32 research outputs found
Magnetization Measurements on Single Crystals of Superconducting Ba0.6K0.4BiO3
Extensive measurements of the magnetization of superconducting single crystal
samples of Ba0.6K0.4BiO3} have been made using SQUID and cantilever force
magnetometry at temperatures ranging between 1.3 and 350 K and in magnetic
fields from near zero to 27 T. Hysteresis curves of magnetization versus field
allow a determination of the thermodynamic critical field, the reversibility
field, and the upper critical field as a function of temperature. The lower
critical field is measured seperately and the Ginzburg-Landau parameter is
found to be temperature dependent. All critical fields have higher T = 0 limits
than have been previously noted and none of the temperature dependence of the
critical fields follow the expected power laws leading to possible alternate
interpretation of the thermodynamic nature of the superconducting transition.Comment: 33 pages, 11 figures, accepted for publication in Philosophical
Magazine B on 7 August 1999. This paper supplies the experimental details for
the argument presented in our PRL 82 (1999) p. 4532-4535 (also at
cond-mat/9904288
The activated torsion oscillation magnetometer
The activated torsion oscillation magnetometer exploits the mechanical
resonance of a cantilever beam, driven by the torque exerted on the sample by
an ac field applied perpendicularly to the film plane. We describe a model for
the cantilever dynamics which leads to the calculation of the cantilever
dynamic profile and allows the mechanical sensitivity of the instrument to be
expressed in terms of the minimum electronically detectable displacement. We
have developed a capacitance detector of small oscillations which is able to
detect displacements of the order of 0.1 nm. We show that sensitivities of the
order of 0.5(10-11 Am2 can be in principle achieved. We will subsequently
describe the main features of the ATOM prototype which we have built and
tested, with particular attention to the design solutions which have been
adopted in order to reduce the effects of parasitic vibrations due either to
acoustic noise, originating from the ac field coil, or to eddy currents in the
capacitor electrodes. The instrument is mounted in a continuous flow cryostat
and can work in the 4.2-300 K temperature range. Finally, we will show that our
experimental set-up has a second mode of operation, named Torsion Induction
Magnetometer (TIM).Comment: Invited Talk at the Moscow International Symposium on Magnetism, 2002
to appear in the J. Mag. Mag. Mat Revised versio
Magnetic Determination of under Accurate Alignment in (TMTSF)ClO
Cantilever magnetometry has been used to measure the upper critical magnetic
field of the quasi-one dimensional molecular organic superconductor
(TMTSF)ClO. From simultaneous resistivity and torque magnetization
experiments conducted under precise field alignment, at low
temperature is shown to reach 5T, nearly twice the Pauli paramagnetic limit
imposed on spin singlet superconductors. These results constitute the first
thermodynamic evidence for a large in this system and provide support
for spin triplet pairing in this unconventional superconductorComment: Submitted July 1, 2003, Accepted December 9, 2003, Physical Review
Letter
Experimental Evidence of a Haldane Gap in an S = 2 Quasi-linear Chain Antiferromagnet
The magnetic susceptibility of the quasi-linear chain Heisenberg
antiferromagnet (2,-bipyridine)trichloromanganese(III), MnCl_{3}(bipy), has
been measured from 1.8 to 300 K with the magnetic field, H, parallel and
perpendicular to the chains. The analyzed data yield and K. The magnetization, M, has been studied at 30 mK and 1.4 K in H up to 16
T. No evidence of long-range order is observed. Depending on crystal
orientation, at 30 mK until a critical field is achieved ( and $H_{c\bot} = 1.8\pm 0.2 T), where M increases continuously
as H is increased. These results are interpreted as evidence of a Haldane gap.Comment: 11 pages, 4 figure
Postoperative outcomes in oesophagectomy with trainee involvement
BACKGROUND: The complexity of oesophageal surgery and the significant risk of morbidity necessitates that oesophagectomy is predominantly performed by a consultant surgeon, or a senior trainee under their supervision. The aim of this study was to determine the impact of trainee involvement in oesophagectomy on postoperative outcomes in an international multicentre setting. METHODS: Data from the multicentre Oesophago-Gastric Anastomosis Study Group (OGAA) cohort study were analysed, which comprised prospectively collected data from patients undergoing oesophagectomy for oesophageal cancer between April 2018 and December 2018. Procedures were grouped by the level of trainee involvement, and univariable and multivariable analyses were performed to compare patient outcomes across groups. RESULTS: Of 2232 oesophagectomies from 137 centres in 41 countries, trainees were involved in 29.1 per cent of them (n = 650), performing only the abdominal phase in 230, only the chest and/or neck phases in 130, and all phases in 315 procedures. For procedures with a chest anastomosis, those with trainee involvement had similar 90-day mortality, complication and reoperation rates to consultant-performed oesophagectomies (P = 0.451, P = 0.318, and P = 0.382, respectively), while anastomotic leak rates were significantly lower in the trainee groups (P = 0.030). Procedures with a neck anastomosis had equivalent complication, anastomotic leak, and reoperation rates (P = 0.150, P = 0.430, and P = 0.632, respectively) in trainee-involved versus consultant-performed oesophagectomies, with significantly lower 90-day mortality in the trainee groups (P = 0.005). CONCLUSION: Trainee involvement was not found to be associated with significantly inferior postoperative outcomes for selected patients undergoing oesophagectomy. The results support continued supervised trainee involvement in oesophageal cancer surgery
Outcomes in adult pectus excavatum patients undergoing Nuss repair
MennatAllah M Ewais, Shivani Chaparala, Rebecca Uhl, Dawn E JaroszewskiDepartment of Cardiothoracic Surgery, Mayo Clinic Hospital, Phoenix, AZ, USA Abstract: Pectus excavatum (PEx) is one of the most common congenital chest wall deformities. Depending on the severity, presentation of PEx may range from minor cosmetic issues to disabling cardiopulmonary symptoms. The effect of PEx on adult patients has not been extensively studied. Symptoms may not occur until the patient ages, and they may worsen over the years. More recent publications have implied that PEx may have significant cardiopulmonary implications and repair is of medical benefit. Adults presenting for PEx repair can undergo a successful repair with a minimally invasive “Nuss” approach. Resolution of symptoms, improved quality of life, and satisfying results are reported. Keywords: complications, minimally invasive surgery, quality of lif