1,641 research outputs found
Amyotrophic Lateral Sclerosis: The Disease of the Peripheral Nervous System
A literary review of Amyotrophic Lateral Sclerosis summarizing the most up to date information about ALS. The most recent prevalence and incidence reports globally and specifically the USA are reported. Characteristics of the phenotypes are described and a break down of symptoms and effective diagnosis measures are reported and explained. Genetic and environmental factors are summarized and broken down in layman\u27s terms. Current research and treatments being performed for ALS patients and their future impacts are described
Quaternary Deposits Near the San Emigdio Mountains, California: Evidence for a Paleolandscape?
Discontinuous low-relief surfaces are scattered throughout relatively high topography within the San Emigdio Mountains, California. These surfaces are considered anomalous, as they are preserved in a dissected, mountainous region that is affected by ongoing orogeny. Previous research has suggested that the low-relief surfaces may represent a once-contiguous alluvial surface. This project utilizes field mapping and sedimentological analysis to determine if the surfaces represent a paleo landscape. What is apparent from field work is the presence of two morphologically distinct lithologic units that most likely represent surficial geologic components of the same relict landscape
The Nielsen Identities for the Two-Point Functions of QED and QCD
We consider the Nielsen identities for the two-point functions of full QCD
and QED in the class of Lorentz gauges. For pedagogical reasons the identities
are first derived in QED to demonstrate the gauge independence of the photon
self-energy, and of the electron mass shell. In QCD we derive the general
identity and hence the identities for the quark, gluon and ghost propagators.
The explicit contributions to the gluon and ghost identities are calculated to
one-loop order, and then we show that the quark identity requires that in
on-shell schemes the quark mass renormalisation must be gauge independent.
Furthermore, we obtain formal solutions for the gluon self-energy and ghost
propagator in terms of the gauge dependence of other, independent Green
functions.Comment: 25 pages, plain TeX, 4 figures available upon request, MZ-TH/94-0
D=2 gluon condensate and QCD propagators at finite temperature
We calculate the dimension two gluon condensate contribution to quark, gluon
and ghost propagators at finite temperature.Comment: Minor modifications. Accepted in PL
Management Research on Multinational Corporations: A Methodological Critique
In the context of burgeoning research on multinational corporations (MNCs), this paper addresses the issue of the representativeness of databases of MNCs in Ireland. It identifies some important deficiencies in existing databases much used by scholars in the field. Drawing on the international literature, it finds that this problem also characterises research on MNCs in many other countries. In the Irish context, we find that the extant empirical research has generally excluded two key categories of MNCs, namely, (a) foreign MNCs which are not grant-aided by the main industrial promotions agencies and (b) Irish-owned MNCs. The paper outlines our experience in identifying and addressing these deficiencies and describes the methods that might be employed in more precisely defining the MNC population in Ireland. More generally the paper reviews some of the issues and obstacles confronting scholars investigating the MNC sector in Ireland and abroad.
Collinearity, convergence and cancelling infrared divergences
The Lee-Nauenberg theorem is a fundamental quantum mechanical result which
provides the standard theoretical response to the problem of collinear and
infrared divergences. Its argument, that the divergences due to massless
charged particles can be removed by summing over degenerate states, has been
successfully applied to systems with final state degeneracies such as LEP
processes. If there are massless particles in both the initial and final
states, as will be the case at the LHC, the theorem requires the incorporation
of disconnected diagrams which produce connected interference effects at the
level of the cross-section. However, this aspect of the theory has never been
fully tested in the calculation of a cross-section. We show through explicit
examples that in such cases the theorem introduces a divergent series of
diagrams and hence fails to cancel the infrared divergences. It is also
demonstrated that the widespread practice of treating soft infrared divergences
by the Bloch-Nordsieck method and handling collinear divergences by the
Lee-Nauenberg method is not consistent in such cases.Comment: 29 pages, 17 figure
Recommended from our members
Threats to safe transitions from hospital to home: a consensus study in North West London primary care.
BACKGROUND: Transitions between healthcare settings are vulnerable points for patients. AIM: To identify key threats to safe patient transitions from hospital to primary care settings. DESIGN AND SETTING: Three-round web-based Delphi consensus process among clinical and non-clinical staff from 39 primary care practices in North West London, England. METHOD: Round 1 was a free-text idea-generating round. Rounds 2 and 3 were consensus-obtaining rating rounds. Practices were encouraged to complete the questionnaires at team meetings. Aggregate ratings of perceived level of importance for each threat were calculated (1-3: 'not important', 4-6: 'somewhat important', 7-9: 'very important'). Percentage of votes cast for each patient or medication group were recorded; consensus was defined as ≥75%. RESULTS: A total of 39 practices completed round 1, 36/39 (92%) completed round 2, and 30/36 (83%) completed round 3. Round 1 identified nine threats encompassing problems involving communication, service organisation, medication provision, and patients who were most at risk. 'Poor quality of handover instructions from secondary to primary care teams' achieved the highest rating (mean rating at round 3 = 8.43) and a 100% consensus that it was a 'very important' threat. Older individuals (97%) and patients with complex medical problems taking >5 medications (80%) were voted the most vulnerable. Anticoagulants (77%) were considered to pose the greatest risk to patients. CONCLUSION: This study identified specific threats to safe patient transitions from hospital to primary care, providing policymakers and healthcare providers with targets for quality improvement strategies. Further work would need to identify factors underpinning these threats so that interventions can be tailored to the relevant behavioural and environmental contexts in which these threats arise
Infra-Red Finite Charge Propagation
The Coulomb gauge has a long history and many uses. It is especially useful
in bound state applications. An important feature of this gauge is that the
matter fields have an infra-red finite propagator in an on-shell
renormalisation scheme. This is, however, only the case if the renormalisation
point is chosen to be the static point on the mass shell, p = (m, 0, 0, 0). In
this letter we show how to extend this key property of the Coulomb gauge to an
arbitrary relativistic renormalisation point. This is achieved through the
introduction of a new class of gauges of which the Coulomb gauge is a limiting
case. A physical explanation for this result is given.Comment: 8 pages, plain TeX, to appear in Modern Physics Letters
Gluon Condensate and Non-Perturbative Quark-Photon Vertex
We evaluate the quark-photon vertex non-perturbatively taking into account
the gluon condensate at finite temperature. This vertex is related to the
previously derived effective quark propagator by a QED like Ward-Takahashi
identity. The importance of the effective vertex for the dilepton production
rate from a quark-gluon plasma is stressed.Comment: 9 pages including two figure
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
- …