9,052 research outputs found
A geometric basis for the standard-model gauge group
A geometric approach to the standard model in terms of the Clifford algebra
Cl_7 is advanced. A key feature of the model is its use of an algebraic spinor
for one generation of leptons and quarks. Spinor transformations separate into
left-sided ("exterior") and right-sided ("interior") types. By definition,
Poincare transformations are exterior ones. We consider all rotations in the
seven-dimensional space that (1) conserve the spacetime components of the
particle and antiparticle currents and (2) do not couple the right-chiral
neutrino. These rotations comprise additional exterior transformations that
commute with the Poincare group and form the group SU(2)_L, interior ones that
constitute SU(3)_C, and a unique group of coupled double-sided rotations with
U(1)_Y symmetry. The spinor mediates a physical coupling of Poincare and
isotopic symmetries within the restrictions of the Coleman--Mandula theorem.
The four extra spacelike dimensions in the model form a basis for the Higgs
isodoublet field, whose symmetry requires the chirality of SU(2). The charge
assignments of both the fundamental fermions and the Higgs boson are produced
exactly.Comment: 17 pages, LaTeX requires iopart. Accepted for publication in J. Phys.
A: Math. Gen. 9 Mar 2001. Typos correcte
Shining A Light On Galactic Outflows: Photo-Ionized Outflows
We study the ionization structure of galactic outflows in 37 nearby, star
forming galaxies with the Cosmic Origins Spectrograph on the Hubble Space
Telescope. We use the O I, Si II, Si III, and Si IV ultraviolet absorption
lines to characterize the different ionization states of outflowing gas. We
measure the equivalent widths, line widths, and outflow velocities of the four
transitions, and find shallow scaling relations between them and galactic
stellar mass and star formation rate. Regardless of the ionization potential,
lines of similar strength have similar velocities and line widths, indicating
that the four transitions can be modeled as a co-moving phase. The Si
equivalent width ratios (e.g. Si IV/Si II) have low dispersion, and little
variation with stellar mass; while ratios with O I and Si vary by a factor of 2
for a given stellar mass. Photo-ionization models reproduce these equivalent
width ratios, while shock models under predict the relative amount of high
ionization gas. The photo-ionization models constrain the ionization parameter
(U) between -2.25 < log(U) < -1.5, and require that the outflow metallicities
are greater than 0.5 Z. We derive ionization fractions for the
transitions, and show that the range of ionization parameters and stellar
metallicities leads to a factor of 1.15-10 variation in the ionization
fractions. Historically, mass outflow rates are calculated by converting a
column density measurement from a single metal ion into a total Hydrogen column
density using an ionization fraction, thus mass outflow rates are sensitive to
the assumed ionization structure of the outflow.Comment: 30 pages, 17 tables, 14 figures. Accepted for publication in MNRA
Oxford City PCG and PCT : a case study of collaboration
In 1997 the New Labour government instigated a period of radical reform for the National Health Service, a key element of which was the establishment across England of Primary Care Groups (PCGs), which subsequently became Primary Care Trusts (PCTs). These were local statutory governance bodies with responsibility to deliver and develop primary care and to improve the health of their local population: complex functions requiring collaboration with a range of organisations and agencies.
The central aim of this study was to investigate whether and how PCG/Ts developed and facilitated collaboration within primary care, and between it and other NHS and non-NHS bodies, and to identify factors which enabled and inhibited collaboration. Using a theoretical framework which draws on a critical realist tradition, an approach was adopted to the analysis of organisational change which was attentive not only to rational, incremental processes of change but which took into account the political, cultural and economic context in which PCG/Ts operated. A key element of this context was the strong resemblance between New Labour's prominent `third way' discourse of collaboration and the defining characteristics of a network mode of governance: trust, loyalty, reciprocity and voluntariness. Inductive and deductive approaches were combined to test and develop theory about the interactions between context and organisational form, using multiple qualitative methods within a longitudinal nested case study.
The study demonstrated that the locality-wide base of PCG/Ts, their explicit health improvement remit, budgetary arrangements and the presence of clinicians on their governing bodies were aspects of their organisational forms which equipped them to facilitate collaboration. However, over time, certain contradictions became apparent in New Labour's approach to organising the NHS which undermined many of the PCG/T's collaborative processes. This thesis argues that the alignment of the third way discourse with a network mode of governance exemplified 'symbolic politics. ' What was presented as a rational response to complex social problems and fragmentation of public services, was in fact largely a pragmatic political manoeuvre designed to distance itself from the perceived failure of previous administrations' hierarchy and market modes of governance
International Service-Learning: For A World of Difference
My friends who have graduated tell me that employers want to know what jobs I have held and whether they have been overseas. How can I do these things when in college? students ask
Service: The Intersection of Church and College
What does it mean to be a Church-related liberal arts college
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