293 research outputs found
A single administration of combination therapy inhibits breast tumour progression in bone and modifies both osteoblasts and osteoclasts
We have previously shown that repeated sequential administration of doxorubicin, followed 24 h later by zoledronic acid, inhibits tumour growth in models of established breast cancer bone metastasis. As breast cancer patients only receive zoledronic acid every 3-4 weeks, the aim of the current study was to establish the anti-tumour and bone effects of a single administration of doxorubicin/zoledronic acid combination therapy in a bone metastasis model. MDA-MB-231-GFP cells were injected i.c. in 6-week-old nude mice. On day 2, animals received PBS, doxorubicin (2 mg/kg i.v.), zoledronic acid (100 μg/kg s.c.) or doxorubicin followed 24 h later by zoledronic acid. Anti-tumour effects were assessed on days 15/23 by quantification of apoptotic and proliferating cells and changes in expression of genes implicated in apoptosis, proliferation and bone turnover. Bone effects were assessed by μCT analysis, bone histomorphometry and measurement of serum markers. A tumour-free control group was included. Combination treatment reduced bone tumour burden compared to single agent or PBS control and increased levels of tumour cell apoptosis on day 15, but this was no longer detectable on day 23. Animals receiving zoledronic acid had increased bone density, without evidence of tumour-induced lesions. Bone histomorphometry showed that zoledronic acid caused a decrease in osteoblast and osteoclast numbers and an increase in osteoclast size, in both tumour-free and tumour-bearing animals. Our data show that although zoledronic acid modifies the bone microenvironment through effects on both osteoblasts and osteoclasts, this does not result in a significant anti-tumour effect in the absence of doxorubicin. © 2012 Elsevier GmbH. All rights reserved
Superconductivity in the SU(N) Anderson Lattice at U=\infty
We present a mean-field study of superconductivity in a generalized N-channel
cubic Anderson lattice at U=\infty taking into account the effect of a
nearest-neighbor attraction J. The condition U=\infty is implemented within the
slave-boson formalism considering the slave bosons to be condensed. We consider
the -level occupancy ranging from the mixed valence regime to the Kondo
limit and study the dependence of the critical temperature on the various model
parameters for each of three possible Cooper pairing symmetries (extended s,
d-wave and p-wave pairing) and find interesting crossovers. It is found that
the d- and p- wave order parameters have, in general, very similar critical
temperatures. The extended s-wave pairing seems to be relatively more stable
for electronic densities per channel close to one and for large values of the
superconducting interaction J.Comment: Seven Figures; one appendix. Accepted for publication in Phys. Rev.
Multi-Channel Kondo Necklace
A multi--channel generalization of Doniach's Kondo necklace model is
formulated, and its phase diagram studied in the mean--field approximation. Our
intention is to introduce the possible simplest model which displays some of
the features expected from the overscreened Kondo lattice. The conduction
electron channels are represented by sets of pseudospins \vt_{j}, , which are all antiferromagnetically coupled to a periodic array of
|\vs|=1/2 spins. Exploiting permutation symmetry in the channel index
allows us to write down the self--consistency equation for general . For
, we find that the critical temperature is rising with increasing Kondo
interaction; we interpret this effect by pointing out that the Kondo coupling
creates the composite pseudospin objects which undergo an ordering transition.
The relevance of our findings to the underlying fermionic multi--channel
problem is discussed.Comment: 29 pages (2 figures upon request from [email protected]), LATEX,
submitted for publicatio
Categorizing Different Approaches to the Cosmological Constant Problem
We have found that proposals addressing the old cosmological constant problem
come in various categories. The aim of this paper is to identify as many
different, credible mechanisms as possible and to provide them with a code for
future reference. We find that they all can be classified into five different
schemes of which we indicate the advantages and drawbacks.
Besides, we add a new approach based on a symmetry principle mapping real to
imaginary spacetime.Comment: updated version, accepted for publicatio
Jorge A. Swieca's contributions to quantum field theory in the 60s and 70s and their relevance in present research
After revisiting some high points of particle physics and QFT of the two
decades from 1960 to 1980, I comment on the work by Jorge Andre Swieca. I
explain how it fits into the quantum field theory during these two decades and
draw attention to its relevance to the ongoing particle physics research. A
particular aim of this article is to direct thr readers mindfulness to the
relevance of what at the time of Swieca was called "the Schwinger Higgs
screening mechanism". which, together with recent ideas which generalize the
concept of gauge theories, has all the ingredients to revolutionize the issue
of gauge theories and the standard model.Comment: 49 pages, expansion and actualization of text, improvement of
formulations and addition of many references to be published in EPJH -
Historical Perspectives on Contemporary Physic
A Survey of Volunteered Open Geo-Knowledge Bases in the Semantic Web
Over the past decade, rapid advances in web technologies, coupled with
innovative models of spatial data collection and consumption, have generated a
robust growth in geo-referenced information, resulting in spatial information
overload. Increasing 'geographic intelligence' in traditional text-based
information retrieval has become a prominent approach to respond to this issue
and to fulfill users' spatial information needs. Numerous efforts in the
Semantic Geospatial Web, Volunteered Geographic Information (VGI), and the
Linking Open Data initiative have converged in a constellation of open
knowledge bases, freely available online. In this article, we survey these open
knowledge bases, focusing on their geospatial dimension. Particular attention
is devoted to the crucial issue of the quality of geo-knowledge bases, as well
as of crowdsourced data. A new knowledge base, the OpenStreetMap Semantic
Network, is outlined as our contribution to this area. Research directions in
information integration and Geographic Information Retrieval (GIR) are then
reviewed, with a critical discussion of their current limitations and future
prospects
Observation of exclusive DVCS in polarized electron beam asymmetry measurements
We report the first results of the beam spin asymmetry measured in the
reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry
with a sin(phi) modulation is observed, as predicted for the interference term
of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The
amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and
leading-twist pQCD, the alpha is directly proportional to the imaginary part of
the DVCS amplitude.Comment: 6 pages, 5 figure
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV
Differential cross sections for the reaction gamma p -> eta-prime p have been
measured with the CLAS spectrometer and a tagged photon beam with energies from
1.527 to 2.227 GeV. The results reported here possess much greater accuracy
than previous measurements. Analyses of these data indicate for the first time
the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710)
resonances, known to couple strongly to the eta N channel in photoproduction on
the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure
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