976 research outputs found
All electromagnetic form factors
The electromagnetic form factors of spin-1/2 particles are known, but due to
historical reasons only half of them are found in many textbooks. Given the
importance of the general result, its model independence, its connection to
discrete symmetries and their violations we made an effort to derive and
present the general result based only on the knowledge of Dirac equation. We
discuss the phenomenology connected directly with the form factors, and spin
precession in external fields including time reversal violating terms. We apply
the formalism to spin-flip synchrotron radiation and suggest pedagogical
projects.Comment: Latex, 22 page
A performance comparison of two small rocket nozzles
An experimental study was conducted on two small rockets (110 N thrust class) to directly compare a standard conical nozzle with a bell nozzle optimized for maximum thrust using the Rao method. In large rockets, with throat Reynolds numbers of greater than 1 x 10(exp 5), bell nozzles outperform conical nozzles. In rockets with throat Reynolds numbers below 1 x 10(exp 5), however, test results have been ambiguous. An experimental program was conducted to test two small nozzles at two different fuel film cooling percentages and three different chamber pressures. Test results showed that for the throat Reynolds number range from 2 x 10(exp 4) to 4 x 10(exp 4), the bell nozzle outperformed the conical nozzle. Thrust coefficients for the bell nozzle were approximately 4 to 12 percent higher than those obtained with the conical nozzle. As expected, testing showed that lowering the fuel film cooling increased performance for both nozzle types
Perceptions of School and Health Department Emergency Preparedness Collaboration
Background: School systems often have the vital responsibility of protecting students during emergency situations. Collaborations with the local health department (LHD) can be invaluable in helping schools effectively fulfill this responsibility.
Purpose: An evaluation of existing organizational collaborations is needed to describe attitudes toward current efforts and to form recommendations for enhancing the effectiveness of future joint programs.
Methods: Questionnaires regarding perceptions of existing collaborations were distributed to a sample of LHDs and schools districts in spring and summer 2011. Participant responses from each organization were paired on jurisdictional area, forming 25 paired observations. Analyses were conducted in early 2012. Descriptive statistics of selected variables were computed and differences between paired LHD and school district responses were analyzed.
Results: Results showed that school districts and LHDs both rated engagement between organizations in emergency preparedness as extremely important. Each gave high ratings on success and satisfaction of current efforts. Organizations had significant differences in ratings measuring their agreement with specific collaboration drawbacks.
Implications: These results suggest the potential for extended and enhanced collaborations, although future programs might be most effectively implemented when tailored to limit the perceived drawbacks of individual organizations. Continued and improved collaborations between school districts and their local health departments will help to increase the school systems’ abilities to adequately prepare for and respond to the needs of the children they serve in the event of an emergency
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
Two-Boson Exchange Physics: A Brief Review
Current status of the two-boson exchange contributions to elastic
electron-proton scattering, both for parity conserving and parity-violating, is
briefly reviewed. How the discrepancy in the extraction of elastic nucleon form
factors between unpolarized Rosenbluth and polarization transfer experiments
can be understood, in large part, by the two-photon exchange corrections is
discussed. We also illustrate how the measurement of the ratio between
positron-proton and electron-proton scattering can be used to differentiate
different models of two-photon exchange. For the parity-violating
electron-proton scattering, the interest is on how the two-boson exchange
(TBE), \gamma Z-exchange in particular, could affect the extraction of the
long-sought strangeness form factors. Various calculations all indicate that
the magnitudes of effect of TBE on the extraction of strangeness form factors
is small, though can be large percentage-wise in certain kinematics.Comment: 6 pages, 5 figures, prepared for Proceedings of the fifth
Asia-Pacific Conference on Few-Body Problems in Physics (APFB2011), Seoul,
Korea, August 22-26, 2011, to appear in Few-Body Systems, November 201
Nucleon Form Factors - A Jefferson Lab Perspective
The charge and magnetization distributions of the proton and neutron are
encoded in their elastic electromagnetic form factors, which can be measured in
elastic electron--nucleon scattering. By measuring the form factors, we probe
the spatial distribution of the proton charge and magnetization, providing the
most direct connection to the spatial distribution of quarks inside the proton.
For decades, the form factors were probed through measurements of unpolarized
elastic electron scattering, but by the 1980s, progress slowed dramatically due
to the intrinsic limitations of the unpolarized measurements. Early
measurements at several laboratories demonstrated the feasibility and power of
measurements using polarization degrees of freedom to probe the spatial
structure of the nucleon. A program of polarization measurements at Jefferson
Lab led to a renaissance in the field of study, and significant new insight
into the structure of matter.Comment: 20 pages, 9 figures; Chapter in the book "A decade of Physics at
Jefferson Lab", to be published in Journal of Physics: Conference Serie
DonorNet and the Potential Effects on Organ Utilization
The evolution of communication as donor data flows from organ procurement organization to transplant centers has evolved with the incorporation of DonorNet 2007 ® into the UNet SM system. The ensuing study looks at DonorNet's impact on this process. We established defined time periods for comparison purposes. The study looked at match number for organ placement and overall organ utilization with a focus on ischemia time and graft outcomes. The results of the study demonstrate no significant change in the median match number of organ placement in liver or kidney transplantation. Changes in discard rates were varied amongst transplanted organs and there were noticeable changes in organ sharing with an increase in local allocation for kidney and liver and an ensuing decrease in regional and national distribution. There were no significant differences in the outcomes of livers and kidneys with low offer numbers compared with those with high offer numbers. Overall the study suggests a modest impact by DonorNet on organ placement and utilization, but a longer term study would need to be done to fully evaluate its impact.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79141/1/j.1600-6143.2010.03036.x.pd
Response: DonorNet and the Potential Effects on Organ Utilization
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79092/1/j.1600-6143.2010.03230.x.pd
Fluency Assistance Device
Currently about 1% of the world population (~70 million people) have a stutter considered a fluency disorder. Some fluency assistance devices are available for this population, but most are highly expensive or unreliable. Fluency Assistance Device (FAD) seeks to assist a niche community of these individuals for whom therapy has been unsuccessful but are currently depending on a device originally known as the Edinburgh Masker. FAD aims to redesign the masker to be more comfortable for the end user. FAD is developing versions 1.1 and 2.0 of the improved masker. Version 1.1 will update the original masker circuitry with surface mount devices. This will allow a slimmer circuitry enclosure, and enable upgrades of the original as requested. Version 2.0 will use Bluetooth technology and a microcontroller to achieve masker functionality with software code. FAD is now finalizing Version 1.1 and beginning Version 2.0.https://mosaic.messiah.edu/engr2020/1008/thumbnail.jp
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