323 research outputs found
Optimizing XML Compression
The eXtensible Markup Language (XML) provides a powerful and flexible means
of encoding and exchanging data. As it turns out, its main advantage as an
encoding format (namely, its requirement that all open and close markup tags
are present and properly balanced) yield also one of its main disadvantages:
verbosity. XML-conscious compression techniques seek to overcome this drawback.
Many of these techniques first separate XML structure from the document
content, and then compress each independently. Further compression gains can be
realized by identifying and compressing together document content that is
highly similar, thereby amortizing the storage costs of auxiliary information
required by the chosen compression algorithm. Additionally, the proper choice
of compression algorithm is an important factor not only for the achievable
compression gain, but also for access performance. Hence, choosing a
compression configuration that optimizes compression gain requires one to
determine (1) a partitioning strategy for document content, and (2) the best
available compression algorithm to apply to each set within this partition. In
this paper, we show that finding an optimal compression configuration with
respect to compression gain is an NP-hard optimization problem. This problem
remains intractable even if one considers a single compression algorithm for
all content. We also describe an approximation algorithm for selecting a
partitioning strategy for document content based on the branch-and-bound
paradigm.Comment: 16 pages, extended version of paper accepted for XSym 200
Nucleon-deuteron scattering with the JISP16 potential
The nucleon-nucleon J-matrix Inverse Scattering Potential JISP16 is applied
to elastic nucleon-deuteron (Nd) scattering and the deuteron breakup process at
the lab. nucleon energies up to 135 MeV. The formalism of the Faddeev equations
is used to obtain 3N scattering states. We compare predictions based on the
JISP16 force with data and with results based on various NN interactions: the
CD Bonn, the AV18, the chiral force with the semi-local regularization at the
5th order of the chiral expansion and with low-momentum interactions obtained
from the CD Bonn force as well as with the predictions from the combination of
the AV18 NN interaction and the Urbana IX 3N force. JISP16 provides a
satisfactory description of some observables at low energies but strong
deviations from data as well as from standard and chiral potential predictions
with increasing energy. However, there are also polarization observables at low
energies for which the JISP16 predictions differ from those based on the other
forces by a factor of two. The reason for such a behavior can be traced back to
the P-wave components of the JISP16 force. At higher energies the deviations
can be enhanced by an interference with higher partial waves and by the
properties of the JISP16 deuteron wave function. In addition, we compare the
energy and angular dependence of predictions based on the JISP16 force with the
results of the low-momentum forces obtained with different values of the
momentum cutoff parameter. We found that such low-momentum forces can be
employed to interpret the Nd elastic scattering data only below some specific
energy which depends on the cutoff parameter. Since JISP16 is defined in a
finite oscillator basis, it has properties similar to low momentum interactions
and its application to the description of Nd scattering data is limited to a
low momentum transfer region.Comment: 26 pages, 12 eps figures; Version accepted to Phys. Rev. C: text is
shortened, few figures regarding the nucleon-deuteron elastic scattering
observables are removed but a short discussion of the nucleon induced
deuteron breakup cross section is added. Conclusions remain unchange
Faddeev calculations of break-up reactions with realistic experimental constraints
We present a method to integrate predictions from a theoretical model of a
reaction with three bodies in the final state over the region of phase space
covered by a given experiment. The method takes into account the true
experimental acceptance, as well as variations of detector efficiency, and
eliminates the need for a Monte-Carlo simulation of the detector setup. The
method is applicable to kinematically complete experiments. Examples for the
use of this method include several polarization observables in dp break-up at
270 MeV. The calculations are carried out in the Faddeev framework with the CD
Bonn nucleon-nucleon interaction, with or without the inclusion of an
additional three-nucleon force.Comment: 18 pages, 9 figure
Comprehensive investigation of the symmetric space-star configuration in the nucleon-deuteron breakup
We examine a description of available cross section data for symmetric space
star (SST) configurations in the neutron-deuteron (nd) and proton-deuteron (pd)
breakup reaction using numerically exact solutions of the three-nucleon (3N)
Faddeev equation based on two- and three-nucleon (semi)phenomenological and
chiral forces. The predicted SST cross sections are very stable with respect to
the underlying dynamics for incoming nucleon laboratory energies below MeV. We discuss possible origins of the surprising discrepancies between
theory and data found in low-energy nd and pd SST breakup measurements.Comment: 30 pages, 12 figure
Experimental search for evidence of the three-nucleon force and a new analysis method
A research program with the aim of investigating the spin dependence of the
three-nucleon continuum in pd collisions at intermediate energies was carried
out at IUCF using the Polarized INternal Target EXperiments (PINTEX) facility.
In the elastic scattering experiment at 135 and 200 MeV proton beam energies a
total of 15 independent spin observables were obtained. The breakup experiment
was done with a vector and tensor polarized deuteron beam of 270 MeV and an
internal polarized hydrogen gas target. We developed a novel technique for the
analysis of the breakup observables, the sampling method. The new approach
takes into account acceptance and non-uniformities of detection efficiencies
and is suitable for any kinematically complete experiment with three particles
in the final state.Comment: Contribution to the 19th European Few-Body Conference, Groningen Aug.
23-27, 200
Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces
We apply improved nucleon-nucleon potentials up to fifth order in chiral
effective field theory, along with a new analysis of the theoretical truncation
errors, to study nucleon-deuteron (Nd) scattering and selected low-energy
observables in 3H, 4He, and 6Li. Calculations beyond second order differ from
experiment well outside the range of quantified uncertainties, providing truly
unambiguous evidence for missing three-nucleon forces within the employed
framework. The sizes of the required three-nucleon force contributions agree
well with expectations based on Weinberg's power counting. We identify the
energy range in elastic Nd scattering best suited to study three-nucleon force
effects and estimate the achievable accuracy of theoretical predictions for
various observables.Comment: 5 pages, 5 figure
Low-energy neutron-deuteron reactions with N3LO chiral forces
We solve three-nucleon Faddeev equations with nucleon-nucleon and
three-nucleon forces derived consistently in the framework of chiral
perturbation theory at next-to-next-to-next-to-leading order in the chiral
expansion. In this first investigation we include only matrix elements of the
three-nucleon force for partial waves with the total two-nucleon
(three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron
elastic scattering and deuteron breakup reaction are studied. Emphasis is put
on Ay puzzle in elastic scattering and cross sections in symmetric-space-star
and neutron-neutron quasi-free-scattering breakup configurations, for which
large discrepancies between data and theory have been reported.Comment: 22 pages, 7 figure
Dependence of the C(,pd) reaction on photon linear polarisation
The sensitivity of the C reaction to photon linear
polarisation has been determined at MAMI, giving the first measurement of the
reaction for a nucleus heavier than He. Photon asymmetries and cross
sections were measured for =170 to 350 MeV. For below
the resonance, reactions leaving the residual Be near its ground
state show a positive asymmetry of up to 0.3, similar to that observed for
He suggesting a similar reaction mechanism for the two nuclei.Comment: 4 pages, 2 figure
Spin observables in deuteron-proton radiative capture at intermediate energies
A radiative deuteron-proton capture experiment was carried out at KVI using
polarized-deuteron beams at incident energies of 55, 66.5, and 90 MeV/nucleon.
Vector and tensor-analyzing powers were obtained for a large angular range. The
results are interpreted with the help of Faddeev calculations, which are based
on modern two- and three-nucleon potentials. Our data are described well by the
calculations, and disagree significantly with the observed tensor anomaly at
RCNP.Comment: 10 pages, 4 figures, submitted to PL
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Anatomical localization of progenitor cells in human breast tissue reveals enrichment of uncommitted cells within immature lobules
Introduction: Lineage tracing studies in mice have revealed the localization and existence of lineage-restricted mammary epithelial progenitor cells that functionally contribute to expansive growth during puberty and differentiation during pregnancy. However, extensive anatomical differences between mouse and human mammary tissues preclude the direct translation of rodent findings to the human breast. Therefore, here we characterize the mammary progenitor cell hierarchy and identify the anatomic location of progenitor cells within human breast tissues. Methods: Mammary epithelial cells (MECs) were isolated from disease-free reduction mammoplasty tissues and assayed for stem/progenitor activity in vitro and in vivo. MECs were sorted and evaluated for growth on collagen and expression of lineages markers. Breast lobules were microdissected and individually characterized based on lineage markers and steroid receptor expression to identify the anatomic location of progenitor cells. Spanning-tree progression analysis of density-normalized events (SPADE) was used to identify the cellular hierarchy of MECs within lobules from high-dimensional cytometry data. Results: Integrating multiple assays for progenitor activity, we identified the presence of luminal alveolar and basal ductal progenitors. Further, we show that Type I lobules of the human breast were the least mature, demonstrating an unrestricted pattern of expression of luminal and basal lineage markers. Consistent with this, SPADE analysis revealed that immature lobules were enriched for basal progenitor cells, while mature lobules consisted of increased hierarchal complexity of cells within the luminal lineages. Conclusions: These results reveal underlying differences in the human breast epithelial hierarchy and suggest that with increasing glandular maturity, the epithelial hierarchy also becomes more complex. Electronic supplementary material The online version of this article (doi:10.1186/s13058-014-0453-3) contains supplementary material, which is available to authorized users
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