1,094 research outputs found
Deviation of the Nucleon Shape From Spherical Symmetry: Experimental Status
In this brief pedagogical overview the physical basis of the deviation of the
nucleon shape from spherical symmetry will be presented along with the
experimental methods used to determine it by the gamma* p -> Delta reaction.The
fact that significant non-spherical electric(E2) and Coulomb quadrupole(C2)
amplitudes have been observed will be demonstrated. These multipoles for the
N,Delta system as a function of Q^2 from the photon point through 4 GeV^2 have
been measured with modest precision. Their precise magnitude remains model
dependent due to the contributions of the background amplitudes, although rapid
progress is being made to reduce these uncertainties. A discussion of what is
required to perform a model independent analysis is presented. All of the data
to date are consistent with a prolate shape for the proton (larger at the
poles) and an oblate shape(flatter at the poles) for the Delta. It is suggested
here that the fundamental reason for this lies in the spontaneous breaking of
chiral symmetry in QCD and the resulting, long range(low Q^2), effects of the
pion cloud. This verification of this suggestion, as well as a more accurate
measurement of the deviation from spherical symmetry, requires further
experimental and theoretical effort.Comment: 8 pages, 8 figures, enhanced conference proceeding
Raytheon -- Strength Optimized Designs Using Additive Manufacturing
Designing a structure to demonstrate the strength of 3-D printed part is more complicated than it seems. The design goal was to construct a device that demonstrates how 3-D printing can create a strength optimized design. The design must incorporate maximum strength, while not sacrificing other major components such as weight of the product, cost of the product, print time of the product and how much material is being used. Extensive research and tests were conducted on infill patterns, football helmets, and TPU material (material used in football helmets).
There are multiple infill patterns that must be considered. The most important aspect of printing parts via FDM 3D printing is the infill pattern. This will directly affect the print time, material used, cost, and strength of the printed part. The second most important concept of the 3-D printed part is the infill structure. There are many infill structures, each having its own strengths and weaknesses when approaching higher strength, time to print, material used and weight. The team decided to focus on four commonly used infill structures (honeycomb, wiggle, triangular, and rectilinear). The team conducted a 3-point bending test and compression test, strictly following the ATSM standards to find out more about the strengths and weaknesses of each specific infill pattern (shown in this report). A design has been created and the application is a football Helmet. The design has 2 parts. The first part is a smaller, circular piece as the very top of the helmet. This piece contains a “triple layer infill sandwich.” The triple layer infill sandwich is composed of 3 different infills: wiggle infill (good for distributing rotational energy), honeycomb infill (good for distributing linear impact), wiggle infill again (good for distributing rotational energy). The second part of the helmet liner is a dome composed of an Isomax structure with a hole cut out at the top of the helmet.
The team originally came up with 120 different designs in an attempted to best solve the task at hand. The method from obtaining these ideas came from brainstorming and online research. To narrow the solutions, a table was made with different attributes and rankings with each attribute. The team went through each individual concept and ranked it accordingly. After we had our top ideas team 13 conducted specific testing to figure out which idea was best and team 13 came up with this specific helmet liner
Baryon octupole moments
We report on a calculation of higher electromagnetic multipole moments of
baryons in a non-covariant quark model approach. The employed method is based
on the underlying spin-flavor symmetry of the strong interaction and its
breaking.We present results on magnetic octupole moments of decuplet baryons
and discuss their implications.Comment: 3 page
Double polarization experiments at intermediate energy
At modern electron accelerators with highly polarized, intense, high duty
factor beams double polarization coincidence experiments became feasible with
good statistical accuracy. The strong potential towards the precise
determination of small nucleon structure quantities is illustrated by two
recent examples from MAMI. The measurement of in the quasifree reaction
lead to a new parametrization of which is
significantly above the previously preferred one from elastic scattering.
A experiment at the energy of the resonance
yields preliminary results for the longitudinal quadrupole mixing. Both
experimental errors and model uncertainties are complementary to unpolarized
measurements.Comment: 8 pages, 6 figures, plenary talk given at PANIC'9
Effectiveness of two Arthritis Foundation programs: Walk With Ease, and YOU Can Break the Pain Cycle
Objective: To evaluate the effectiveness of two Arthritis Foundation programs: Walk With Ease (WWE) and YOU Can Break The Pain Cycle (PC).
Design: Quasi-experimental, repeated measures design. Retested at six weeks and four months.
Setting: Community based intervention.
Participants: Volunteer sample of 163 adults with arthritis recruited through mailings, newspapers, and flyers.
Interventions: Subjects participated in a 90 minute seminar (PC, Group A), a six-week walking program (WWE, Group B), or both programs (Group C).
Main outcome measures: Survey assessment of arthritis knowledge, general health, selfmanagement activities, confidence, physical abilities, depression, health distress, and how arthritis affects their life. A Squat Test, a Six Minute Walk test, and a Timed Functional Walk Test were also administered.
Results: Subjects in Group B were more confident, less depressed, had less health distress, and less pain than subjects in Group A. Scores of Group C were between Group A and B scores. Differences in groups over time indicated that the WWE resulted in increased confidence, physical abilities, time spent in self-management activities and decreased pain and fatigue. All groups increased in walking endurance at six weeks, and increased in health distress at four months.
Conclusion: Subjects in different programs differed on impact of arthritis. These programs provide effective arthritis management opportunities
Constraints on the time-scale of nuclear breakup from thermal hard-photon emission
Measured hard photon multiplicities from second-chance nucleon-nucleon
collisions are used in combination with a kinetic thermal model, to estimate
the break-up times of excited nuclear systems produced in nucleus-nucleus
reactions at intermediate energies. The obtained nuclear break-up time for the
{Xe} + {Sn} reaction at 50{\it A} MeV is
100 -- 300 fm/ for all reaction centralities. The lifetime of the
radiating sources produced in seven other different heavy-ion reactions studied
by the TAPS experiment are consistent with 100 fm/,
such relatively long thermal photon emission times do not support the
interpretation of nuclear breakup as due to a fast spinodal process for the
heavy nuclear systems studied.Comment: 11 pages, 9 figures, submitted to EPJ
Offshell effects in electromagnetic reactions on the deuteron
Offshell contributions to the electromagnetic nuclear current are evaluated
within a nonrelativistic approach by incorporation one-pion loop contributions
in time-ordered perturbation theory. By construction, the correct experimental
onshell properties of the nucleon current are ensured so that only the genuine
offshell effects appear as model dependent. For a qualitative assessment of
such offshell effects, this model is applied to photodisintegration of the
deuteron for photon energies up to 500 MeV. While at low energies offshell
contributions are small, above 300 MeV they lead to sizeable effects in
observables up to about 30 percent pointing to the necessity of incorporating
such effects if one aims at theoretical predictions of high precision.Comment: 22 pages revtex including 17 figure
The Sumatra subduction zone: A case for a locked fault zone extending into the mantle
A current view is that the portion of the subduction interface that remains locked in the time interval between large interplate earthquakes, hereinafter referred to as the locked fault zone (LFZ), does not extend into the mantle because serpentinization of the mantle wedge would favor stable aseismic sliding. Here, we test this view in the case of the Sumatra subduction zone where the downdip end of the LFZ can be well constrained from the pattern and rate of uplift deduced from coral growth and from GPS measurements of horizontal deformation. These geodetic data are modeled from a creeping dislocation embedded in an elastic half-space and indicate that the LFZ extends 132 ± 10/7 km from the trench, to a depth between 35 and 57 km. By combining this information with the geometry of the plate interface as constrained from two-dimensional gravimetric modeling and seismicity, we show that the LFZ extends below the forearc Moho, which is estimated to lie at a depth of ~30 km, at a horizontal distance of 110 km from the trench. So, in this particular island arc setting, the LFZ most probably extends into the mantle, implying that either the mantle is not serpentinized, or that the presence of serpentine does not necessarily imply stable sliding. From thermal modeling, the temperature at the downdip end of the LFZ is estimated to be 260 ± 100°C. This temperature seems too low for thermally activated ductile flow, so that aseismic slip is most probably due to pressure and/or temperature induced steady state brittle sliding, possibly favored by fluids released from the subducting slab
Effective theory of the Delta(1232) in Compton scattering off the nucleon
We formulate a new power-counting scheme for a chiral effective field theory
of nucleons, pions, and Deltas. This extends chiral perturbation theory into
the Delta-resonance region. We calculate nucleon Compton scattering up to
next-to-leading order in this theory. The resultant description of existing
p cross section data is very good for photon energies up to about 300
MeV. We also find reasonable numbers for the spin-independent polarizabilities
and .Comment: 29 pp, 9 figs. Minor revisions. To be published in PR
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