1,819 research outputs found
Generalized Relativistic Meson Wave Function
We study the most general, relativistic, constituent meson
wave function within a new covariant framework. We find that by including a
tensor wave function component, a pure valence quark model is now capable of
reproducing not only all static pion data (, )
but also the distribution amplitude, form factor , and structure
functions. Further, our generalized spin wave function provides a much better
detailed description of meson properties than models using a simple
relativistic extension of the nonrelativistic wave function.Comment: 17 pages, REXTeX 3.0 file, (uuencoded postscript files of 8 figures
appended
Quark-hadron duality in a relativistic, confining model
Quark-hadron duality is an interesting and potentially very useful
phenomenon, as it relates the properly averaged hadronic data to a perturbative
QCD result in some kinematic regions. While duality is well established
experimentally, our current theoretical understanding is still incomplete. We
employ a simple model to qualitatively reproduce all the features of
Bloom-Gilman duality as seen in electron scattering. In particular, we address
the role of relativity, give an explicit analytic proof of the equality of the
hadronic and partonic scaling curves, and show how the transition from coherent
to incoherent scattering takes place.Comment: This paper is dedicated to the memory of our collaborator Nathan
Isgur. (34 pages, 13 figures
Modeling quark-hadron duality for relativistic, confined fermions
We discuss a model for the study of quark-hadron duality in inclusive
electron scattering based on solving the Dirac equation numerically for a
scalar confining linear potential and a vector color Coulomb potential. We
qualitatively reproduce the features of quark-hadron duality for all potentials
considered, and discuss similarities and differences to previous models that
simplified the situation by treating either the quarks or all particles as
scalars. We discuss the scaling results for PWIA and FSI, and the approach to
scaling using the analog of the Callan-Gross relation for y-scaling.Comment: 38 pages, 21 figure
Planetary Migration and Extrasolar Planets in the 2/1 Mean-Motion Resonance
We analyze the possible relationship between the current orbital elements
fits of known exoplanets in the 2/1 mean-motion resonance and the expected
orbital configuration due to migration. It is found that, as long as the
orbital decay was sufficiently slow to be approximated by an adiabatic process,
all captured planets should be in apsidal corotations. In other words, they
should show a simultaneous libration of both the resonant angle and the
difference in longitudes of pericenter.
We present a complete set of corotational solutions for the 2/1
commensurability, including previously known solutions and new results.
Comparisons with observed exoplanets show that current orbital fits of three
known planetary systems in this resonance are either consistent with apsidal
corotations (GJ876 and HD82943) or correspond to bodies with uncertain orbits
(HD160691).
Finally, we discuss the applicability of these results as a test for the
planetary migration hypothesis itself. If all future systems in this
commensurability are found to be consistent with corotational solutions, then
resonance capture of these bodies through planetary migration is a working
hypothesis. Conversely, If any planetary pair is found in a different
configuration, then either migration did not occur for those bodies, or it took
a different form than currently believed.Comment: Submitted to MNRA
Plasma Factor XIII Activity in Patients with Disseminated Intravascular Coagulation
The objective of this study was to investigate the correlation between factor XIII (FXIII) activity and disseminated intravascular coagulation (DIC) parameters and also to evaluate the clinical usefulness of DIC diagnosis. Citrated plasma from eighty patients with potential DIC was analyzed for FXIII activity. The primary patient conditions (48 male and 32 female, mean age, 51 years) were malignancy (n = 29), infection (n = 25), inflammation (n = 6), heart disease (n = 3), thrombosis (n = 2), injury (n = 2), and other miscellaneous conditions (n = 13). FXIII testing was performed using the CoaLinkTM FXIII Incorporation Assay Kit (PeopleBio Inc.). Among 80 patients who were suspected to have DIC based on clinical analysis, 46 (57.5%) fulfilled the overt DIC criteria (DIC score > = 5) according to the International Society of Thrombosis and Haemostasis. FXIII levels in the plasma were significantly decreased in overt DIC compared to non-overt DIC patients (mean 75.1% and 199.7% respectively, p < 0.0001). Interestingly, we found a significant inverse correlation between DIC scores and FXIII activity. In addition, FXIII activity significantly correlated with other hemostatic markers that included platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen, and D-dimer. FXIII levels were significantly lower in patients with liver or renal dysfunction. In conclusion, FXIII cross-linking activity measurements may have differential diagnostic value as well as predictive value in patients who are suspected to have DIC
Improved Adaptive Group Testing Algorithms with Applications to Multiple Access Channels and Dead Sensor Diagnosis
We study group-testing algorithms for resolving broadcast conflicts on a
multiple access channel (MAC) and for identifying the dead sensors in a mobile
ad hoc wireless network. In group-testing algorithms, we are asked to identify
all the defective items in a set of items when we can test arbitrary subsets of
items. In the standard group-testing problem, the result of a test is
binary--the tested subset either contains defective items or not. In the more
generalized versions we study in this paper, the result of each test is
non-binary. For example, it may indicate whether the number of defective items
contained in the tested subset is zero, one, or at least two. We give adaptive
algorithms that are provably more efficient than previous group testing
algorithms. We also show how our algorithms can be applied to solve conflict
resolution on a MAC and dead sensor diagnosis. Dead sensor diagnosis poses an
interesting challenge compared to MAC resolution, because dead sensors are not
locally detectable, nor are they themselves active participants.Comment: Expanded version of a paper appearing in ACM Symposium on Parallelism
in Algorithms and Architectures (SPAA), and preliminary version of paper
appearing in Journal of Combinatorial Optimizatio
Validation of a contemporary prostate cancer grading system using prostate cancer death as outcome
BACKGROUND: Gleason scoring (GS) has major deficiencies and a novel system of five grade groups (GSâ©œ6; 3+4; 4+3; 8; â©Ÿ9) has been recently agreed and included in the WHO 2016 classification. Although verified in radical prostatectomies using PSA relapse for outcome, it has not been validated using prostate cancer death as an outcome in biopsy series. There is debate whether an âoverall' or âworst' GS in biopsies series should be used. METHODS: Nine hundred and eighty-eight prostate cancer biopsy cases were identified between 1990 and 2003, and treated conservatively. Diagnosis and grade was assigned to each core as well as an overall grade. Follow-up for prostate cancer death was until 31 December 2012. A log-rank test assessed univariable differences between the five grade groups based on overall and worst grade seen, and using univariable and multivariable Cox proportional hazards. Regression was used to quantify differences in outcome. RESULTS: Using both âworst' and âoverall' GS yielded highly significant results on univariate and multivariate analysis with overall GS slightly but insignificantly outperforming worst GS. There was a strong correlation with the five grade groups and prostate cancer death. CONCLUSIONS: This is the largest conservatively treated prostate cancer cohort with long-term follow-up and contemporary assessment of grade. It validates the formation of five grade groups and suggests that the âworst' grade is a valid prognostic measure
The Generalized Gell-Mann--Low Theorem for Relativistic Bound States
The recently established generalized Gell-Mann--Low theorem is applied in
lowest perturbative order to bound-state calculations in a simple scalar field
theory with cubic couplings. The approach via the generalized Gell-Mann--Low
Theorem retains, while being fully relativistic, many of the desirable features
of the quantum mechanical approaches to bound states. In particular, no
abnormal or unphysical solutions are found in the model under consideration.
Both the non-relativistic and one-body limits are straightforward and
consistent. The results for the spectrum are compared to those of the
Bethe-Salpeter equation (in the ladder approximation) and related equations.Comment: 24 pages, 6 pspicture diagrams, 4 postscript figure
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