1,281 research outputs found
Effects of Co substitution on thermodynamic and transport properties and anisotropic in Ba(FeCo)As single crystals
Single crystalline samples of Ba(FeCo)As with
have been grown and characterized via microscopic, thermodynamic and transport
measurements. With increasing Co substitution, the thermodynamic and transport
signatures of the structural (high temperature tetragonal to low temperature
orthorhombic) and magnetic (high temperature non magnetic to low temperature
antiferromagnetic) transitions are suppressed at a rate of roughly 15 K per
percent Co. In addition, for superconductivity is stabilized,
rising to a maximum of approximately 23 K for and
decreasing for higher values. The phase diagram for
Ba(FeCo)As indicates that either superconductivity can
exist in both low temperature crystallographic phases or that there is a
structural phase separation. Anisotropic, superconducting, upper critical field
data () show a significant and clear change in anisotropy between
samples that have higher temperature structural phase transitions and those
that do not. These data show that the superconductivity is sensitive to the
suppression of the higher temperature phase transition
Pharmacologic Treatment for Pediatric Gastroparesis: A Review of the Literature
There have been a number of agents that have been tried for treatment of gastroparesis over the past 3 decades, with varying levels of success. Guidelines exist for the management of gastroparesis in adults; however, even though the cause of gastroparesis in children is similar to that in adults, no guidelines exist for treating pediatric gastroparesis as studies on the topic are limited. With what little information we have on pediatric gastroparesis, medications used in children's studies do not seem to demonstrate the same results as in adult patients with gastroparesis; thus, future studies of whether certain medications are effective for treating pediatric gastroparesis and at what dose still need to be conducted. Pharmacological treatment options for pediatric gastroparesis do not show a clear correlation of resolving or even maintaining gastroparesis-associated symptoms or disease state. This article reviews the available studies of drugs that have shown some efficacy, with an emphasis on pediatric studies
Thermal expansion and magnetostriction of pure and doped RAgSb2 (R = Y, Sm, La) single crystals
Data on temperature-dependent, anisotropic thermal expansion in pure and
doped RAgSb2 (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest
relation and heat capacity measurements, uniaxial pressure derivatives for long
range magnetic ordering and charge density wave transition temperatures are
evaluated and compared with the results of the direct measurements under
hydrostatic pressure. In-plane and c-axis pressure have opposite effect on the
phase transitions in these materials, with in-plane effects being significantly
weaker. Quantum oscillations in magnetostriction were observed for the three
pure compounds, with the possible detection of new frequencies in SmAgSb2 and
LaAgSb2. The uniaxial (along the c-axis) pressure derivatives of the dominant
extreme orbits (beta) were evaluated for YAgSb2 and LaAgSb2
The Two-Stage Ipsilateral Fibular Transfer for Tibial Defect Following Tumour Excision
Method. We performed a two-stage vascularized ipsilateral fibular
graft transfer for segmental tibial defect following excision of malignant bone tumours
Momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals measured by angle resolved photoemission spectroscopy
We use angle resolved photoemission spectroscopy (ARPES) to study the
momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals.
We find that the Gamma hole pocket is fully gapped below the superconducting
transition temperature. The value of the superconducting gap is 15 +- 1.5 meV
and its anisotropy around the hole pocket is smaller than 20% of this value.
This is consistent with an isotropic or anisotropic s-wave symmetry of the
order parameter or exotic d-wave symmetry with nodes located off the Fermi
surface sheets. This is a significant departure from the situation in the
cuprates, pointing to possibility that the superconductivity in the iron
arsenic based system arises from a different mechanism.Comment: 4 pages, 3 figure
Flux pinning in (1111) iron-pnictide superconducting crystals
Local magnetic measurements are used to quantitatively characterize
heterogeneity and flux line pinning in PrFeAsO_1-y and NdFeAs(O,F)
superconducting single crystals. In spite of spatial fluctuations of the
critical current density on the macroscopic scale, it is shown that the major
contribution comes from collective pinning of vortex lines by microscopic
defects by the mean-free path fluctuation mechanism. The defect density
extracted from experiment corresponds to the dopant atom density, which means
that dopant atoms play an important role both in vortex pinning and in
quasiparticle scattering. In the studied underdoped PrFeAsO_1-y and NdFeAs(O,F)
crystals, there is a background of strong pinning, which we attribute to
spatial variations of the dopant atom density on the scale of a few dozen to
one hundred nm. These variations do not go beyond 5% - we therefore do not find
any evidence for coexistence of the superconducting and the antiferromagnetic
phase. The critical current density in sub-T fields is characterized by the
presence of a peak effect, the location of which in the (B,T)-plane is
consistent with an order-disorder transition of the vortex lattice.Comment: 12 pages, submitted to Phys Rev.
Upper and lower critical magnetic fields of superconducting NdFeAsO1−xFx single crystals studied by Hall-probe magnetization and specific heat
International audienceThe upper and lower critical fields have been deduced from specific heat and Hall-probe magnetization measurements in nonoptimally doped Nd O,F FeAs single crystals Tc 32-35 K . The anisotropy of the penetration depth is temperature independent and on the order of 4.0 1.5. Similarly specific-heat data lead to an anisotropy of the coherence length 5.5 1.5 close to Tc. Our results suggest the presence of rather large thermal fluctuations and the existence of a vortex liquid phase over a broad temperature range 5 K large at 2 T
Leiomyosarcomas of Vascular Origin in the Extremity
Between 1996 and 2006 a total of 278 patients with soft tissue
Leiomyosarcoma were treated at our centre. We identified 16
patients (5.8%) where the tumour directly arose from the blood
vessels. These tumours were studied to determine their prognosis
and behaviour. All tumors were in the lower limbs: 11 from the
femoral vein, 3 popliteal vein, and 2 from the posterior tibial
vein. Mean tumour size was 10.4 cm (3 to 33). Histological
grade was high in all patients. Surgical treatment was amputation
in one, excision with or without vascular reconstruction in 12
followed by radiotherapy, and 3 patients had no surgery because of
advanced disease at diagnosis. Seven out of the 16 patients
(44%) had metastasis at diagnosis, and five patients without
metastasis at diagnosis rapidly developed metastases at a median
time of 5 months from diagnosis (2–30 months). The overall
survival of the patients at 5 years was 25% which was
considerably worse than those with nonvascular leiomyosarcoma. We
conclude that patients with leiomyosarcoma of vascular origin have
a very high risk of metastases and poor prognosis when treated in
the conventional way
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