30,699 research outputs found
Finitely annihilated groups
We say a group is finitely annihilated if it is the set-theoretic union of
all its proper normal finite index subgroups. We investigate this new property,
and observe that it is independent of several other well known group
properties. For finitely generated groups, we show that in many cases it is
equivalent to having non-cyclic abelianisation, and at the same time construct
an explicit infinite family of counterexamples to this. We show for finitely
presented groups that this property is neither Markov nor co-Markov. In the
context of our work we show that the weight of a non-perfect finite group, or a
non-perfect finitely generated solvable group, is the same as the weight of its
abelianisation. We generalise a theorem of Brodie-Chamberlain-Kappe on finite
coverings of groups, and finish with some generalisations and variations of our
new definition.Comment: 13 pages. This is the version submitted for publicatio
On gaugino condensation in the effective theory
We analyze the gaugino condensation in the effective theory for N=1 SU(N)
Supersymmetric QCD with flavors. It is known that taking the vacuum
expectation value of the matter field to be infinite, we can show that gaugino
condensation can occur. At such a limit we should consider only pure
supersymmetric Yang-Mills theory. But when we include an interaction term of
order , the situation can change. We analyze the effect of this
interaction term and examine the gaugino condensation in the low energy
Yang-Mills theory by using the scheme of Nambu-Jona-Lasinio.Comment: 5 pages, Plain Late
Probing the Effects of the Well-mixed Assumption on Viral Infection Dynamics
Viral kinetics have been extensively studied in the past through the use of
spatially well-mixed ordinary differential equations describing the time
evolution of the diseased state. However, emerging spatial structures such as
localized populations of dead cells might adversely affect the spread of
infection, similar to the manner in which a counter-fire can stop a forest fire
from spreading. In a previous publication (Beauchemin et al., 2005), a simple
2-D cellular automaton model was introduced and shown to be accurate enough to
model an uncomplicated infection with influenza A. Here, this model is used to
investigate the effects of relaxing the well-mixed assumption. Particularly,
the effects of the initial distribution of infected cells, the regeneration
rule for dead epithelial cells, and the proliferation rule for immune cells are
explored and shown to have an important impact on the development and outcome
of the viral infection in our model.Comment: LaTeX, 12 pages, 22 EPS figures, uses document class REVTeX 4, and
packages float, graphics, amsmath, and SIunit
A survey of UV-excess AGNs in the South Galactic Pole
Spectra, position, magnitudes and colors are presented for 485 faint (B<20.5)
emission line objects selected with the ultraviolet-excess (UVX) criterion on a
area of 24.6 sq. deg in the South Galactic Pole. The objects were selected from
the analysis of pixel-to-pixel stacking of COSMOS scans of UKST U, J and R
plates. The candidates were observed with the Meudon-ESO Fiber Optics System
(MEFOS) at the ESO 3.6m telescope. 429 type 1 AGNs have been identified (373 in
the redshift range 0.3<z<2.2). This sample has allowed the measure of a
difference on the QSO clustering evolution in comparison with that found for
galaxies (La Franca et al 1998). The region is part of the ESO Imaging Survey
(EIS) and of the 2dF QSO redshift survey.Comment: 32 pages, 19 figures. To appear on A&AS, revised after minor comment
The Effect of Agenda for Change on the Career Progression of the Radiographic Workforce 2009
Report compiled by the University of Hertfordshire in collaboration with the Inst for Employment Studies and Oxford Radcliffe Hospitals NHS Trust for the Society and College of RadiographersFinal Published versio
PDB36 DIFFERENCES IN EQ-5D SCORES FOR US AND UK-BASED PREFERENCE SCORING SYSTEMS IN PEOPLE WITH TYPE 2 DIABETES MELLITUS
On the use of satellite-derived frontal metrics in time series analyses of shelf-sea fronts, a study of the Celtic Sea
Satellite-derived frontal metrics describe characteristics of oceanic thermal fronts, such as their strength or persistence. They are used in marine science to investigate spatio-temporal variability of thermal fronts or in ecological studies to assist in explaining animal distributions. Although these metrics represent highly processed data, which is based on sometimes complex algorithms, little guidance is available on their correct application in quantitative analyses, in particular for non-specialist users. This research aims to improve accurate use of frontal data. This case study investigates the inter--annual and seasonal variability of two tidal mixing fronts on the Celtic Sea shelf, based on monthly time series of daily frontal maps at âŒ1km2 resolution from 1990 to 2010. Some metrics are almost identical and can be grouped, e.g. frontal probability, persistence and so-called âcompositesâ (Pearson correlation: râŻ=âŻ0.8â1.0; pâŻ<âŻ0.001), whereas the metric describing frontal strength is distinct from other ones. Consequently, strength and metrics of the frontal probability group showed pronounced differences in their inter-annual and seasonal variability: Strength displayed an oscillating pattern between 1990 and 2010 while there were no significant changes in probability over time. In addition, seasonal variability was affected by segments from adjacent fronts, not belonging to the fronts of interest, which could result in biased estimates. Most important, there was a doubling of available satellite imagery between 1990 and 2010 due to a greater number of operational satellites, which negatively affected frontal probability, positively frontal strength and consequently, changed the temporal pattern of both. When using frontal maps for temporal analyses, we should choose the metric carefully, be aware of biased estimates caused by variability from unwanted frontal segments in the data and account for the variable data quantity. This guide on the use of frontal metrics will be helpful to improve correct interpretations of statistical analyses
Tools for computing the AGN feedback: radio-loudness distribution and the kinetic luminosity function
We studied the Active Galactic Nuclei (AGN) radio emission from a compilation
of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of
more than 1600 AGN with 2-10 keV de-absorbed luminosities higher than 10^42
erg/s were used. For a sub-sample of about 50 z\lsim 0.1 AGN it was possible to
reach a ~80% fraction of radio detections and therefore, for the first time, it
was possible to almost completely measure the probability distribution function
of the ratio between the radio and the X-ray luminosity Rx=log[L(1.4)/Lx]. The
probability distribution function of Rx was functionally fitted as dependent on
the X-ray luminosity and redshift, P(Rx|Lx,z). It roughly spans over 6 decades
(-7<Rx<-1), and does not show any sign of bi-modality. It resulted that the
probability of finding large values of the Rx ratio increases with decreasing
X-ray luminosities and (possibly) with increasing redshift. No statistical
significant difference was found between the radio properties of the X-ray
absorbed and unabsorbed AGN. The measure of the probability distribution
function of Rx allowed us to compute the kinetic luminosity function and the
kinetic energy density which, at variance with what assumed in many galaxy
evolution models, is observed to decrease of about a factor of five at redshift
below 0.5. About half of the kinetic energy density results to be produced by
the more radio quiet (Rx<-4) AGN. In agreement with previous estimates, the AGN
efficiency in converting the accreted mass energy into kinetic power is, on
average, ~5x10-3.Comment: 13 pages, ApJsty; ApJ in pres
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