426 research outputs found
Neutropenic event risk and impaired chemotherapy delivery in six European audits of breast cancer treatment
Goals of work: The aims of this study were to assess chemotherapy treatment characteristics, neutropenic event (NE) occurrence and related risk factors in breast cancer patients in Western Europe. Materials and methods: Six retrospective audits of breast cancer chemotherapy were combined into a dataset of 2,860 individuals. NEs were defined as neutropenia-related hospitalisation, dose reduction ≥15% or dose delay ≥7days. Summation dose intensity (SDI) was calculated to compare different types of chemotherapy regimens on a single scale. Risk factors of NE occurrence and of low relative dose intensity (RDI) ≤85% were identified by multiple logistic regression. Main results: Patient populations were comparable between audits. Until 1998, cyclophosphamide, methotrexate and fluorouracil regimens were most frequently used, but thereafter, anthracycline-based regimens were most common. NEs occurred in 20% of the patients and low RDI in 16%. NE occurrence predicted low RDI and was associated with higher age, bigger body surface area, lower body mass index, regimen type, more chemotherapy cycles planned, normal to high SDI, concomitant radiotherapy and year of treatment. First cycle NE occurrence predicted NEs from cycle 2 onwards. A risk score using age, SDI, number of planned chemotherapy cycles and concomitant radiotherapy differentiated patients with increasing NE risk (9-37%). An alternative score version not using concomitant radiotherapy performed moderately less well. Conclusions: NEs occurred frequently in this combined dataset and they affected treatment delivery. Identifying patients at high NE risk enables targeted prophylaxis and may avoid dose limitation
Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions
Quantum criticality describes the collective fluctuations of matter
undergoing a second-order phase transition at zero temperature. It is being
discussed in a number of strongly correlated electron systems. A prototype case
occurs in the heavy fermion metals, in which antiferromagnetic quantum critical
points have been explicitly observed. Here, I address two types of
antiferromagnetic quantum critical points. In addition to the standard
description based on the fluctuations of the antiferromagnetic order, a local
quantum critical point is also considered. It contains inherently quantum modes
that are associated with a critical breakdown of the Kondo effect. Across such
a quantum critical point, there is a sudden collapse of a large Fermi surface
to a small one. I also consider the proximate antiferromagnetic and
paramagnetic phases, and these considerations lead to a global phase diagram.
Finally, I discuss the pertinent experiments on the antiferromagnetic heavy
fermions, briefly address the case of ferromagnetic heavy fermions, and outline
some directions for future studies.Comment: (v2) reference added, and typos corrected; (v1) 10 pages, 2 figures,
based on a plenary talk given at the International Conference on Quantum
Criticality and Novel Phases (QCNP09, Dresden
Extended M1 sum rule for excited symmetric and mixed-symmetry states in nuclei
A generalized M1 sum rule for orbital magnetic dipole strength from excited
symmetric states to mixed-symmetry states is considered within the
proton-neutron interacting boson model of even-even nuclei. Analytic
expressions for the dominant terms in the B(M1) transition rates from the first
and second states are derived in the U(5) and SO(6) dynamic symmetry
limits of the model, and the applicability of a sum rule approach is examined
at and in-between these limits. Lastly, the sum rule is applied to the new data
on mixed-symmetry states of 94Mo and a quadrupole d-boson ratio
is obtained in a largely
parameter-independent wayComment: 19 pages, 3 figures, Revte
Display of probability densities for data from a continuous distribution
Based on cumulative distribution functions, Fourier series expansion and
Kolmogorov tests, we present a simple method to display probability densities
for data drawn from a continuous distribution. It is often more efficient than
using histograms.Comment: 5 pages, 4 figures, presented at Computer Simulation Studies XXIV,
Athens, GA, 201
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
We have made the first measurements of the virtual Compton scattering (VCS)
process via the H exclusive reaction in the nucleon resonance
region, at backward angles. Results are presented for the -dependence at
fixed GeV, and for the -dependence at fixed near 1.5 GeV.
The VCS data show resonant structures in the first and second resonance
regions. The observed -dependence is smooth. The measured ratio of
H to H cross sections emphasizes the different
sensitivity of these two reactions to the various nucleon resonances. Finally,
when compared to Real Compton Scattering (RCS) at high energy and large angles,
our VCS data at the highest (1.8-1.9 GeV) show a striking -
independence, which may suggest a transition to a perturbative scattering
mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.
Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q^2=0.92 and 1.76 GeV^2
Virtual Compton Scattering (VCS) on the proton has been studied at Jefferson
Lab using the exclusive photon electroproduction reaction (e p --> e p gamma).
This paper gives a detailed account of the analysis which has led to the
determination of the structure functions P_LL-P_TT/epsilon and P_LT, and the
electric and magnetic generalized polarizabilities (GPs) alpha_E(Q^2) and
beta_M(Q^2) at values of the four-momentum transfer squared Q^2= 0.92 and 1.76
GeV^2. These data, together with the results of VCS experiments at lower
momenta, help building a coherent picture of the electric and magnetic GPs of
the proton over the full measured Q^2-range, and point to their non-trivial
behavior.Comment: version 2: modified according to PRC Editor's and Referee's
recommendations. Archival paper for the E93-050 experiment at JLab Hall A. 28
pages, 23 figures, 5 cross-section tables. To be submitted to Phys.Rev.
Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q**2 = 1.0 GeV**2
Exclusive electroproduction of pi0 mesons on protons in the backward
hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the
forward direction in coincidence with scattered electrons from the 4 GeV
electron beam in Jefferson Lab's Hall A. The data span the range of the total
(gamma* p) center-of-mass energy W from the pion production threshold to W =
2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and
sigma_TT were separated from the azimuthal distribution and are presented
together with the MAID and SAID parametrizations.Comment: 17 pages, 11 figures, information can be found at
http://hallaweb.jlab.org/experiment/E93-050/vcs.html updated content about
SAID analysis updated MAID results following new reference nucl-th/0310041
updated figure
The reaction dynamics of the 16O(e,e'p) cross section at high missing energies
We measured the cross section and response functions (R_L, R_T, and R_LT) for
the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 <=
E_miss <= 120 MeV at various missing momenta P_miss <= 340 MeV/c. For 25 <
E_miss < 50 MeV and P_miss \approx 60 MeV/c, the reaction is dominated by
single-nucleon knockout from the 1s1/2-state. At larger P_miss, the
single-particle aspects are increasingly masked by more complicated processes.
For E_miss > 60 MeV and P_miss > 200 MeV/c, the cross section is relatively
constant. Calculations which include contributions from pion exchange currents,
isobar currents and short-range correlations account for the shape and the
transversity but only for half of the magnitude of the measured cross section.Comment: 6 pages, 4 figures, submitted to Phys Rev Lett, formatting error
fixe
Large Momentum Transfer Measurements of the Deuteron Elastic Structure Function A(Q^2) at Jefferson Laboratory
The deuteron elastic structure function A(Q^2) has been extracted in the Q^2
range 0.7 to 6.0 (GeV/c)^2 from cross section measurements of elastic
electron-deuteron scattering in coincidence using the Hall A Facility of
Jefferson Laboratory. The data are compared to theoretical models based on the
impulse approximation with inclusion of meson-exchange currents, and to
predictions of quark dimensional scaling and perturbative quantum
chromodynamicsComment: Submitted to Physical Review Letter
Yersinia pestis Evolution on a Small Timescale: Comparison of Whole Genome Sequences from North America
Yersinia pestis, the etiologic agent of plague, was responsible for several devastating epidemics throughout history and is currently of global importance to current public heath and biodefense efforts. Y. pestis is widespread in the Western United States. Because Y. pestis was first introduced to this region just over 100 years ago, there has been little time for genetic diversity to accumulate. Recent studies based upon single nucleotide polymorphisms have begun to quantify the genetic diversity of Y. pestis in North America.To examine the evolution of Y. pestis in North America, a gapped genome sequence of CA88-4125 was generated. Sequence comparison with another North American Y. pestis strain, CO92, identified seven regions of difference (six inversions, one rearrangement), differing IS element copy numbers, and several SNPs.The relatively large number of inverted/rearranged segments suggests that North American Y. pestis strains may be undergoing inversion fixation at high rates over a short time span, contributing to higher-than-expected diversity in this region. These findings will hopefully encourage the scientific community to sequence additional Y. pestis strains from North America and abroad, leading to a greater understanding of the evolutionary history of this pathogen
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