2,192 research outputs found
Modeling the Effects of Multiple Myeloma on Kidney Function
Multiple myeloma (MM), a plasma cell cancer, is associated with many health
challenges, including damage to the kidney by tubulointerstitial fibrosis. We
develop a mathematical model which captures the qualitative behavior of the
cell and protein populations involved. Specifically, we model the interaction
between cells in the proximal tubule of the kidney, free light chains, renal
fibroblasts, and myeloma cells. We analyze the model for steady-state solutions
to find a mathematically and biologically relevant stable steady-state
solution. This foundational model provides a representation of dynamics between
key populations in tubulointerstitial fibrosis that demonstrates how these
populations interact to affect patient prognosis in patients with MM and renal
impairment.Comment: Included version of model without tumor with steady-state analysis,
corrected equations for free light chains and renal fibroblasts in model with
tumor to reflect steady-state analysis, updated abstract, updated and added
reference
The Role of Osteocytes in Targeted Bone Remodeling: A Mathematical Model
Until recently many studies of bone remodeling at the cellular level have
focused on the behavior of mature osteoblasts and osteoclasts, and their
respective precursor cells, with the role of osteocytes and bone lining cells
left largely unexplored. This is particularly true with respect to the
mathematical modeling of bone remodeling. However, there is increasing evidence
that osteocytes play important roles in the cycle of targeted bone remodeling,
in serving as a significant source of RANKL to support osteoclastogenesis, and
in secreting the bone formation inhibitor sclerostin. Moreover, there is also
increasing interest in sclerostin, an osteocyte-secreted bone formation
inhibitor, and its role in regulating local response to changes in the bone
microenvironment. Here we develop a cell population model of bone remodeling
that includes the role of osteocytes, sclerostin, and allows for the
possibility of RANKL expression by osteocyte cell populations. This model
extends and complements many of the existing mathematical models for bone
remodeling but can be used to explore aspects of the process of bone remodeling
that were previously beyond the scope of prior modeling work. Through numerical
simulations we demonstrate that our model can be used to theoretically explore
many of the most recent experimental results for bone remodeling, and can be
utilized to assess the effects of novel bone-targeting agents on the bone
remodeling process
Phase diagram of the one dimensional anisotropic Kondo-necklace model
The one dimensional anisotropic Kondo-necklace model has been studied by
several methods. It is shown that a mean field approach fails to gain the
correct phase diagram for the Ising type anisotropy. We then applied the spin
wave theory which is justified for the anisotropic case. We have derived the
phase diagram between the antiferromagnetic long range order and the Kondo
singlet phases. We have found that the exchange interaction (J) between the
itinerant spins and local ones enhances the quantum fluctuations around the
classical long range antiferromagnetic order and finally destroy the ordered
phase at the critical value, J_c. Moreover, our results show that the onset of
anisotropy in the XY term of the itinerant interactions develops the
antiferromagnetic order for J<J_c. This is in agreement with the qualitative
feature which we expect from the symmetry of the anisotropic XY interaction. We
have justified our results by the numerical Lanczos method where the structure
factor at the antiferromagnetic wave vector diverges as the size of system goes
to infinity.Comment: 9 pages and 9 eps figure
Polaron self-trapping in a honeycomb net
Small polaron behavior in a two dimensional honeycomb net is studied by
applying the strong coupling perturbative method to the Holstein molecular
crystal model. We find that small optical polarons can be mobile also if the
electrons are strongly coupled to the lattice. Before the polarons localize and
become very heavy, there is infact a window of {\it e-ph} couplings in which
the polarons are small and have masses of order times the bare
band mass according to the value of the adiabaticity parameter. The 2D
honeycomb net favors the mobility of small optical polarons in comparison with
the square lattice.Comment: 6 pages, 3 figures, to appear in J.Phys.:Condensed Matter {PACS:
63.10.+a, 63.20.Dj, 71.38.+i
An alternative approach for the dynamics of polarons in one dimension
We developed a new method based on functional integration to treat the
dynamics of polarons in one-dimensional systems. We treat the acoustical and
the optical case in an unified manner, showing their differences and
similarities. The mobility and diffusion coefficients are calculated in the
Markovian approximation in the strong coupling limit.Comment: 57 page
Giant enhancement of anisotropy by electron-phonon interaction
Anisotropic electron-phonon interaction is shown to lead to the anisotropic
polaron effect. The resulting anisotropy of the polaron band is an exponential
function of the electron-phonon coupling and might be as big as . This
also makes anisotropy very sensitive to small changes of coupling and implies
wide variations of anisotropy among compounds of similar structure. The isotope
effect on mass anisotropy is predicted. Polaron masses are obtained by an exact
Quantum Monte Carlo method. Implications for high-temperature superconductors
are briefly discussed.Comment: 5 pages, 4 figure
Pion and Kaon Polarizabilities and Radiative Transitions
CERN COMPASS plans measurements of gamma-pi and gamma-K interactions using
50-280 GeV pion (kaon) beams and a virtual photon target. Pion (kaon)
polarizabilities and radiative transitions will be measured via Primakoff
effect reactions such as pi+gamma->pi'+gamma and pi+gamma->meson. The former
can test a precise prediction of chiral symmetry; the latter for
pi+gamma->a1(1260) is important for understanding the polarizability. The
radiative transition of a pion to a low mass two-pion system, pi+gamma->pi+pi0,
can also be studied to measure the chiral anomaly amplitude F(3pi)
(characterizing gamma->3pi), arising from the effective Chiral Lagrangian. We
review here the motivation for the above physics program. We describe the beam,
target, detector, and trigger requirements for these experiments. We also
describe FNAL SELEX attempts to study related physics via the interaction of
600 GeV pions with target electrons. Data analysis in progress aims to identify
the reactions pi+e->pi'+e'+pi0 related to the chiral anomaly, and
pi+e->pi'+e'+gamma related to pion polarizabilities.Comment: 16 pages, 6 figures, Latex Springer-Verlag style Tel Aviv U. Preprint
TAUP-2469-97, Contribution to the Workshop on Chiral Dynamics Theory and
Experiment, U. of Mainz, Sept. 1-5, 1997, to be published in Springer-Verlag,
Eds. A. Bernstein, Th. Walcher, 199
- …