Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
1.
Nat Mater ; 22(9): 1100-1105, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37537357

RESUMO

A quantum anomalous Hall (QAH) insulator is characterized by quantized Hall and vanishing longitudinal resistances at zero magnetic field that are protected against local perturbations and independent of sample details. This insensitivity makes the microscopic details of the local current distribution inaccessible to global transport measurements. Accordingly, the current distributions that give rise to transport quantization are unknown. Here we use magnetic imaging to directly visualize the transport current in the QAH regime. As we tune through the QAH plateau by electrostatic gating, we clearly identify a regime in which the sample transports current primarily in the bulk rather than along the edges. Furthermore, we image the local response of equilibrium magnetization to electrostatic gating. Combined, these measurements suggest that the current flows through incompressible regions whose spatial structure can change throughout the QAH regime. Identification of the appropriate microscopic picture of electronic transport in QAH insulators and other topologically non-trivial states of matter is a crucial step towards realizing their potential in next-generation quantum devices.

2.
Nat Commun ; 14(1): 2055, 2023 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-37045826

RESUMO

A growing number of two-dimensional superconductors are being discovered in the family of exfoliated van der Waals materials. Due to small sample volume, the superfluid response of these materials has not been characterized. Here, we use a local magnetic probe to directly measure this key property of the tunable, gate-induced superconducting state in MoS2. We find that the backgate changes the transition temperature non-monotonically whereas the superfluid stiffness at low temperature and the normal state conductivity monotonically increase. In some devices, we find direct signatures in agreement with a Berezinskii-Kosterlitz-Thouless transition, whereas in others we find a broadened onset of the superfluid response. We show that the observed behavior is consistent with disorder playing an important role in determining the properties of superconducting MoS2. Our work demonstrates that magnetic property measurements are within reach for superconducting devices based on exfoliated sheets and reveals that the superfluid response significantly deviates from simple BCS-like behavior.

3.
Rev Sci Instrum ; 92(8): 083704, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-34470407

RESUMO

We report a scanning superconducting quantum interference device (SQUID) microscope in a cryogen-free dilution refrigerator with a base temperature at the sample stage of at least 30 mK. The microscope is rigidly mounted to the mixing chamber plate to optimize thermal anchoring of the sample. The microscope housing fits into the bore of a superconducting vector magnet, and our design accommodates a large number of wires connecting the sample and sensor. Through a combination of vibration isolation in the cryostat and a rigid microscope housing, we achieve relative vibrations between the SQUID and the sample that allow us to image with micrometer resolution over a 150 µm range while the sample stage temperature remains at base temperature. To demonstrate the capabilities of our system, we show images acquired simultaneously of the static magnetic field, magnetic susceptibility, and magnetic fields produced by a current above a superconducting micrometer-scale device.

4.
Science ; 366(6462): 221-226, 2019 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-31601766

RESUMO

Although crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches exist for spatially modulating their properties. In this study, we demonstrate disorder-free control, on the micrometer scale, over the superconducting state in samples of the heavy-fermion superconductor CeIrIn5 We pattern crystals by focused ion beam milling to tailor the boundary conditions for the elastic deformation upon thermal contraction during cooling. The resulting nonuniform strain fields induce complex patterns of superconductivity, owing to the strong dependence of the transition temperature on the strength and direction of strain. These results showcase a generic approach to manipulating electronic order on micrometer length scales in strongly correlated matter without compromising the cleanliness, stoichiometry, or mean free path.

5.
J Orthop Res ; 6(4): 525-30, 1988.
Artigo em Inglês | MEDLINE | ID: mdl-2837555

RESUMO

Addition of CoCl2 solutions to the culture media of confluent monolayers of lapine or human synoviocytes stimulated their production of the neutral proteinases collagenase, gelatinase, and caseinase. With lapine cells, maximum stimulation occurred at 10(-7) M CoCl2, while human cells required 10(-4)-10(-5) M CoCl2 to achieve a maximum stimulation. Production of prostaglandin E2 by lapine cells was enhanced some 30-40% by concentrations of CoCl2 that maximally stimulated synthesis of the neutral proteinases, whereas all concentrations of CoCl2 slightly depressed the production of prostaglandin E2 by human cells. Lapine synovial cells that had been stimulated by CoCl2 also produced a substance, or substances, that provoked the synthesis of collagenase, gelatinase, caseinase, and prostaglandin E2 by monolayers of articular chondrocytes. Chondrocytes themselves, however, resisted activation by CoCl2. These findings may be relevant to the aseptic loosening of joint prostheses.


Assuntos
Cobalto/farmacologia , Colagenase Microbiana/biossíntese , Biossíntese de Proteínas , Proteínas , Membrana Sinovial/metabolismo , Animais , Cartilagem Articular/efeitos dos fármacos , Cartilagem Articular/metabolismo , Células Cultivadas , Dinoprostona , Gelatinases , Substâncias de Crescimento/biossíntese , Humanos , Prótese Articular , Metaloendopeptidases/biossíntese , Pepsina A/biossíntese , Peptídeo Hidrolases/biossíntese , Prostaglandinas E/biossíntese , Falha de Prótese , Coelhos , Membrana Sinovial/efeitos dos fármacos
6.
J Bone Joint Surg Br ; 76(2): 252-7, 1994 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-8113286

RESUMO

From 1969 through 1982, 305 hips in 290 patients had total hip arthroplasty for failed femoral intertrochanteric osteotomy. Of these, we reviewed 215 hips (70.5%) with a minimum follow-up of five years. The results were good or excellent in 79%, but there were technical problems at operation in 23% and a total perioperative complication rate of 11.8%. Late complications occurred in 13.1% including seven late infections (3.2%). At a mean follow-up of ten years, 39 hips had been revised (18.1%), there was probable loosening in 19.5% of stems and 12.6% of cups and possible loosening in 11.4% of stems and 7.2% of cups. The cumulative probability of failure at ten years was 20.6%. We recommend that intertrochanteric osteotomy be advised, planned and executed bearing in mind the possible need for a subsequent total hip arthroplasty, and that screws and plates should be routinely removed soon after union of the osteotomy.


Assuntos
Fêmur/cirurgia , Prótese de Quadril , Osteotomia , Idoso , Artrite/cirurgia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/etiologia , Falha de Prótese , Reoperação , Falha de Tratamento
7.
Adv Perit Dial ; 11: 202-7, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-8534706

RESUMO

From January 1989 to June 1994 we examined the success rate of fluoroscopically guided stiff wire manipulation of malfunctioning peritoneal dialysis catheters (PDCs) at St. Paul's Hospital, Saskatoon. There were 341 (201 male, 140 female) patients with a PDC. There were 118 manipulations (70 initial, 48 remanipulations) for malposition, fibrin clot, or kinked catheter. Single-cuff Tenckhoff catheters accounted for 95% of manipulated PDCs. No complications including peritonitis, exit-site infections, ruptured catheter, or bowel perforation were reported postmanipulation. A successful manipulation was defined as a functional PDC at 30 days postmanipulation. There was an overall success rate of 64%-67% for initial manipulations (IM) and 48% for remanipulations (RM). Ninety percent of those PDCs requiring IM occurred within 42 days of surgical insertion. RM occurred on average 55 days after IM. There were no risk factors identified that predisposed patients for PDC manipulation. This success rate for combined IM and RM of PDCs is higher than those rates quoted in the literature (27%-42%). We conclude that fluoroscopically guided stiff wire manipulation of PDCs, including repeated attempts, is a safe and effective way of prolonging PDC life, thus avoiding the risks of repeated surgery, improving quality of life, and decreasing health care costs.


Assuntos
Cateteres de Demora/efeitos adversos , Diálise Peritoneal/instrumentação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Falha de Equipamento , Feminino , Fluoroscopia , Humanos , Masculino , Pessoa de Meia-Idade , Diálise Peritoneal/efeitos adversos , Radiografia Intervencionista , Estudos Retrospectivos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA