1,368 research outputs found
Baryonic contributions to the dilepton spectrum of nucleon-nucleon collisions
We study the production of dileptons in relativistic nucleon-nucleon
collisions. Additionally to the traditional dilepton production channels
(vector meson decays, meson and Delta(1232) Dalitz decays) we included in our
model as new dilepton sources the Dalitz decay of higher unflavored baryon
resonances with spin<=5/2 and mass<=2.25 GeV/c^2. The contributions of these
new channels are estimated using experimental information about the Ngamma
decays of the resonances and have large uncertainties. The obtained dilepton
spectra are compared to the experimental data by the DLS collaboration.
Predictions for the HADES detector (SIS, GSI) are also discussed. In spite of
the large uncertainties of the higher resonance Dalitz decay contributions we
are able to draw the conclusion that these contributions are negligible
compared to the other dilepton sources and do not influence the detectability
of the phi and omega vector meson peaks.Comment: 9 pages, 4 figures, version accepted for publication in Phys. Rev.
I. Pasture and Forage Plants for South Dakota II. Feeding Dairy Cows III. Flies IV. The Artesian Waters of South Dakota V. Some Destructive Insects VI. Elements of Prairie Horticulture
I. Pastuire and Forage Plants for South Dakota II. Feeding Dairy Cows III. Flies IV. The Artesian Waters of South Dakota V. Some Destructive Insects VI. Elements of Prairie Horticultur
Angiogenesis in the synovium and at the osteochondral junction in osteoarthritis
SummaryObjectivesWe hypothesised that osteochondral and synovial angiogenesis in osteoarthritis (OA) are independent processes. We investigated whether indices of osteochondral and synovial angiogenesis display different relationships with synovitis, disease severity and chondrocalcinosis in patients with OA.DesignSynovium and medial tibial plateaux were obtained from 62 patients undergoing total knee joint replacement for OA (18 [29%] had chondrocalcinosis) and from 31 recently deceased people with no evidence of joint pathology post-mortem (PM). Vascular endothelium, proliferating endothelial cells (ECs) and macrophages were quantified by immunohistochemistry for CD34, CD31/Ki67 and CD14, respectively. Grades were assigned for radiographic and histological OA disease severity, clinical disease activity and histological synovitis (based on cellular content of the synovium).ResultsBlood vessels breached the tidemark in 60% of patients with OA and 20% of PM controls. Osteochondral vascular density increased with increasing cartilage severity and clinical disease activity scores, but not with synovitis. Synovial EC proliferation, inflammation and macrophage infiltration were higher in OA than in PM controls. Synovial angiogenesis indices increased with increasing histological synovitis, but were not related to osteochondral vascular density or other indices of OA disease severity. OA changes were more severe in patients with concurrent chondrocalcinosis. Chondrocalcinosis was not associated with increased angiogenesis or histological synovitis beyond that seen in OA alone.ConclusionOsteochondral and synovial angiogenesis appear to be independent processes. Osteochondral vascularity is associated with the severity of OA cartilage changes and clinical disease activity, whereas synovial angiogenesis is associated with histological synovitis. Modulation of osteochondral and synovial angiogenesis may differentially affect OA disease
Evaluating Process-Based Integrated Assessment Models of Climate Change Mitigation
Process-based integrated assessment models (IAMs) analyse transformation pathways to mitigate climate change. Confidence in models is established by testing their structural assumptions and comparing their behaviour against observations as well as other models. Climate model evaluation is concerted, and prominently reported in a dedicated chapter in the IPCC WG1 assessments. By comparison, evaluation of process-based IAMs tends to be less visible and more dispersed among modelling teams, with the exception of model inter-comparison projects. We contribute the first comprehensive analysis of process-based IAM evaluation, drawing on a wide range of examples across eight different evaluation methods testing both structural and behavioural validity. For each evaluation method, we compare its application to process-based IAMs with its application to climate models, noting similarities and differences, and seeking useful insights for strengthening the evaluation of process-based IAMs. We find that each evaluation method has distinctive strengths and limitations, as well as constraints on their application. We develop a systematic evaluation framework combining multiple methods that should be embedded within the development and use of process-based IAMs
Role of baryonic resonances in the dilepton emission in nucleon-nucleon collisions
Within an effective Lagrangian model, we present calculations for cross
sections of the dilepton production in proton-proton and proton-neutron
collisions at laboratory kinetic energies in 1-5 GeV range. Production
amplitudes include contributions from the nucleon-nucleon bremsstrahlung as
well as from the mechanism of excitation, propagation, and radiative decay of
Delta(1232) and N*(1520) intermediate baryonic resonances. It is found that the
delta isobar terms dominate the cross sections in the entire considered beam
energy range. Our calculations are able to explain the data of the DLS
collaboration on the dilepton production in proton-proton collisions for beam
energies below 1.3 GeV. However, for incident energies higher than this the
inclusion of contributions from other dilepton sources like Dalitz decay of pi0
and eta mesons, and direct decay of rho and omega mesons is necessary to
describe the data.Comment: 22 pages, 7 figures, more details of the calculations added, version
to appear in Phys. Rev
Renormalization of Hamiltonian Field Theory; a non-perturbative and non-unitarity approach
Renormalization of Hamiltonian field theory is usually a rather painful
algebraic or numerical exercise. By combining a method based on the coupled
cluster method, analysed in detail by Suzuki and Okamoto, with a Wilsonian
approach to renormalization, we show that a powerful and elegant method exist
to solve such problems. The method is in principle non-perturbative, and is not
necessarily unitary.Comment: 16 pages, version shortened and improved, references added. To appear
in JHE
Dilepton production in heavy ion collisions at intermediate energies
We present a unified description of the vector meson and dilepton production
in elementary and in heavy ion reactions. The production of vector mesons
() is described via the excitation of nuclear resonances ().
The theoretical framework is an extended vector meson dominance model (eVMD).
The treatment of the resonance decays with arbitrary spin is
covariant and kinematically complete. The eVMD includes thereby excited vector
meson states in the transition form factors. This ensures correct asymptotics
and provides a unified description of photonic and mesonic decays. The
resonance model is successfully applied to the production in
reactions. The same model is applied to the dilepton production in elementary
reactions (). Corresponding data are well reproduced. However, when
the model is applied to heavy ion reactions in the BEVALAC/SIS energy range the
experimental dilepton spectra measured by the DLS Collaboration are
significantly underestimated at small invariant masses. As a possible solution
of this problem the destruction of quantum interference in a dense medium is
discussed. A decoherent emission through vector mesons decays enhances the
corresponding dilepton yield in heavy ion reactions. In the vicinity of the
-peak the reproduction of the data requires further a substantial
collisional broadening of the and in particular of the meson.Comment: 32 pages revtex, 19 figures, to appear in PR
Investigation of a hydraulic impact: a technology in rock breaking
The finite element method and dimensional analysis have been applied in the
present paper to study a hydraulic impact, which is utilized in a non-explosive
rock breaking technology in mining industry. The impact process of a high speed
piston on liquid water, previously introduced in a borehole drilled in rock, is
numerically simulated. The research is focused on the influences of all the
parameters involved in the technology on the largest principal stress in the
rock, which is considered as one of the key factors to break the rock. Our
detailed parametric investigation reveals that the variation of the isotropic
rock material properties, especially its density, has no significant influence
on the largest principal stress. The influences of the depth of the hole and
the depth of the water column are also very small. On the other hand,
increasing the initial kinetic energy of the piston can dramatically increase
the largest principal stress and the best way to increase the initial kinetic
energy of the piston is to increase its initial velocity. Results from the
current dimensional analysis can be applied to optimize this non-explosive rock
breaking technology
The standing wave model of the mesons and baryons
Only photons are needed to explain the masses of the pi(0), eta, Lambda,
Sigma(0), Xi(0), Omega(-), Lambda(c,+), Sigma(c,0), Xi(c,0), and Omega(c,0)
mesons and baryons. Only neutrinos are needed to explain the mass of the pi(+-)
mesons. Neutrinos and photons are needed to explain the masses of the K-mesons,
the neutron and D-mesons. Surprisingly the mass of the mu-meson can also be
explained by the oscillation energies and rest masses of a neutrino lattice.
From the difference of the masses of the pi(+-) mesons and mu(+-) mesons
follows that the rest mass of the muon-neutrino is 47.5 milli-eV. From the
difference of the masses of the neutron and proton follows that the rest mass
of the electron-neutrino is 0.55 milli-eV. The potential of the weak force that
holds the lattices of the particles together can be determined with Born's
lattice theory. From the weak force follows automatically the existence of a
strong force between the sides of two lattices. The strong nuclear force is the
sum of the unsaturated weak forces at the sides of each lattice and is
therefore 10^6 times stronger than the weak force.Comment: 41 pages, 6 figure
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