361 research outputs found
Transrenal Ureteral Embolization Utilizing Amplatzer Vascular Plugs and N-Butyl Cyanoacrylate Glue.
This retrospective study presents three consecutive patients who underwent bilateral ureteral occlusion using the Amplatzer vascular plugs and N-butyl cyanoacrylate glue sandwich method. The patients were 63- and 65-year-old males and a 79-year-old female. Indications for the procedure included severe cystitis and complex vesicular fistulas unresponsive to urinary diversion. All three patients had immediate resolution of urinary leakage, resulting in symptom relief throughout the follow-up period. There were no procedure-related complications or side effects
Anisotropies of the lower and upper critical fields in MgB single crystals
The temperature dependence of the London penetration depth () and
coherence length () has been deduced from Hall probe magnetization
measurements in high quality MgB single crystals in the two main
crystallographic directions. We show that, in contrast to conventional
superconductors, MgB is characterized by two different anisotropy
parameters ( and ) which strongly differ at low temperature and merge at .
These results are in very good agreement with recent calculations in weakly
coupled two bands suprerconductors (Phys. Rev. B, 66, 020509(R) (2002).Comment: 4 pages, 4 figure
Evidence for Nodal superconductivity in SrScFePO
Point contact Andreev reflection spectra have been taken as a function of
temperature and magnetic field on the polycrystalline form of the newly
discovered iron-based superconductor Sr2ScFePO3. A zero bias conductance peak
which disappears at the superconducting transition temperature, dominates all
of the spectra. Data taken in high magnetic fields show that this feature
survives until 7T at 2K and a flattening of the feature is observed in some
contacts. Here we inspect whether these observations can be interpreted within
a d-wave, or nodal order parameter framework which would be consistent with the
recent theoretical model where the height of the P in the Fe-P-Fe plane is key
to the symmetry of the superconductivity. However, in polycrystalline samples
care must be taken when examining Andreev spectra to eliminate or take into
account artefacts associated with the possible effects of Josephson junctions
and random alignment of grains.Comment: Published versio
Evidence for Supercurrent Connectivity in Conglomerate Particles in NdFeAsO1-d
Here we use global and local magnetometry and Hall probe imaging to
investigate the electromagnetic connectivity of the superconducting current
path in the oxygen-deficient fluorine-free Nd-based oxypnictides. High
resolution transmission electron microscopy and scanning electron microscopy
show strongly-layered crystallites, evidence for a ~ 5nm amorphous oxide around
individual particles, and second phase neodymium oxide which may be responsible
for the large paramagnetic background at high field and at high temperatures.
From global magnetometry and electrical transport measurements it is clear
that there is a small supercurrent flowing on macroscopic sample dimensions
(mm), with a lower bound for the average (over this length scale) critical
current density of the order of 103 A/cm2. From magnetometry of powder samples
and local Hall probe imaging of a single large conglomerate particle ~120
microns it is clear that on smaller scales, there is better current
connectivity with a critical current density of the order of 5 x 104 A/cm2. We
find enhanced flux creep around the second peak anomaly in the magnetisation
curve and an irreversibility line significantly below Hc2(T) as determined by
ac calorimetry.Comment: 11 pages, 4 figure
Superconducting gap structure and pinning in disordered MgB2 films
We have performed a comparative study of two thin films of magnesium diboride
(MgB2) grown by different techniques. The critical current density at different
temperatures and magnetic fields was evaluated from magnetisation curves, the
structure of superconducting order parameter was obtained from point-contact
spectroscopy, and the scattering rates were evaluated by fitting the
temperature dependent normal-state resistivity to the two-band model. The films
have similar critical temperatures close to 39 K, but the upper critical fields
were different by a factor of 2 (5.2T and 2.5 T at 20 K). We have found that
the film with higher Hc2 also had stronger scattering in the sigma band and
smaller value of the superconducting gap in this band. As the scattering in
sigma band is primarily due to the defects in boron plane, our results are
consistent with the assumption that disordering the boron planes leads to
enhanced Hc2 and better pinning properties in magnetic field.Comment: Paper presented at EUCAS'0
Phase 3 Trial of 177Lu-Dotatate for Midgut Neuroendocrine Tumors
Background Patients with advanced midgut neuroendocrine tumors who have had disease progression during first-line somatostatin analogue therapy have limited therapeutic options. This randomized, controlled trial evaluated the efficacy and safety of lutetium-177 (177Lu)-Dotatate in patients with advanced, progressive, somatostatin-receptor-positive midgut neuroendocrine tumors. Methods We randomly assigned 229 patients who had well-differentiated, metastatic midgut neuroendocrine tumors to receive either 177Lu-Dotatate (116 patients) at a dose of 7.4 GBq every 8 weeks (four intravenous infusions, plus best supportive care including octreotide long-acting repeatable [LAR] administered intramuscularly at a dose of 30 mg) (177Lu-Dotatate group) or octreotide LAR alone (113 patients) administered intramuscularly at a dose of 60 mg every 4 weeks (control group). The primary end point was progression-free survival. Secondary end points included the objective response rate, overall survival, safety, and the side-effect profile. The final analysis of overall survival will be conducted in the future as specified in the protocol; a prespecified interim analysis of overall survival was conducted and is reported here. Results At the data-cutoff date for the primary analysis, the estimated rate of progression-free survival at month 20 was 65.2% (95% confidence interval [CI], 50.0 to 76.8) in the 177Lu-Dotatate group and 10.8% (95% CI, 3.5 to 23.0) in the control group. The response rate was 18% in the 177Lu-Dotatate group versus 3% in the control group (P<0.001). In the planned interim analysis of overall survival, 14 deaths occurred in the 177Lu-Dotatate group and 26 in the control group (P=0.004). Grade 3 or 4 neutropenia, thrombocytopenia, and lymphopenia occurred in 1%, 2%, and 9%, respectively, of patients in the 177Lu-Dotatate group as compared with no patients in the control group, with no evidence of renal toxic effects during the observed time frame. Conclusions Treatment with 177Lu-Dotatate resulted in markedly longer progression-free survival and a significantly higher response rate than high-dose octreotide LAR among patients with advanced midgut neuroendocrine tumors. Preliminary evidence of an overall survival benefit was seen in an interim analysis; confirmation will be required in the planned final analysis. Clinically significant myelosuppression occurred in less than 10% of patients in the 177Lu-Dotatate group. (Funded by Advanced Accelerator Applications; NETTER-1 ClinicalTrials.gov number, NCT01578239 ; EudraCT number 2011-005049-11
The effect of magnetic field on the two superconducting gaps in MgB2
Double-gap superconductivity in an epitaxial MgB2 film has been studied by
means of point-contact spectroscopy in magnetic field up to 8 Tesla. The
relatively fast disappearance of the feature associated with the pi-band gap at
a field around 1 T is caused by the line broadening due to strong pair breaking
rather than to a collapse of the double-gap state. This pair breaking was found
to increase linearly with field. Field dependences of the order parameters
Delta_pi and Delta_sigma in the pi and sigma bands were measured in field
applied parallel and perpendicular to the film, at T = 4.2 K. In perpendicular
field, both order parameters survive to a common Hc2, which is about 6.5 T for
this direction. In parallel field, the decrease of Delta_sigma is much more
gradual, consistent with the Hc2 being about 4 times greater in this
ori-entation. The difference in Delta_pi measured in the two field orientations
is however smaller than the difference of Delta_sigma. We compare these results
with the data on tunnelling spectroscopy and specific heat measurements of MgB2
single crystals and find consistency between the different experimental
approaches.Comment: 4 pages, 5 figures Revised: discussion of the distribution of gap
value
Point-Contact Spectroscopy in MgB_2: from Fundamental Physics to Thin-Film Characterization
In this paper we highlight the advantages of using point-contact spectroscopy
(PCS) in multigap superconductors like MgB_2, both as a fundamental research
tool and as a non-destructive diagnostic technique for the optimization of
thin-film characteristics. We first present some results of crucial fundamental
interest obtained by directional PCS in MgB_2 single crystals, for example the
temperature dependence of the gaps and of the critical fields and the effect of
a magnetic field on the gap amplitudes. Then, we show how PCS can provide
useful information about the surface properties of MgB_2 thin films (e.g. Tc,
gap amplitude(s), clean or dirty-limit conditions) in view of their
optimization for the fabrication of tunnel and Josephson junctions for
applications in superconducting electronics.Comment: 11 pages, 7 figures; Proceedings of 6th EUCAS Conference (14-18
September 2003, Sorrento - Italy
Tumor growth rate as a metric of progression, response, and prognosis in pancreatic and intestinal neuroendocrine tumors
Background: Lanreotide depot/autogel antitumor activity in intestinal/pancreatic neuroendocrine tumors (NETs) was demonstrated in the phase-3 CLARINET study (NCT00353496), based on significantly prolonged progression-free survival (PFS) versus placebo.
Methods: During CLARINET, patients with metastatic intestinal/pancreatic NETs received lanreotide depot/autogel 120 mg or placebo every 4 weeks for 96 weeks. Imaging data (response evaluation criteria in solid tumors [RECIST] v1.0, centrally reviewed) were re-evaluated in this post hoc analysis of tumor growth rate (TGR) in NETs. TGR (%/month) was calculated from two imaging scans during relevant periods: pre-treatment (TGR0); 12-24 weeks before randomization versus baseline; each treatment visit versus baseline (TGRTx-0); between consecutive treatment visits (TGRTx-Tx). To assess TGR as a measure of prognosis, PFS was compared for TGR0 subgroups stratified by optimum TGR0 cut-off; a multivariate analysis was conducted to identify prognostic factors for PFS.
Results: TGR0 revealed tumors growing during pre-treatment (median [interquartile range] TGR0: lanreotide 2.1%/month [0.2; 6.1]; placebo 2.7%/month [0.15; 6.8]), contrary to RECIST status. TGR was significantly reduced by 12 weeks with lanreotide versus placebo (difference in least-square mean TGR0-12 of - 2.9 [- 5.1, - 0.8], p = 0.008), a difference that was maintained at most subsequent visits. TGR0 > 4%/month had greater risk of progression/death than ≤4%/month (hazard ratio 4.1; [95% CI 2.5-6.5]; p < 0.001); multivariate analysis revealed lanreotide treatment, progression at baseline, TGR0, hepatic tumor load, and primary tumor type were independently associated with PFS.
Conclusions: TGR provides valuable information on tumor activity and prognosis in patients with metastatic intestinal/pancreatic NETs, and identifies early lanreotide depot/autogel antitumor activity.
Trial registration: Retrospective registration, 18 July 2006; EudraCT: 2005-004904-35; ClinicalTrials.gov: NCT00353496
Treatment challenges in and outside a specialist network setting: Pancreatic neuroendocrine tumours
Pancreatic Neuroendocrine Neoplasms comprise a group of rare tumours with special biology, an often indolent behaviour and particular diagnostic and therapeutic requirements. The specialized biochemical tests and radiological investigations, the complexity of surgical options and the variety of medical treatments that require individual tailoring, mandate a multidisciplinary approach that can be optimally achieved through an organized network. The present study describes currents concepts in the management of these tumours as well as an insight into the challenges of delivering the pathway in and outside a Network
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