16,005 research outputs found
Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model
We derive the effective potentials for composite operators in a
Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in
each case they are equivalent to the corresponding effective potentials based
on an auxiliary scalar field. The both effective potentials could lead to the
same possible spontaneous breaking and restoration of symmetries including
chiral symmetry if the momentum cutoff in the loop integrals is large enough,
and can be transformed to each other when the Schwinger-Dyson (SD) equation of
the dynamical fermion mass from the fermion-antifermion vacuum (or thermal)
condensates is used. The results also generally indicate that two effective
potentials with the same single order parameter but rather different
mathematical expressions can still be considered physically equivalent if the
SD equation corresponding to the extreme value conditions of the two potentials
have the same form.Comment: 7 pages, no figur
An in-host model of HIV incorporating latent infection and viral mutation
We construct a seven-component model of the in-host dynamics of the Human
Immunodeficiency Virus Type-1 (i.e, HIV) that accounts for latent infection and
the propensity of viral mutation. A dynamical analysis is conducted and a
theorem is presented which characterizes the long time behavior of the model.
Finally, we study the effects of an antiretroviral drug and treatment
implications.Comment: 10 pages, 7 figures, Proceedings of AIMS Conference on Differential
Equations and Dynamical Systems (2015
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The effect and stability of MVCT images on adaptive TomoTherapy.
Use of helical TomoTherapy-based MVCT imaging for adaptive planning is becoming increasingly popular. Treatment planning and dose calculations based on MVCT require an image value to electron density calibration to remain stable over the course of treatment time. In this work, we have studied the dosimetric impact on TomoTherapy treatment plans due to variation in image value to density table (IVDT) curve as a function of target degradation. We also have investigated the reproducibility and stability of the TomoTherapy MVCT image quality over time. Multiple scans of the TomoTherapy "Cheese" phantom were performed over a period of five months. Over this period, a difference of 4.7% in the HU values was observed in high-density regions while there was no significant variation in the image values for the low densities of the IVDT curve. Changes in the IVDT curves before and after target replacement were measured. Two clinical treatment sites, pelvis and prostate, were selected to study the dosimetric impact of this variation. Dose was recalculated on the MVCTs with the planned fluence using IVDT curves acquired before and after target change. For the cases studied, target replacement resulted in an overall difference of less than 5%, which can be significant for hypo-fractionated cases. Hence, it is recommended to measure the IVDT curves on a monthly basis and after any major repairs/replacements
Replica study of pinned bubble crystals
In higher Landau levels (), the ground state of the two-dimensional
electron gas in a strong perpendicular magnetic field evolves from a Wigner
crystal for small filling of the partially filled Landau level, into a
succession of bubble states with increasing number of guiding centers per
bubble as increases, to a modulated stripe state near . In
this work, we compute the frequency-dependent longitudinal conductivity of the Wigner and bubble crystal states in the presence
of disorder. We apply an elastic theory to the crystal states which is
characterized by a shear and a bulk modulus. We obtain both moduli from the
microscopic time-dependent Hartree-Fock approximation. We then use the replica
and Gaussian variational methods to handle the effects of disorder. Within the
semiclassical approximation we get the dynamical conductivity as well as the
pinning frequency as functions of the Landau level filling factor and compare
our results with recent microwave experiments.Comment: 19 pages and 6 eps figure
cDNA Cloning of the Basement Membrane Chondroitin Sulfate Proteoglycan Core Protein, Bamacan: A Five Domain Structure Including Coiled-Coil Motifs
Basement membranes contain several proteoglycans, and those bearing heparan sulfate glycosaminoglycans such as perlecan and agrin usually predominate. Most mammalian basement membranes also contain chondroitin sulfate, and a core protein, bamacan, has been partially characterized. We have now obtained cDNA clones encoding the entire bamacan core protein of Mr = 138 kD, which reveal a five domain, head-rod-tail configuration. The head and tail are potentially globular, while the central large rod probably forms coiled-coil structures, with one large central and several very short interruptions. This molecular architecture is novel for an extracellular matrix molecule, but it resembles that of a group of intracellular proteins, including some proposed to stabilize the mitotic chromosome scaffold. We have previously proposed a similar stabilizing role for bamacan in the basement membrane matrix. The protein sequence has low overall homology, apart from very small NH2- and COOH-terminal motifs
Energy Dependent Contrast in Atomic-Scale Spin-Polarized Scanning Tunneling Microscopy ofMn3N2(010): Experiment and First-Principles Theory
The technique of spin-polarized scanning tunneling microscopy is investigated
for its use in determining fine details of surface magnetic structure down to
the atomic scale. As a model sample, the row-wise anti-ferromagnetic Mn3N2(010)
surface is studied. It is shown that the magnetic contrast in atomic-scale
images is a strong function of the bias voltage around the Fermi level.
Inversion of the magnetic contrast is also demonstrated. The experimental
SP-STM images and height profiles are compared with simulated SP-STM images and
height profiles based on spin-polarized density functional theory. The success
of different tip models in reproducing the non-magnetic and magnetic STM data
is explored.Comment: 15 pages, 7 figure
Unified First Law and Thermodynamics of Apparent Horizon in FRW Universe
In this paper we revisit the relation between the Friedmann equations and the
first law of thermodynamics. We find that the unified first law firstly
proposed by Hayward to treat the "outer"trapping horizon of dynamical black
hole can be used to the apparent horizon (a kind of "inner" trapping horizon in
the context of the FRW cosmology) of the FRW universe. We discuss three kinds
of gravity theorties: Einstein theory, Lovelock thoery and scalar-tensor
theory. In Einstein theory, the first law of thermodynamics is always satisfied
on the apparent horizon. In Lovelock theory, treating the higher derivative
terms as an effective energy-momentum tensor, we find that this method can give
the same entropy formula for the apparent horizon as that of black hole
horizon. This implies that the Clausius relation holds for the Lovelock theory.
In scalar-tensor gravity, we find, by using the same procedure, the Clausius
relation no longer holds. This indicates that the apparent horizon of FRW
universe in the scalar-tensor gravity corresponds to a system of
non-equilibrium thermodynamics. We show this point by using the method
developed recently by Eling {\it et al.} for dealing with the gravity.Comment: v2: revtex, 23 pages, references added, minor changes, to appear in
PR
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