152 research outputs found
Health hints for your horse (1993)
One of the real disappointments of horse ownership is planning a number of horse activities, then finding that your animal is physically incapable or mentally unwilling to engage in them. Horse owners who don't practice "preventive maintenance" may find themselves in this situation. This publication describes illnesses and injuries that horse owners should mindful of
The evolution of Runx genes I. A comparative study of sequences from phylogenetically diverse model organisms
BACKGROUND: Runx genes encode proteins defined by the highly conserved Runt DNA-binding domain. Studies of Runx genes and proteins in model organisms indicate that they are key transcriptional regulators of animal development. However, little is known about Runx gene evolution. RESULTS: A phylogenetically broad sampling of publicly available Runx gene sequences was collected. In addition to the published sequences from mouse, sea urchin, Drosophila melanogaster and Caenorhabditis elegans, we collected several previously uncharacterised Runx sequences from public genome sequence databases. Among deuterostomes, mouse and pufferfish each contain three Runx genes, while the tunicate Ciona intestinalis and the sea urchin Strongylocentrotus purpuratus were each found to have only one Runx gene. Among protostomes, C. elegans has a single Runx gene, while Anopheles gambiae has three and D. melanogaster has four, including two genes that have not been previously described. Comparative sequence analysis reveals two highly conserved introns, one within and one just downstream of the Runt domain. All vertebrate Runx genes utilize two alternative promoters. CONCLUSIONS: In the current public sequence database, the Runt domain is found only in bilaterians, suggesting that it may be a metazoan invention. Bilaterians appear to ancestrally contain a single Runx gene, suggesting that the multiple Runx genes in vertebrates and insects arose by independent duplication events within those respective lineages. At least two introns were present in the primordial bilaterian Runx gene. Alternative promoter usage arose prior to the duplication events that gave rise to three Runx genes in vertebrates
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Scaling in plasticity-induced cell-boundary microstructure: Fragmentation and rotational diffusion
We develop a simple computational model for cell-boundary evolution in plastic deformation. We study the cell-boundary size distribution and cell-boundary misorientation distribution that experimentally have been found to have scaling forms that are largely material independent. The cell division acts as a source term in the misorientation distribution which significantly alters the scaling form, giving it a linear slope at small misori- entation angles as observed in the experiments. We compare the results of our simulation with two closely related exactly solvable models that exhibit scaling behavior at late times: i fragmentation theory and ii a random walk in rotation space with a source term. We find that the scaling exponents in our simulation agree with those of the theories, and that the scaling collapses obey the same equations, but that the shape of the scaling functions depends upon the methods used to measure sizes and to weight averages and histograms.Physic
Scaling in Plasticity-Induced Cell-Boundary Microstructure: Fragmentation and Rotational Diffusion
We develop a simple computational model for cell boundary evolution in
plastic deformation. We study the cell boundary size distribution and cell
boundary misorientation distribution that experimentally have been found to
have scaling forms that are largely material independent. The cell division
acts as a source term in the misorientation distribution which significantly
alters the scaling form, giving it a linear slope at small misorientation
angles as observed in the experiments. We compare the results of our simulation
to two closely related exactly solvable models which exhibit scaling behavior
at late times: (i) fragmentation theory and (ii) a random walk in rotation
space with a source term. We find that the scaling exponents in our simulation
agree with those of the theories, and that the scaling collapses obey the same
equations, but that the shape of the scaling functions depend upon the methods
used to measure sizes and to weight averages and histograms
Grain boundary energies and cohesive strength as a function of geometry
Cohesive laws are stress-strain curves used in finite element calculations to
describe the debonding of interfaces such as grain boundaries. It would be
convenient to describe grain boundary cohesive laws as a function of the
parameters needed to describe the grain boundary geometry; two parameters in 2D
and 5 parameters in 3D. However, we find that the cohesive law is not a smooth
function of these parameters. In fact, it is discontinuous at geometries for
which the two grains have repeat distances that are rational with respect to
one another. Using atomistic simulations, we extract grain boundary energies
and cohesive laws of grain boundary fracture in 2D with a Lennard-Jones
potential for all possible geometries which can be simulated within periodic
boundary conditions with a maximum box size. We introduce a model where grain
boundaries are represented as high symmetry boundaries decorated by extra
dislocations. Using it, we develop a functional form for the symmetric grain
boundary energies, which have cusps at all high symmetry angles. We also find
the asymptotic form of the fracture toughness near the discontinuities at high
symmetry grain boundaries using our dislocation decoration model.Comment: 12 pages, 19 figures, changed titl
English in Wartime: A Symposium by College Teachers
After the declaration of war upon us by the Axis nations, it seemed the editors of College English that the members of the College should, as soon as possible, co-operate in determining how best to fulfil our special responsibility throughout World War II. As a first step, we invited twenty-five teachers of English in colleges and universities to suggest how we should meet this professional emergency.
The Planning Commission of the N.C.T.E., at their meeting in Chicago during the Christmas holidays, and the College Section, at their meeting in Indianapolis with the M.L.A., considered general and basic wartime policies for the National Council. The result of these deliberations will be presented in the March College English.
To assemble a preliminary survey of opinion on the teaching of English in World War II, we had to act quickly in order to meet the deadline for the February issue. Nine letters from college men and women came back in time to be included in the symposium. The weakness of the small number, however, is overcome by the strength of the unified and obviously representative character of the responses. Teachers of English believe in the permanent value of the work they are doing. In peace or in war the discipline of the humanities is a way to decency in human relations. Those who have written for the symposium agree that our time of emergency requires of us, as teachers of English, a more vigorous concentration than ever upon clear expression and broad, permanently vital reading.
We will need to make curriculum changes, and individually we will perform special wartime duties; but the initial message from outstanding college teachers is that we must do the job for which we are trained: help others to realize the power which emanates from great literature to live humanely in the midst of conflict
Heralded generation of entangled photon pairs
Entangled photons are a crucial resource for quantum communication and linear
optical quantum computation. Unfortunately, the applicability of many
photon-based schemes is limited due to the stochastic character of the photon
sources. Therefore, a worldwide effort has focused in overcoming the limitation
of probabilistic emission by generating two-photon entangled states conditioned
on the detection of auxiliary photons. Here we present the first heralded
generation of photon states that are maximally entangled in polarization with
linear optics and standard photon detection from spontaneous parametric
down-conversion. We utilize the down-conversion state corresponding to the
generation of three photon pairs, where the coincident detection of four
auxiliary photons unambiguously heralds the successful preparation of the
entangled state. This controlled generation of entangled photon states is a
significant step towards the applicability of a linear optics quantum network,
in particular for entanglement swapping, quantum teleportation, quantum
cryptography and scalable approaches towards photonics-based quantum computing
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