hypothesize that this extraordinary toughness coevolved with the unusual ecology and web architecture of these spiders, decreasing the likelihood of bridgelines breaking and collapsing the web into the river. This hypothesis predicts that rapid change in material properties of silk co-occurred with ecological shifts within the genus, and can thus be tested by combining material science, behavioral observations, and phylogenetics. Our findings highlight the potential benefits of natural historyâinformed bioprospecting to discover silks, as well as other materials, with novel and exceptional properties to serve as models in biomimicry.Primary funding for this work came from the Slovenian Research Agency (grant Z1-9799-0618-07 to I. Agnarsson), the National Geographic Society (grant 8655-09 to the authors), and the National Science Foundation (grants DBI-0521261, DEB-0516038 and IOS-0745379 to T. Blackledge). Additional funding came from the European Community 6th Framework Programme (a Marie Curie International Reintegration Grant MIRG-CT-2005 036536 to M. Kuntner). The 2001 field work was supported by the Sallee Charitable Trust grant to I. Agnarsson and M. Kuntner and by a United States National Science Foundation grant (DEB-9712353) to G. Hormiga and J. A. Coddington. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe
Emergent complex neural dynamics
A large repertoire of spatiotemporal activity patterns in the brain is the
basis for adaptive behaviour. Understanding the mechanism by which the brain's
hundred billion neurons and hundred trillion synapses manage to produce such a
range of cortical configurations in a flexible manner remains a fundamental
problem in neuroscience. One plausible solution is the involvement of universal
mechanisms of emergent complex phenomena evident in dynamical systems poised
near a critical point of a second-order phase transition. We review recent
theoretical and empirical results supporting the notion that the brain is
naturally poised near criticality, as well as its implications for better
understanding of the brain
Eph/Ephrin Profiling in Human Breast Cancer Reveals Significant Associations between Expression Level and Clinical Outcome
Pre-clinical studies provide compelling evidence that Eph family receptor tyrosine kinases (RTKs) and ligands promote cancer growth, neovascularization, invasion, and metastasis. Tumor suppressive roles have also been reported for the receptors, however, creating a potential barrier for clinical application. Determining how these observations relate to clinical outcome is a crucial step for translating the biological and mechanistic data into new molecularly targeted therapies. We investigated eph and ephrin expression in human breast cancer relative to endpoints of overall and/or recurrence-free survival in large microarray datasets. We also investigated protein expression in commercial human breast tissue microarrays (TMA) and Stage I prognostic TMAs linked to recurrence outcome data. We found significant correlations between ephA2, ephA4, ephA7, ephB4, and ephB6 and overall and/or recurrence-free survival in large microarray datasets. Protein expression in TMAs supported these trends. While observed no correlation between ephrin ligand expression and clinical outcome in microarray datasets, ephrin-A1 and EphA2 protein co-expression was significantly associated with recurrence in Stage I prognostic breast cancer TMAs. Our data suggest that several Eph family members are clinically relevant and tractable targets for intervention in human breast cancer. Moreover, profiling Eph receptor expression patterns in the context of relevant ligands and in the context of stage may be valuable in terms of diagnostics and treatment
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