2,546 research outputs found
Quark structure of pseudoscalar mesons
I review to which extent the properties of pseudoscalar mesons can be
understood in terms of the underlying quark (and eventually gluon) structure.
Special emphasis is put on the progress in our understanding of eta-eta'
mixing. Process-independent mixing parameters are defined, and relations
between different bases and conventions are studied. Both, the low-energy
description in the framework of Chiral Perturbation Theory and the high-energy
application in terms of light-cone wave functions for partonic Fock states, are
considered. A thorough discussion of theoretical and phenomenological
consequences of the mixing approach will be given. Finally, I will discuss
mixing with other states pi^0, eta(c), ...).Comment: 48 pages, 7 figures, using epsfig.st
Vector meson dominance and the rho meson
We discuss the properties of vector mesons, in particular the rho^0, in the
context of the Hidden Local Symmetry (HLS) model. This provides a unified
framework to study several aspects of the low energy QCD sector. Firstly, we
show that in the HLS model the physical photon is massless, without requiring
off field diagonalization. We then demonstrate the equivalence of HLS and the
two existing representations of vector meson dominance, VMD1 and VMD2, at both
tree level and one loop order. Finally the S matrix pole position is shown to
provide a model and process independent means of specifying the rho mass and
width, in contrast to the real axis prescription currently used in the Particle
Data Group tables.Comment: 18 pages, REVTE
The effects of symmetry on the dynamics of antigenic variation
In the studies of dynamics of pathogens and their interactions with a host
immune system, an important role is played by the structure of antigenic
variants associated with a pathogen. Using the example of a model of antigenic
variation in malaria, we show how many of the observed dynamical regimes can be
explained in terms of the symmetry of interactions between different antigenic
variants. The results of this analysis are quite generic, and have wider
implications for understanding the dynamics of immune escape of other
parasites, as well as for the dynamics of multi-strain diseases.Comment: 21 pages, 4 figures; J. Math. Biol. (2012), Online Firs
The medical student
The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine
Peer-led walking programme to increase physical activity in inactive 60- to 70-year-olds: Walk with Me pilot RCT
Background Levels of physical activity decline with age. Some of the most disadvantaged individuals in society, such as those with a lower rather than a higher socioeconomic position, are also the most inactive. Peer-led physical activity interventions may offer a model to increase physical activity in these older adults and thus help reduce associated health inequalities. This study aims to develop and test the feasibility of a peer-led, multicomponent physical activity intervention in socioeconomically disadvantaged community-dwelling older adults. Objectives The study aimed to develop a peer-led intervention through a rapid review of previous peer-led interventions and interviews with members of the target population. A proposed protocol to evaluate its effectiveness was tested in a pilot randomised controlled trial (RCT). Design A rapid review of the literature and the pilot study informed the intervention design; a pilot RCT included a process evaluation of intervention delivery. Setting Socioeconomically disadvantaged communities in the South Eastern Health and Social Care Trust and the Northern Health and Social Care Trust in Northern Ireland. Participants Fifty adults aged 60â70 years, with low levels of physical activity, living in socioeconomically disadvantaged communities, recruited though community organisations and general practices. Interventions âWalk with Meâ is a 12-week peer-led walking intervention based on social cognitive theory. Participants met weekly with peer mentors. During the initial period (weeks 1â4), each intervention group participant wore a pedometer and set weekly step goals with their mentorâs support. During weeks 5â8 participants and mentors met regularly to walk and discuss step goals and barriers to increasing physical activity. In the final phase (weeks 9â12), participants and mentors continued to set step goals and planned activities to maintain their activity levels beyond the intervention period. The control group received only an information booklet on active ageing. Main outcome measures Rates of recruitment, retention of participants and completeness of the primary outcome [moderate- and vigorous-intensity physical activity measured using an ActiGraph GT3X+ accelerometer (ActiGraph, LLC, Pensacola, FL, USA) at baseline, 12 weeks (post intervention) and 6 months]; acceptability assessed through interviews with participants and mentors. Results The study planned to recruit 60 participants. In fact, 50 eligible individuals participated, of whom 66% (33/50) were female and 80% (40/50) were recruited from general practices. At 6 months, 86% (43/50) attended for review, 93% (40/43) of whom returned valid accelerometer data. Intervention fidelity was assessed by using weekly step diaries, which were completed by both mentors and participants for all 12 weeks, and checklists for the level of delivery of intervention components, which was high for the first 3 weeks (range 49â83%). However, the rate of return of checklists by both mentors and participants diminished thereafter. Outcome data indicate that a sample size of 214 is required for a definitive trial. Limitations The sample was predominantly female and somewhat active. Conclusions The âWalk with Meâ intervention is acceptable to a socioeconomically disadvantaged community of older adults and a definitive RCT to evaluate its effectiveness is feasible. Some modifications are required to ensure fidelity of intervention delivery is optimised. Future research needs to identify methods to recruit males and less active older adults into physical activity interventions
A Quantitative Test of Hamilton's Rule for the Evolution of Altruism
A study of experimental evolution in simulated groups of foraging robots demonstrates that their propensity to behave altruistically depends on their genetic relatedness (similarity), and the costs and benefits associated with altruistic behavior
Comment on Spracklandus Hoser, 2009 (Reptilia, Serpentes, ELAPIDAE): request for confirmation of the availability of the generic name and for the nomenclatural validation of the journal in which it was published (Case 3601; see BZN 70: 234â237; 71: 30â38, 133â135, 181â182, 252â253)
1959: Abilene Christian College Bible Lectures - Full Text
UNTO ALL THE WORLDâ
Being the Abilene Christian College Annual Bible Lectures 1959
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