840 research outputs found
Preliminary results of fast neutron treatments in carcinoma of the pancreas
A group of 30 patients with adenocarcinoma of the pancreas including some patients with very advanced disease, were treated with the so-called mixed beam modality employing photon treatments three times per week and neutron treatments twice a week. Two hundred Rads or equivalent Rads (RBE 3.3) were given in daily fractions aiming at a total dose of 6000 Rads in 6 to 8 weeks. The treatments were well tolerated and significant palliation was achieved in 26 to 30 cases. Twelve months survival was 33 percent with a median survival of 7 months or 210 days. Treatment techniques and localization procedures are discussed
Field Dependent Superfluid Density in the Optimally Doped SmFeAsO_(1-x)F_y Superconductor
The magnetic field dependence of the in-plane magnetic penetration depth for
optimally doped SmFeAsO_(1-x)F_y was investigated by combining torque
magnetometry, SQUID magnetometry, and muon-spin rotation. The results obtained
from these techniques show all a pronounced decrease of the superfluid density
as the field is increased up to 1.4 T. This behavior is analysed within a
two-band model with self-consistently derived coupled gaps, where the
superfluid density related to the larger gap is field independent and the
superfluid density related to the smaller gap is strongly suppressed with
increasing field.Comment: 7 pages, 5 figure
Strong coupling between Eu2+ spins and Fe2As2 layers in EuFe1.9Co0.1As2 observed with NMR
A combination of x-ray diffraction, magnetization, and 75As nuclear magnetic
resonance (NMR) experiments were performed on single-crystal EuFe1.9Co0.1As2.
The strength of the hyperfine interaction between the 75As nuclei and the
Eu^(2+) 4f states suggests a strong coupling between the Eu^(2+) moments and
the Fe1.9Co0.1As2 layers. Such a strong interlayer coupling may be due to an
indirect exchange interaction between the localized Eu^(2+) 4f moments,
mediated by the Fe 3d conduction electrons. Magnetic susceptibility as well as
75As-NMR measurements reveal a decrease of the SDW transition temperature to
T_SDW = 120 K as a result of Co doping. A change of the slope in the
temperature dependence of the NMR frequency of the 75As lower-satellite line
was observed at 225 K. At the same temperature also a change of the satellite
line shape was found. These changes of the NMR spectra may be caused by the
formation of a nematic phase below 225 K in EuFe1.9Co0.1As2.Comment: 8 pages, 7 figure
{Rearrangement of the antiferromagnetic ordering at high magnetic fields in SmFeAsO and SmFeAsOF single crystals
The low-temperature antiferromagnetic state of the Sm-ions in both
nonsuperconducting SmFeAsO and superconducting SmFeAsOF single
crystals was studied by magnetic torque, magnetization, and magnetoresistance
measurements in magnetic fields up to 60~T and temperatures down to 0.6~K. We
uncover in both compounds a distinct rearrangement of the antiferromagnetically
ordered Sm-moments near ~T. This is seen in both, static and pulsed
magnetic fields, as a sharp change in the sign of the magnetic torque, which is
sensitive to the magnetic anisotropy and hence to the magnetic moment in the
-plane, ({\it i.e.} the FeAs-layers), and as a jump in the magnetization
for magnetic fields perpendicular to the conducting planes. This rearrangement
of magnetic ordering in ~T is essentially temperature independent and
points towards a canted or a partially polarized magnetic state in high
magnetic fields. However, the observed value for the saturation moment above
this rearrangement, suggests that the complete suppression of the
antiferromagnetism related to the Sm-moments would require fields in excess of
60~T. Such a large field value is particularly remarkable when compared to the
relatively small N\'{e}el temperature ~K, suggesting very
anisotropic magnetic exchange couplings. At the transition, magnetoresistivity
measurements show a crossover from positive to negative field-dependence,
indicating that the charge carriers in the FeAs planes are sensitive to the
magnetic configuration of the rare-earth elements. This is indicates a finite
magnetic/electronic coupling between the SmO and the FeAs layers which are
likely to mediate the exchange interactions leading to the long range
antiferromagnetic order of the Sm ions.Comment: 10 pages, 7 figures, accepted in Phys. Rev.
Interferon enhances the susceptibility of virus-infected fibroblasts to cytotoxic T cells.
Cities in fiction: Perambulations with John Berger
This paper explores selected novels by John Berger in which cities play a central role. These cities are places, partially real and partially imagined, where memory, hope, and despair intersect. My reading of the novels enables me to trace important themes in recent discourses on the nature of contemporary capitalism, including notions of resistance and universality. I also show how Berger?s work points to a writing that can break free from the curious capacity of capitalism to absorb and feed of its critique
Evidence for two distinct anisotropies in the oxypnictide superconductors SmFeAsO_(0.8)F_(0.2) and NdFeAsO_(0.8)F_(0.2)
Single crystals of the oxypnictide superconductors SmFeAsO_(0.8)F_(0.2) and
NdFeAsO_(0.8)F_(0.2) with T_c in the range of 44 K to 48 K were investigated by
torque magnetometry. An analysis of the data in terms of a recently proposed
model for the anisotropic magnetization in the superconducting state, treating
the penetration depth anisotropy differently than the upper critical field
anisotropy, provides evidence that in the oxypnictide superconductors two
distinct anisotropies are present. As a result the penetration depth anisotropy
differs significantly in magnitude and in temperature dependence from the upper
critical field anisotropy, analogous to MgB_2 but with a reversed sign of
slope. This scenario strongly suggests a new multi-band mechanism in the novel
class of oxypnictide high-temperature superconductors.Comment: published online in J. Supercond. Nov. Mag
First-Principles Study for the Anisotropy of Iron-based Superconductors toward Power and Device Applications
Performing the first-principles calculations, we investigate the anisotropy
in the superconducting state of iron-based superconductors to gain an insight
into their potential applications. The anisotropy ratio of the
c-axis penetration depth to the ab-plane one is relatively small in BaFe2As2
and LiFeAs, i.e., , indicating that the transport
applications are promising in these superconductors. On the other hand, in
those having perovskite type blocking layers such as Sr2ScFePO3 we find a very
large value, , comparable to that in strongly
anisotropic high-Tc cuprate Bi2Sr2CaCu2O{8-\delta}. Thus, the intrinsic
Josephson junction stacks are expected to be formed along the c-axis, and novel
Josephson effects due to the multi-gap nature are also suggested in these
superconductors.Comment: 5 pages, 4 figure
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