Distribution Functions of the Nucleon and Pion in the Valence Region

We provide an experimental and theoretical perspective on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain; namely, Bjorken-x \gtrsim 0.4. This domain is key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. We focus on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the Standard Model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, we explain that an upgraded Jefferson Lab facility is well-suited to provide new data on the nucleon, while a future electron ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, J-PARC and GSI, to push into the large-x domain for both mesons and nucleons. We argue furthermore that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum field theory; and a fuller exploitation of those methods.Comment: Review article: 133 double-spaced pages, 44 figures, 6 table

Sturcture of the Goldstone Bosons

The feasibility of measuring the pion and kaon structure functions has been investigated. A high luminosity electron-proton collider would make these measurements feasible. Also, it appears feasible to measure these structure functions in a nuclear medium. Simulations using the RAPGAP Monte Carlo of a possible pion structure function measurement are presented.Comment: To appear in the proceedings of the Second Workshop on Physics with an Electron Polarized Light-Ion Collider, 14-16 Sept 2000, Cambridge, Ma 6 pages, 5 figures, late

Nucleon spin structure at very high-x

Dyson-Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence of dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x =1. A comparison with predictions from other approaches plus a consideration of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x =1 can add considerably to our capacity for discriminating between contemporary pictures of nucleon structure.Comment: 6 pages, 1 table, 3 figures. To appear in Phys. Lett.

Dominant Nuclear Outflow Driving Mechanisms in Powerful Radio Galaxies

In order to identify the dominant nuclear outflow mechanisms in Active Galactic Nuclei, we have undertaken deep, high resolution observations of two compact radio sources (PKS 1549-79 and PKS 1345+12) with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope. Not only are these targets known to have powerful emission line outflows, but they also contain all the potential drivers for the outflows: relativistic jets, quasar nuclei and starbursts. ACS allows the compact nature (<0.15") of these radio sources to be optically resolved for the first time. Through comparison with existing radio maps we have seen consistency in the nuclear position angles of both the optical emission line and radio data. There is no evidence for bi-conical emission line features on the large-scale and there is a divergance in the relative position angles of the optical and radio structure. This enables us to exclude starburst driven outflows. However, we are unable to clearly distinguish between radiative AGN wind driven outflows and outflows powered by relativistic radio jets. The small scale bi-conical features, indicative of such mechanisms could be below the resolution limit of ACS, especially if aligned close to the line of sight. In addition, there may be offsets between the radio and optical nuclei induced by heavy dust obscuration, nebular continuum or scattered light from the AGN.Comment: 9 pages, 8 figures, emulateapj, ApJ Accepte

Dynamics of antimicrobial resistance in intestinal Escherichia coli from children in community settings in South Asia and sub-Saharan Africa.

The dynamics of antimicrobial resistance (AMR) in developing countries are poorly understood, especially in community settings, due to a sparsity of data on AMR prevalence and genetics. We used a combination of phenotyping, genomics and antimicrobial usage data to investigate patterns of AMR amongst atypical enteropathogenic Escherichia coli (aEPEC) strains isolated from children younger than five years old in seven developing countries (four in sub-Saharan Africa and three in South Asia) over a three-year period. We detected high rates of AMR, with 65% of isolates displaying resistance to three or more drug classes. Whole-genome sequencing revealed a diversity of known genetic mechanisms for AMR that accounted for >95% of phenotypic resistance, with comparable rates amongst aEPEC strains associated with diarrhoea or asymptomatic carriage. Genetic determinants of AMR were associated with the geographic location of isolates, not E. coli lineage, and AMR genes were frequently co-located, potentially enabling the acquisition of multi-drug resistance in a single step. Comparison of AMR with antimicrobial usage data showed that the prevalence of resistance to fluoroquinolones and third-generation cephalosporins was correlated with usage, which was higher in South Asia than in Africa. This study provides much-needed insights into the frequency and mechanisms of AMR in intestinal E. coli in children living in community settings in developing countries

Assessment of the Quality of Elective Abdominal Aortic Aneurysm Repair Patient Information on the Internet Using the Modified Ensuring Quality Information for Patients Tool.

OBJECTIVE: This study aimed to assess the quality of patient information material regarding elective abdominal aortic aneurysm (AAA) repair on the internet using the Modified Ensuring Quality Information for Patients (MEQIP) tool. METHODS: A qualitative assessment of internet based patient information was performed. The 12 most used search terms relating to AAA repair were identified using Google Trends, with the first 10 pages of websites retrieved for each term searched. Duplicates were removed, and information for patients undergoing elective AAA were selected. Further exclusion criteria were marketing material, academic journals, videos, and non-English language sites. The remaining websites were then MEQIP scored independently by two reviewers, producing a final score by consensus. RESULTS: A total of 1 297 websites were identified, with 235 (18.1%) eligible for analysis. The median MEQIP score was 18 (interquartile range [IQR] 14, 21) out of a possible 36. The highest score was 33. The 99th percentile MEQIP scoring websites scored > 27, with four of these six sites representing online copies of hospital patient information leaflets, however hospital sites overall had lower median MEQIP scores than most other institution types. MEQIP subdomain median scores were: content, 8 (IQR 6, 11); identification, 3 (IQR 1, 3); and structure, 7 (IQR 6, 9). Of the analysed websites, 77.9% originated from the USA (median score 17) and 12.8% originated in the UK (median score 22). Search engine ranking was related to website institution type but had no correlation with MEQIP. CONCLUSION: When assessed by the MEQIP tool, most websites regarding elective AAA repair are of questionable quality. This is in keeping with studies in other surgical and medical fields. Search engine ranking is not a reliable measure of quality of patient information material regarding elective AAA repair. Health practitioners should be aware of this issue as well as the whereabouts of high quality material to which patients can be directed

Evolution of structural and optical properties of ion-beam synthesized GaAsN nanostructures

We have investigated the evolution of structural and optical properties of GaAsN nanostructures synthesized by N ion implantation into epitaxial GaAs, followed by rapid thermal annealing. Transmission electron microscopy and x-ray diffraction indicate the formation of nanometer-sized crystallites with lattice parameters close to those of pure zincblende GaN. The average crystallite size increases with annealing temperature while the size distribution is self-similar and the volume fraction remains constant, suggesting a coarsening process governed by Ostwald ripening. These GaAsN nanostructures exhibit significant photoluminescence in the near infrared range. The apparent lowering of the fundamental band gap is likely due to the incorporation of a small amount of As in GaN. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70225/2/JAPIAU-92-7-4012-1.pd

Long Term Outcomes and Durability of Fenestrated Endovascular Aneurysm Repair: A Meta-analysis of Time to Event Data

Objective Despite widespread use, long term outcomes for fenestrated endovascular aneurysm repair (FEVAR) are uncertain. This meta-analysis reports long term survival, freedom from re-intervention, target vessel patency, and one year sac regression after FEVAR. Data Sources Systematic review and meta-analysis to pool time to event data according to PRISMA guidelines. The study was registered with the international prospective register of systematic reviews (PROSPERO) (ID: CRD42023401468). Review Methods Medline, Embase, and Cochrane databases were searched 1992 – 2023; articles were independently screened by two authors. Publication of complete time to event data for any outcome of interest was an inclusion criterion. Raw Kaplan–Meier probabilities were directly extracted from published curves and pooled by random effects. Risk of bias was assessed using ROBINSI and certainty with GRADE. Results A total of 3 569 records were retrieved, 2 869 screened after duplicate removal, yielding 37 included studies (n = 4 371). Pooled mean age was 73.2 years (interquartile range [IQR] 72.2, 73.7) and 87.4% male (95% confidence interval [CI] 85.8 – 88.9). Pooled Kaplan–Meier estimated probabilities of survival (n = 34 studies, n = 4 192 patients) at one, three, and five years were 91.6% (95% CI 90.2 – 92.9), 80.8% (95% CI 78.0 – 83.2), and 65.1% (95% CI 60.9 – 69.1). For freedom from re-intervention (n = 24, n = 3 211 patients) at one, three, and five years these were 90.2% (95% CI 87.3 – 92.7), 80.9% (95% CI 76.5 – 84.9), and 73.8% (95% CI 67.1 – 79.6). For target vessel patency (n = 13, n = 5805 target vessels) at one, three, and five years, these were 96.6% (95% CI 94.9 – 98.0), 94.5% (95% CI 91.7 – 96.7), and 93.1% (95% CI 89.3 – 96.0). Pooled estimate of sac regression (n = 8, n = 560) at one year was 40.2% (95% CI 28.9 – 52.7). Risk of bias was judged as moderate in 11 studies and low for the remaining 26. Conclusion There are moderate to low certainty data supporting reasonable long term outcome estimates following fenestrated endovascular aneurysm repair. Beyond five years there is a lack of data in the literature