238 research outputs found
Mechanistic and pathological study of the genesis, growth, and rupture of abdominal aortic aneurysms
Postprint (published version
Update in Antiepidermal Growth Factor Receptor Therapy in the Management of Metastatic Colorectal Cancer
The approval of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies in the treatment of metastatic colorectal cancer (CRC) has expanded the armamentarium against this disease.
This paper will review the historical progress and recent clinical developments of anti-EGFR therapies in the treatment of metastatic CRC. Novel strategies of targeting the EGFR pathway to improve efficacy as well as ongoing research in identifying specific molecular predictors of response will be discussed
Magnetic Ground State of PrLaCeCuO with Varied Oxygen Depletion Probed by Muon Spin Relaxation
The magnetic ground state of an electron-doped cuprate superconductor
PrLaCeCuO () has been
studied by means of muon spin rotation/relaxation (\msr) over a wide variety of
oxygen depletion, . Appearance of weak random magnetism
over entire crystal volume has been revealed by a slow exponential relaxation.
The absence of -dependence for the random magnetism and the multiplet
pattern of muon Knight shift at higher fields strongly suggest that the random
moments are associated with excited Pr ions under crystal electric
field.Comment: 6 pages, 4 figures, submitted to J. Phys. Soc. Jp
Electron-phonon coupling induced pseudogap and the superconducting transition in Ba0.67K0.33BiO3
We study the single particle density of states (DOS) across the
superconducting transition (Tc = 31 K) in single-crystal Ba0.67K0.33BiO3 using
ultrahigh resolution angle-integrated photoemission spectroscopy. The
superconducting gap opens with a pile-up in the DOS, Delta(5.3 K) = 5.2 meV and
2Delta(0)/kBTc = 3.9. In addition, we observe a pseudogap below and above Tc,
occurring as a suppression in intensity over an energy scale up to the
breathing mode phonon(~ 70 meV). The results indicate electron-phonon coupling
induces a pseudogap in Ba0.67K0.33BiO3.Comment: 5 pages with 4 figures, submitted to Phys. Rev. Let
Heavy Fermion scaling: Uranium versus Cerium and Ytterbium compounds
In an effort to explore the differences between rare-earth-based and
uranium-based heavy Fermion (HF) compounds that reflect the underlying
difference between local 4 moments and itinerant 5 moments we analyze
scaling laws that relate the low temperature neutron spectra of the primary
("Kondo-esque") spin fluctuation to the specific heat and susceptibility. While
the scaling appears to work very well for the rare earth intermediate valence
compounds, for a number of key uranium compounds the scaling laws fail badly.
There are two main reasons for this failure. First, the presence of
antiferromagnetic (AF) fluctuations, which contribute significantly to the
specific heat, alters the scaling ratios. Second, the scaling laws require
knowledge of the high temperature moment degeneracy, which is often
undetermined for itinerant 5 electrons. By making plausible corrections for
both effects, better scaling ratios are obtained for some uranium compounds. We
point out that while both the uranium HF compounds and the rare earth
intermediate valence (IV) compounds have spin fluctuation characteristic
energies of order 5 - 25 meV, they differ in that the AF fluctuations that are
usually seen in the U compounds are never seen in the rare earth IV compounds.
This suggests that the 5f itineracy increases the f-f exchange relative to the
rare earth case
Linear Response Calculations of Spin Fluctuations
A variational formulation of the time--dependent linear response based on the
Sternheimer method is developed in order to make practical ab initio
calculations of dynamical spin susceptibilities of solids. Using gradient
density functional and a muffin-tin-orbital representation, the efficiency of
the approach is demonstrated by applications to selected magnetic and strongly
paramagnetic metals. The results are found to be consistent with experiment and
are compared with previous theoretical calculations.Comment: 11 pages, RevTex; 3 Figures, postscript, high-resolution printing
(~1200dpi) is desire
4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4)
We have performed inelastic magnetic neutron scattering experiments on
La(2-x-y)Sr(x)Nd(y)CuO(4) in order to study the Nd 4f-spin dynamics at low
energies. In all samples we find at high temperatures a quasielastic line
(Lorentzian) with a line width which decreases on lowering the temperature. The
temperature dependence of the quasielastic line width Gamma/2(T) can be
explained with an Orbach-process, i.e. a relaxation via the coupling between
crystal field excitations and phonons. At low temperatures the Nd-4f magnetic
response S(Q,omega) correlates with the electronic properties of the
CuO(2)-layers. In the insulator La(2-y)Nd(y)CuO(4) the quasielastic line
vanishes below 80 K and an inelastic excitation occurs. This directly indicates
the splitting of the Nd3+ ground state Kramers doublet due to the static
antiferromagnetic order of the Cu moments. In La(1.7-x)Sr(x)Nd(0.3)CuO(4) with
x = 0.12, 0.15 and La(1.4-x)Sr(x)Nd(0.6)CuO(4) with x = 0.1, 0.12, 0.15, 0.18
superconductivity is strongly suppressed. In these compounds we observe a
temperature independent broad quasielastic line of Gaussian shape below T about
30 K. This suggests a distribution of various internal fields on different Nd
sites and is interpreted in the frame of the stripe model. In
La(1.8-y)Sr(0.2)Nd(y)CuO(4) (y = 0.3, 0.6) such a quasielastic broadening is
not observed even at lowest temperature.Comment: 8 pages, 10 figures included, to appear in Phys. Rev.
Phase diagram of the one-dimensional extended attractive Hubbard model for large nearest-neighbor repulsion
We consider the extended Hubbard model with attractive on-site interaction U
and nearest-neighbor repulsions V. We construct an effective Hamiltonian
H_{eff} for hopping t<<V and arbitrary U<0. Retaining the most important terms,
H_{eff} can be mapped onto two XXZ models, solved by the Bethe ansatz. The
quantum phase diagram shows two Luttinger liquid phases and a region of phase
separation between them. For density n<0.422 and U<-4, singlet superconducting
correlations dominate at large distances. For some parameters, the results are
in qualitative agreement with experiments in BaKBiO.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
Neutron scattering study of Kondo lattice antiferromagnet YbNiSi3
The Kondo lattice antiferromagnet YbNiSi3 was investigated by neutron
scattering. The magnetic structure of YbNiSi3 was determined by neutron
diffraction on a single-crystalline sample. Inelastic scattering experiments
were also performed on a pulverized sample to study the crystalline electric
field (CEF) excitations. Two broad CEF excitations were observed, from which
the CEF parameters were determined. The temperature dependence of the magnetic
susceptibility chi and the magnetic specific heat Cmag were calculated using
the determined CEF model, and compared with previous results.Comment: 10 pages, 7 figures,submitted to JPS
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