158 research outputs found
Experiential Learning Programs for the Future of Engineering Education
The need for 21st century engineers to be educated as creative innovators is discussed. Three complementary experiential learning programs that help engineering students learn to stretch beyond their comfort zones are described: a multidisciplinary design program; an entrepreneurship program; and an international engineering program. These three interdisciplinary programs each address common educational needs: to create flexible, creative, self-actualized change agents. The approaches we are taking to implement and institutionalize these in a large, comprehensive, research oriented university are described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86757/1/Sick5.pd
Determination of Matter Surface Distribution of Neutron-rich Nuclei
We demonstrate that the matter density distribution in the surface region is
determined well by the use of the relatively low-intensity beams that become
available at the upcoming radioactive beam facilities. Following the method
used in the analyses of electron scattering, we examine how well the density
distribution is determined in a model-independent way by generating pseudo data
and by carefully applying statistical and systematic error analyses. We also
study how the determination becomes deteriorated in the central region of the
density, as the quality of data decreases. Determination of the density
distributions of neutron-rich nuclei is performed by fixing parameters in the
basis functions to the neighboring stable nuclei. The procedure allows that the
knowledge of the density distributions of stable nuclei assists to strengthen
the determination of their unstable isotopes.Comment: 41 pages, latex, 27 figure
A Coherent Interpretation of the Form Factors of the Nucleon in Terms of a Pion Cloud and Constituent Quarks
The recent unbiased measurements of the electric form factor of the neutron
suggest that its shape may be interpreted as a smooth broad distribution with a
bump at Q^2 \approx 0.3(GeV/c)^2 superimposed. As a consequence the
corresponding charge distribution in the Breit frame shows a negative charge
extending as far out as 2fm. It is natural to identify this charge with the
pion cloud. This realisation is then used to reanalyse all old and new data of
the electric and magnetic from factors of the proton and the neutron by a
phenomenological fit and by a fit based on the constituent quark model. It is
shown that it is possible to fit all form factors coherently with both
ansaetzen and that they all show the signal of the pion cloud.Comment: 17 pages, 17 figure
EphB3 signaling propagates synaptic dysfunction in the traumatic injured brain
Traumatic brain injury (TBI), ranging from mild concussion to severe penetrating wounds, can involve brain regions that contain damaged or lost synapses in the absence of neuronal death. These affected regions significantly contribute to sensory, motor and/or cognitive deficits. Thus, studying the mechanisms responsible for synaptic instability and dysfunction is important for protecting the nervous system from the consequences of progressive TBI. Our controlled cortical impact (CCI) injury produces ~20% loss of synapses and mild changes in synaptic protein levels in the CA3-CA1 hippocampus without neuronal losses. These synaptic changes are associated with functional deficits, indicated by > 50% loss in synaptic plasticity and impaired learning behavior. We show that the receptor tyrosine kinase EphB3 participates in CCI injury-induced synaptic damage, where EphB3−/− mice show preserved long-term potentiation and hippocampal-dependent learning behavior as compared with wild type (WT) injured mice. Improved synaptic function in the absence of EphB3 results from attenuation in CCI injury-induced synaptic losses and reduced d-serine levels compared with WT injured mice. Together, these findings suggest that EphB3 signaling plays a deleterious role in synaptic stability and plasticity after TBI
Electromagnetic form factors of the bound nucleon
We calculate electromagnetic form factors of the proton bound in specified
orbits for several closed shell nuclei. The quark structure of the nucleon and
the shell structure of the finite nuclei are given by the QMC model. We find
that orbital electromagnetic form factors of the bound nucleon deviate
significantly from those of the free nucleon.Comment: 12 pages including 4 ps figure
Infinite Nuclear Matter on the Light Front: Nucleon-Nucleon Correlations
A relativistic light front formulation of nuclear dynamics is developed and
applied to treating infinite nuclear matter in a method which includes the
correlations of pairs of nucleons: this is light front Brueckner theory. We
start with a hadronic meson-baryon Lagrangian that is consistent with chiral
symmetry. This is used to obtain a light front version of a one-boson-exchange
nucleon-nucleon potential (OBEP). The accuracy of our description of the
nucleon-nucleon (NN) data is good, and similar to that of other relativistic
OBEP models. We derive, within the light front formalism, the Hartree-Fock and
Brueckner Hartree-Fock equations. Applying our light front OBEP, the nuclear
matter saturation properties are reasonably well reproduced. We obtain a value
of the compressibility, 180 MeV, that is smaller than that of alternative
relativistic approaches to nuclear matter in which the compressibility usually
comes out too large. Because the derivation starts from a meson-baryon
Lagrangian, we are able to show that replacing the meson degrees of freedom by
a NN interaction is a consistent approximation, and the formalism allows one to
calculate corrections to this approximation in a well-organized manner. The
simplicity of the vacuum in our light front approach is an important feature in
allowing the derivations to proceed. The mesonic Fock space components of the
nuclear wave function are obtained also, and aspects of the meson and nucleon
plus-momentum distribution functions are computed. We find that there are about
0.05 excess pions per nucleon.Comment: 39 pages, RevTex, two figure
Nucleon electromagnetic form factors
Elastic electromagnetic nucleon form factors have long provided vital
information about the structure and composition of these most basic elements of
nuclear physics. The form factors are a measurable and physical manifestation
of the nature of the nucleons' constituents and the dynamics that binds them
together. Accurate form factor data obtained in recent years using modern
experimental facilities has spurred a significant reevaluation of the nucleon
and pictures of its structure; e.g., the role of quark orbital angular
momentum, the scale at which perturbative QCD effects should become evident,
the strangeness content, and meson-cloud effects. We provide a succinct survey
of the experimental studies and theoretical interpretation of nucleon
electromagnetic form factors.Comment: Topical review invited by Journal of Physics G: Nuclear and Particle
Physics; 34 pages (contents listed on page 34), 11 figure
Modified Quark-Meson Coupling Model for Nuclear Matter
The quark-meson coupling model for nuclear matter, which describes nuclear
matter as non-overlapping MIT bags bound by the self-consistent exchange of
scalar and vector mesons, is modified by introducing medium modification of the
bag constant. We model the density dependence of the bag constant in two
different ways: one invokes a direct coupling of the bag constant to the scalar
meson field, and the other relates the bag constant to the in-medium nucleon
mass. Both models feature a decreasing bag constant with increasing density. We
find that when the bag constant is significantly reduced in nuclear medium with
respect to its free-space value, large canceling isoscalar Lorentz scalar and
vector potentials for the nucleon in nuclear matter emerge naturally. Such
potentials are comparable to those suggested by relativistic nuclear
phenomenology and finite-density QCD sum rules. This suggests that the
reduction of bag constant in nuclear medium may play an important role in low-
and medium-energy nuclear physics.Comment: Part of the text is reordered, revised version to appear in Phys.
Rev. C. 19 pages, ReVTeX, 4 figures embedde
Identification and characterisation of novel SNP markers in Atlantic cod: Evidence for directional selection
<p>Abstract</p> <p>Background</p> <p>The Atlantic cod (<it>Gadus morhua</it>) is a groundfish of great economic value in fisheries and an emerging species in aquaculture. Genetic markers are needed to identify wild stocks in order to ensure sustainable management, and for marker-assisted selection and pedigree determination in aquaculture. Here, we report on the development and evaluation of a large number of Single Nucleotide Polymorphism (SNP) markers from the alignment of Expressed Sequence Tag (EST) sequences in Atlantic cod. We also present basic population parameters of the SNPs in samples of North-East Arctic cod and Norwegian coastal cod obtained from three different localities, and test for SNPs that may have been targeted by natural selection.</p> <p>Results</p> <p>A total of 17,056 EST sequences were used to find 724 putative SNPs, from which 318 segregating SNPs were isolated. The SNPs were tested on Atlantic cod from four different sites, comprising both North-East Arctic cod (NEAC) and Norwegian coastal cod (NCC). The average heterozygosity of the SNPs was 0.25 and the average minor allele frequency was 0.18. <it>F</it><sub><it>ST </it></sub>values were highly variable, with the majority of SNPs displaying very little differentiation while others had <it>F</it><sub><it>ST </it></sub>values as high as 0.83. The <it>F</it><sub><it>ST </it></sub>values of 29 SNPs were found to be larger than expected under a strictly neutral model, suggesting that these loci are, or have been, influenced by natural selection. For the majority of these outlier SNPs, allele frequencies in a northern sample of NCC were intermediate between allele frequencies in a southern sample of NCC and a sample of NEAC, indicating a cline in allele frequencies similar to that found at the Pantophysin I locus.</p> <p>Conclusion</p> <p>The SNP markers presented here are powerful tools for future genetics work related to management and aquaculture. In particular, some SNPs exhibiting high levels of population divergence have potential to significantly enhance studies on the population structure of Atlantic cod.</p
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