35 research outputs found
Radiative corrections to the charged pion-pair production process {\boldmath} at low energies
We calculate the one-photon loop radiative corrections to the charged
pion-pair production process . In the low-energy
region this reaction is governed by the chiral pion-pion interaction. The
pertinent set of 42 irreducible photon-loop diagrams is calculated by using the
package FeynCalc. Electromagnetic counterterms with two independent low-energy
constants and are included in order to remove the
ultraviolet divergences generated by the photon-loops. Infrared finiteness of
the virtual radiative corrections is achieved by including soft photon
radiation below an energy cut-off . The purely electromagnetic
interaction of the charged pions mediated by one-photon exchange is also taken
into account. The radiative corrections to the total cross section (in the
isospin limit) vary between close to threshold and about at a
center-of-mass energy of . The largest contribution comes from the
simple one-photon exchange. Radiative corrections to the and
mass spectra are studied as well. The Coulomb singularity of the
final-state interaction produces a kink in the dipion mass spectra. The virtual
radiative corrections to elastic scattering are derived
additionally.Comment: 19 pages, 17 figures, accepted for publication in Eur. Phys. J.
Strangeness S=-2 baryon-baryon interaction at next-to-leading order in chiral effective field theory
The strangeness baryon-baryon interaction is studied in chiral
effective field theory up to next-to-leading order. The potential at this order
consists of contributions from one- and two-pseudoscalar-meson exchange
diagrams and from four-baryon contact terms without and with two derivatives.
SU(3) flavor symmetry is imposed for constructing the interaction in the
sector. Specifically, the couplings of the pseudoscalar mesons to the baryons
are fixed by SU(3) symmetry and, in general, also the contact terms are related
via SU(3) symmetry to those determined in a previous study of the
hyperon-nucleon interaction. The explicit SU(3) symmetry breaking due to the
physical masses of the pseudoscalar mesons (, , ) is taken into
account. It is argued that the interaction has to be relatively weak to
be in accordance with available experimental constraints. In particular, the
published values and upper bounds for the elastic and inelastic cross
sections apparently rule out a somewhat stronger attractive force and,
specifically, disfavor any near-threshold deuteron-like bound states in that
system.Comment: 17 pages, 7 figure
Scattering of decuplet baryons in chiral effective field theory
A formalism for treating the scattering of decuplet baryons in chiral
effective field theory is developed. The minimal Lagrangian and potentials in
leading-order SU(3) chiral effective field theory for the interactions of octet
baryons () and decuplet baryons () for the transitions ,
, , , , and are provided. As an application of the formalism we compare
with results from lattice QCD simulations for and
scattering. Implications of our results pertinent to the quest for dibaryons
are discussed.Comment: 26 pages, 6 figures; minor corrections in the text, references adde
Hyperons in nuclear matter from SU(3) chiral effective field theory
Brueckner theory is used to investigate the properties of hyperons in nuclear
matter. The hyperon-nucleon interaction is taken from chiral effective field
theory at next-to-leading order with SU(3) symmetric low-energy constants.
Furthermore, the underlying nucleon-nucleon interaction is also derived within
chiral effective field theory. We present the single-particle potentials of
Lambda and Sigma hyperons in symmetric and asymmetric nuclear matter computed
with the continuous choice for intermediate spectra. The results are in good
agreement with the empirical information. In particular, our calculation gives
a repulsive Sigma-nuclear potential and a weak Lambda-nuclear spin-orbit force.Comment: 13 pages, 10 figures, 5 tables; v2: published version, minor change
Do bound states exist?
The existence of baryon-baryon bound states in the strangeness sector is
examined in the framework of SU(3) chiral effective field theory. Specifically,
the role of SU(3) symmetry breaking contact terms that arise at next-to-leading
order in the employed Weinberg power counting scheme is explored. We focus on
the 1S0 partial wave and on baryon-baryon channels with maximal isospin since
in this case there are only two independent SU(3) symmetry breaking contact
terms. At the same time, those are the channels where most of the bound states
have been predicted in the past. Utilizing phase shifts and
cross section data allows us to pin down one of the SU(3) symmetry breaking
contact terms and a clear indication for the decrease of attraction when going
from the NN system to strangeness S=-2 is found, which rules out a bound state
for with isospin I=2. Assuming that the trend observed for S=0
to S=-2 is not reversed when going to and makes also bound
states in those systems rather unlikely.Comment: 10 pages, 4 figure
Hyperon-nucleon interaction at next-to-leading order in chiral effective field theory
Results for the Lambda N and Sigma N interactions obtained at next-to-leading
order in chiral effective field theory are reported. At the order considered
there are contributions from one- and two-pseudoscalar-meson exchange diagrams
and from four-baryon contact terms without and with two derivatives. SU(3)
flavor symmetry is imposed for constructing the hyperon-nucleon interaction
while the explicit SU(3) symmetry breaking by the physical masses of the
pseudoscalar mesons (pi, K, eta) is taken into account. An excellent
description of the hyperon-nucleon system can be achieved at next-to-leading
order. It is on the same level of quality as the one obtained by the most
advanced phenomenological hyperon-nucleon interaction models.Comment: 29 pages, 14 figures, uses elsarticle.cls and elsart3p.cl
The effects of nanoparticle drug loading on the pharmacokinetics of anticancer agents
Major advances in carrier-mediated agents, which include nanoparticles, nanosomes and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages, such as greater solubility, duration of exposure and delivery to the site of action over their small-molecule counterparts, there is substantial variability in systemic clearance and distribution, tumor delivery and pharmacologic effects (efficacy and toxicity) of these agents. This review provides an overview of factors that affect the pharmacokinetics and pharmacodynamics of carrier-mediated agents in preclinical models and patients
Effect of exercise on the caloric intake of breast cancer patients undergoing treatment
The purpose of this study was to examine the effects of an exercise intervention on the total caloric intake (TCI) of breast cancer patients undergoing treatment. A secondary purpose was to determine whether or not a relationship existed between changes in TCI, body fat composition (%BF), and fatigue during the study, which lasted 6 months. Twenty females recently diagnosed with breast cancer, scheduled to undergo chemotherapy or radiation, were assigned randomly to an experimental (N = 10) or control group (N = 10). Outcome measures included TCI (3-day food diary), %BF (skinfolds), and fatigue (revised Piper Fatigue Scale). Each exercise session was conducted as follows: initial cardiovascular activity (6-12 min), followed by stretching (5-10 min), resistance training (15-30 min), and a cool-down (approximately 8 min). Significant changes in TCI were observed among groups (F1,18 = 8.582; P = 0.009), at treatments 2 and 3, and at the end of the study [experimental (1973 ± 419), control (1488 ± 418); experimental (1946 ± 437), control (1436 ± 429); experimental (2315 ± 455), control (1474 ± 294), respectively]. A significant negative correlation was found (Spearman rho(18) = -0.759; P < 0.001) between TCI and %BF and between TCI and fatigue levels (Spearman rho(18) = -0.541; P = 0.014) at the end of the study. In conclusion, the results of this study suggest that an exercise intervention administered to breast cancer patients undergoing medical treatment may assist in the mitigation of some treatment side effects, including decreased TCI, increased fatigue, and negative changes in body composition
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe