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 Hc2H_{c2} under Accurate Alignment in (TMTSF)2_2ClO4_4

Cantilever magnetometry has been used to measure the upper critical magnetic field $H_{c2}$ of the quasi-one dimensional molecular organic superconductor (TMTSF)$_2$ClO$_4$. From simultaneous resistivity and torque magnetization experiments conducted under precise field alignment, $H_{c2}$ 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 $H_{c2}$ 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 $S = 2$ quasi-linear chain Heisenberg antiferromagnet (2,$2'$-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 $g\approx 2$ and $J\approx 35$ 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, $M\approx 0$ at 30 mK until a critical field is achieved ($H_{c\|} = 1.2\pm 0.2 T$ 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