807 research outputs found
Spin asymmetries for confined Dirac particles
We study the Bjorken `x' (or equivalently Nachtmann `xi') dependence of the
virtual photon spin asymmetry in polarized deep inelastic scattering of
electrons from hadrons. We use an exactly solved relativistic potential model
of the hadron, treating the constituents as independent massless Dirac
particles confined to an infinitely massive force center. The importance of
including the p-wave components of the Dirac wave function is demonstrated.
Comparisons are made to the observed data on the proton by taking into account
the observed flavor dependence of the valence quark distribution functions.Comment: 4 pages, 4 figues; submitted to Phys. Lett.
Apicoetomy and Root Canal Therapy of Canine Teeth in the Dog
When the root canal of the canine tooth of a dog is exposed due to wear or fracture, the result may be abscessation, bone resorption, and evulsion of the alveolus. The tooth must be extracted or endodontic therapy may be performed to restore the root canal. Techniques are described to stabilize both maxillary and mandibular canine teeth through root canal restoration and apicoectomy to seal the apex of the root and prevent future infection and abcessation
EEGgui: a program used to detect electroencephalogram anomalies after traumatic brain injury
BACKGROUND: Identifying and quantifying pathological changes in brain electrical activity is important for investigations of brain injury and neurological disease. An example is the development of epilepsy, a secondary consequence of traumatic brain injury. While certain epileptiform events can be identified visually from electroencephalographic (EEG) or electrocorticographic (ECoG) records, quantification of these pathological events has proved to be more difficult. In this study we developed MATLAB-based software that would assist detection of pathological brain electrical activity following traumatic brain injury (TBI) and present our MATLAB code used for the analysis of the ECoG. METHODS: Software was developed using MATLAB(â„¢) and features of the open access EEGLAB. EEGgui is a graphical user interface in the MATLAB programming platform that allows scientists who are not proficient in computer programming to perform a number of elaborate analyses on ECoG signals. The different analyses include Power Spectral Density (PSD), Short Time Fourier analysis and Spectral Entropy (SE). ECoG records used for demonstration of this software were derived from rats that had undergone traumatic brain injury one year earlier. RESULTS: The software provided in this report provides a graphical user interface for displaying ECoG activity and calculating normalized power density using fast fourier transform of the major brain wave frequencies (Delta, Theta, Alpha, Beta1, Beta2 and Gamma). The software further detects events in which power density for these frequency bands exceeds normal ECoG by more than 4 standard deviations. We found that epileptic events could be identified and distinguished from a variety of ECoG phenomena associated with normal changes in behavior. We further found that analysis of spectral entropy was less effective in distinguishing epileptic from normal changes in ECoG activity. CONCLUSION: The software presented here was a successful modification of EEGLAB in the Matlab environment that allows detection of epileptiform ECoG signals in animals after TBI. The code allows import of large EEG or ECoG data records as standard text files and uses fast fourier transform as a basis for detection of abnormal events. The software can also be used to monitor injury-induced changes in spectral entropy if required. We hope that the software will be useful for other investigators in the field of traumatic brain injury and will stimulate future advances of quantitative analysis of brain electrical activity after neurological injury or disease
Laser Applications to Chemical and Environmental Analysis: Introduction to the Feature Issue
This issue of Applied Optics features 16 papers describing chemical and environmental measurements made possible by lasers. Many of these contributions were presented at the Optical Society of America Topical Meeting on Laser Applications to Chemical and Environmental Analysis, held in Orlando, Florida, 9–11 March 1998.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86759/1/Sick33.pd
Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei
Superscaling analyses of few-GeV inclusive electron scattering from nuclei
are extended to include not only quasielastic processes, but now also into the
region where -excitation dominates. It is shown that, with reasonable
assumptions about the basic nuclear scaling function extracted from data and
information from other studies of the relative roles played by correlation and
MEC effects, the residual strength in the resonance region can be accounted for
through an extended scaling analysis. One observes scaling upon assuming that
the elementary cross section by which one divides the residual to obtain a new
scaling function is dominated by the transition and employing a
new scaling variable which is suited to the resonance region. This yields a
good representation of the electromagnetic response in both the quasielastic
and regions. The scaling approach is then inverted and predictions are
made for charge-changing neutrino reactions at energies of a few GeV, with
focus placed on nuclei which are relevant for neutrino oscillation
measurements. For this a relativistic treatment of the required weak
interaction vector and axial-vector currents for both quasielastic and
-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review
Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors
In the light of the new data on the various neutron and proton
electromagnetic form factors taken in recent years, we update the
dispersion-theoretical analysis of the nucleon electromagnetic form factors
from the mid-nineties. The parametrization of the spectral functions includes
constraints from unitarity, perturbative QCD, and recent measurements of the
neutron charge radius. We obtain a good description of most modern form factor
data, with the exception of the Jefferson Lab data on G_E^p/G_M^p in the
four-momentum transfer range Q^2=3...6 GeV^2. For the magnetic radii of the
proton and the neutron we find r_M^p = 0.857 fm and r_M^n = 0.879 fm, which is
consistent with the recent determinations using continued fraction expansions.Comment: 5 pages, 3 ps figures, final version, exp. errors in Figs. 1 and 3
correcte
The size of the proton - closing in on the radius puzzle
We analyze the recent electron-proton scattering data from Mainz using a
dispersive framework that respects the constraints from analyticity and
unitarity on the nucleon structure. We also perform a continued fraction
analysis of these data. We find a small electric proton charge radius, r_E^p =
0.84_{-0.01}^{+0.01} fm, consistent with the recent determination from muonic
hydrogen measurements and earlier dispersive analyses. We also extract the
proton magnetic radius, r_M^p = 0.86_{-0.03}^{+0.02} fm, consistent with
earlier determinations based on dispersion relations.Comment: 4 pages, 2 figures, fit improved, small modifications, section on
continued fractions modified, conclusions on the proton charge radius
unchanged, version accepted for publication in European Physical Journal
Role of Non-Stationary Collisional Dynamics in Determining Nitric Oxide LIF Spectra
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77182/1/AIAA-2004-389-525.pd
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