2,797 research outputs found
The Glue Around Quarks and the Interquark Potential
The quarks of quark models cannot be identified with the quarks of the QCD
Lagrangian. We review the restrictions that gauge field theories place on any
description of physical (colour) charges. A method to construct charged
particles is presented. The solutions are applied to a variety of applications.
Their Green's functions are shown to be free of infra-red divergences to all
orders in perturbation theory. The interquark potential is analysed and it is
shown that the interaction responsible for anti-screening results from the
force between two separately gauge invariant constituent quarks. A fundamental
limit on the applicability of quark models is identified.Comment: 4 pages, LaTeX, talk given at Montpellier meeting QCD9
Relationship between dairy cow genetic merit and profit on commercial spring calving dairy farms
peer-reviewedBecause not all animal factors influencing profitability can be included in total merit breeding indices for profitability, the
association between animal total merit index and true profitability, taking cognisance of all factors associated with costs and
revenues, is generally not known. One method to estimate such associations is at the herd level, associating herd average genetic
merit with herd profitability. The objective of this study was to primarily relate herd average genetic merit for a range of traits,
including the Irish total merit index, with indicators of performance, including profitability, using correlation and multiple
regression analyses. Physical, genetic and financial performance data from 1131 Irish seasonal calving pasture-based dairy farms
were available following edits; data on some herds were available for more than 1 year of the 3-year study period (2007 to 2009).
Herd average economic breeding index (EBI) was associated with reduced herd average phenotypic milk yield but with greater
milk composition, resulting in higher milk prices. Moderate positive correlations (0.26 to 0.61) existed between genetic merit for
an individual trait and average herd performance for that trait (e.g. genetic merit for milk yield and average per cow milk yield).
Following adjustment for year, stocking rate, herd size and quantity of purchased feed in the multiple regression analysis, average
herd EBI was positively and linearly associated with net margin per cow and per litre as well as gross revenue output per cow
and per litre. The change in net margin per cow per unit change in the total merit index was h1.94 (s.e.50.42), which was not
different from the expectation of h2. This study, based on a large data set of commercial herds with accurate information
on profitability and genetic merit, confirms that, after accounting for confounding factors, the change in herd profitability per
unit change in herd genetic merit for the total merit index is within expectations
Risking It: An Examination of Risk Perception Amongst Obstetricians and Certified Professional Midwives in Missouri
The concept of risk is pervasive in contemporary discussions of childbirth –both amongst professionals and consumers. While risk is often presented as an objective entity, in reality it is an elusive concept to define, particularly within the context of maternity care. Since the nineteenth century, obstetricians and midwives have conceptualized the risks of birth differently. This thesis examines how two groups of practitioners in Missouri, obstetricians (OBs) and certified professional midwives (CPMs), perceive risk in pregnancy and childbirth. By combining archival investigation techniques with original qualitative research, I hope to demonstrate that risk in maternity care is far from a static concept. Rather, analyzing risk perception requires looking beyond individual knowledge systems to examine who it is that holds authoritative knowledge and how that knowledge drives definitions of risks and cultural understandings of what risks are acceptable during pregnancy and birth and what are not. After describing the history of maternity care in the United States, reviewing the relevant literature related to birth and risk perception, and presenting a qualitative study on the differences in risk perception between OBs and CPMs in Missouri, I move on to discuss the implications that differences and similarities in risk perception may have on the future of maternity care in Missouri
Asymptotic Dynamics in Quantum Field Theory
A crucial element of scattering theory and the LSZ reduction formula is the
assumption that the coupling vanishes at large times. This is known not to hold
for the theories of the Standard Model and in general such asymptotic dynamics
is not well understood. We give a description of asymptotic dynamics in field
theories which incorporates the important features of weak convergence and
physical boundary conditions. Applications to theories with three and four
point interactions are presented and the results are shown to be completely
consistent with the results of perturbation theory.Comment: 18 pages, 3 figure
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