1,578 research outputs found
The rank of the semigroup of transformations stabilising a partition of a finite set
Let be a partition of a finite set . We say that a full
transformation preserves (or stabilizes) the partition
if for all there exists such that
. Let denote the semigroup of all full
transformations of that preserve the partition .
In 2005 Huisheng found an upper bound for the minimum size of the generating
sets of , when is a partition in which all of
its parts have the same size. In addition, Huisheng conjectured that his bound
was exact. In 2009 the first and last authors used representation theory to
completely solve Hisheng's conjecture.
The goal of this paper is to solve the much more complex problem of finding
the minimum size of the generating sets of , when
is an arbitrary partition. Again we use representation theory to
find the minimum number of elements needed to generate the wreath product of
finitely many symmetric groups, and then use this result to solve the problem.
The paper ends with a number of problems for experts in group and semigroup
theories
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Hydrologic Data for Urban Studies in the Austin, Texas Metropolitan Area, 1980
This report includes drainage basin maps and information from a specific storm (May 12, 1980) for the 23rd and 38th street Waller Creek locations.Waller Creek Working Grou
A New Metaheuristic Bat-Inspired Algorithm
Metaheuristic algorithms such as particle swarm optimization, firefly
algorithm and harmony search are now becoming powerful methods for solving many
tough optimization problems. In this paper, we propose a new metaheuristic
method, the Bat Algorithm, based on the echolocation behaviour of bats. We also
intend to combine the advantages of existing algorithms into the new bat
algorithm. After a detailed formulation and explanation of its implementation,
we will then compare the proposed algorithm with other existing algorithms,
including genetic algorithms and particle swarm optimization. Simulations show
that the proposed algorithm seems much superior to other algorithms, and
further studies are also discussed.Comment: 10 pages, 2 figure
Can osteophagia provide giraffes with phosphorus and calcium?
The daily requirement for calcium and phosphorus by giraffes to sustain the growth and maintenance of their skeletons is large. The source of sufficient calcium is browse. The source of necessary phosphorus is obscure, but it could be osteophagia, a frequently observed behaviour in giraffes. We have assessed whether bone ingested as a result of osteophagia can be digested in the rumen. Bone samples from cancellous (cervical vertebrae) and dense bones (metacarpal shaft) were immersed in the rumens of five sheep, for a period of up to 30 days, and the effect compared to immersion in distilled water and in artificial saliva for 30 days. Distilled water had no effect on the bones. Dense bone samples were softened by exposure to the saliva and rumen fluid, but did not lose either calcium or phosphorus. In saliva and rumen fluid the cancellous bone samples also softened, and their mass and volume decreased as a result of exposure to saliva, but in neither fluid did they lose significant amounts of calcium and phosphorus. We conclude that although saliva and rumen fluid can soften ingested bones, there is an insignificant digestion of bones in the rumen
The effects of graded levels of calorie restriction : II. Impact of short term calorie and protein restriction on circulating hormone levels, glucose homeostasis and oxidative stress in male C57BL/6 mice
This work was supported by BBSRC BB009953/1 awarded to JRS and SEM. PK and CD were funded by the Erasmus exchange programme. JRS, SEM, DD, CG, LC, JJDH, YW, DELP, DL and AD are members of the BBSRC China Partnership Award, BB/J020028/1.Peer reviewedPublisher PD
Achieving Health Equity in Embedded Pragmatic Trials for People Living with Dementia and Their Family Caregivers
Embedded pragmatic clinical trials (ePCTs) advance research on Alzheimer's disease/Alzheimer's disease and related dementias (AD/ADRD) in real-world contexts; however, health equity issues have not yet been fully considered, assessed, or integrated into ePCT designs. Health disparity populations may not be well represented in ePCTs without special efforts to identify and successfully recruit sites of care that serve larger numbers of these populations. The National Institute on Aging (NIA) Imbedded Pragmatic Alzheimer's disease (AD) and AD-Related Dementias (AD/ADRD) Clinical Trials (IMPACT) Collaboratory's Health Equity Team will contribute to the overall mission of the collaboratory by developing and implementing strategies to address health equity in the conduct of ePCTs and ensure the collaboratory is a national resource for all Americans with dementia. As a first step toward meeting these goals, this article reviews what is currently known about the inclusion of health disparities populations of people living with dementia (PLWD) and their caregivers in ePCTs, highlights unique challenges related to health equity in the conduct of ePCTs, and suggests priority areas in the design and implementation of ePCTs to increase the awareness and avoidance of pitfalls that may perpetuate and magnify healthcare disparities
Nucleotide Frequencies in Human Genome and Fibonacci Numbers
This work presents a mathematical model that establishes an interesting
connection between nucleotide frequencies in human single-stranded DNA and the
famous Fibonacci's numbers. The model relies on two assumptions. First,
Chargaff's second parity rule should be valid, and, second, the nucleotide
frequencies should approach limit values when the number of bases is
sufficiently large. Under these two hypotheses, it is possible to predict the
human nucleotide frequencies with accuracy. It is noteworthy, that the
predicted values are solutions of an optimization problem, which is commonplace
in many nature's phenomena.Comment: 12 pages, 2 figure
Allometric analysis of the giraffe cardiovascular system
There has been co-evolution of a long neck and high blood pressure in giraffes. How the cardiovascular
system (CVS) has adapted to produce a high blood pressure, and how it compares with other similar sized
mammals largely is unknown. We have measured body mass and heart structure in 56 giraffes of both
genders ranging in body mass from 18 kg to 1500 kg, and developed allometric equations that relate changes
in heart dimensions to growth and to cardiovascular function. Predictions made from these equations match
measurements made in giraffes. We have found that heart mass increases as body mass increases but it has a
relative mass of 0.51±0.7% of body mass which is the same as that in other mammals. The left ventricular
and interventricular walls are hypertrophied and their thicknesses are linearly related to neck length.
Systemic blood pressure increases as body mass and neck length increase and is twice that of mammals of
the same body mass. Cardiac output is the same as, but peripheral resistance double that predicted for
similar sized mammals. We have concluded that increasing hydrostatic pressure of the column of blood
during neck elongation results in cardiac hypertrophy and concurrent hypertrophy of arteriole walls raising
peripheral resistance, with an increase in blood pressure following.The Bubye Valley
Conservancy, Zimbabwe and the Don Craib Trust
(JDS), from a personal research grant (JDS) and the University of
Wyoming (GM).http://www.elsevier.com/locate/cbpamn201
A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La
An apparatus for measuring parity-violating asymmetries in gamma-ray emission
following polarized cold neutron capture was constructed as a 1/10th scale test
of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The
elements of the polarized neutron beam, including a polarized 3He neutron spin
filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl)
detectors and photodiode current mode readout, measurements were made of
asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and
139La targets. Upper limits on the parity-allowed asymmetry were set at the level of 7 x 10^-6 for all three
targets. Parity-violating asymmetries were observed in
35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x
10^-6, values consistent with previous measurements.Comment: 19 pages, 4 figures, submitted to Nucl. Instr. and Meth.
Parity Nonconservation in Neutron Resonances in 133Cs
Spatial parity nonconservation (PNC) has been studied in the compound-nuclear states of 134Cs by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick 133Cs target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range from 5 to 400 eV. A total of 28 new p-wave resonances were found, their neutron widths determined, and the PNC longitudinal asymmetries of the resonance cross sections measured. The value obtained for the root-mean-square PNC element M=(0.06-0.02+0.25) meV in 133Cs is the smallest among all targets studied. This value corresponds to a weak spreading width Îw=(0.006-0.003+0.154)Ă10-7 eV
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