Autonomous error correction of a single logical qubit using two transmons.

Large-scale quantum computers will inevitably need quantum error correction to protect information against decoherence. Traditional error correction typically requires many qubits, along with high-efficiency error syndrome measurement and real-time feedback. Autonomous quantum error correction instead uses steady-state bath engineering to perform the correction in a hardware-efficient manner. In this work, we develop a new autonomous quantum error correction scheme that actively corrects single-photon loss and passively suppresses low-frequency dephasing, and we demonstrate an important experimental step towards its full implementation with transmons. Compared to uncorrected encoding, improvements are experimentally witnessed for the logical zero, one, and superposition states. Our results show the potential of implementing hardware-efficient autonomous quantum error correction to enhance the reliability of a transmon-based quantum information processor.

Intraperitoneal Loss of Pelvic Array Pin During Navigated Total Hip Arthroplasty.

Pelvic array pin placement during navigated total hip arthroplasty has been known to cause complications; however, most of them are minor. We report a 78-year-old female who underwent a routine computer-navigated total hip replacement which was subsequently complicated by complete loss of the pelvic array pin requiring retrieval via laparotomy. No structures were injured despite the surrounding urological, vascular, and visceral anatomy. The patient recovered and subsequently underwent a total hip arthroplasty without complication 6 weeks later. This case illustrates the dangers of inserting a pelvic array pin within patients with poor bone quality and highlights necessary considerations of pin design and surgical techniques to minimize this complication.

Intraosseous Regional Prophylactic Antibiotics Decrease the Risk of Prosthetic Joint Infection in Primary TKA: A Multicenter Study.

BACKGROUND: Recent studies have demonstrated that the administration of regional prophylactic antibiotics by intraosseous (IO) injection achieves tissue concentrations around the knee that are 10- to 15-fold higher than intravenous (IV) delivery of prophylactic antibiotics. It is currently unknown whether the use of regional prophylactic antibiotics for primary TKA would result in a lower risk of prosthetic joint infection (PJI). QUESTIONS/PURPOSES: (1) Is IO injection of prophylactic antibiotics associated with a decreased risk of early (< 12 months) deep PJI compared with traditional IV prophylactic antibiotics? (2) What other patient factors are associated with an increased risk of early PJI after TKA, and do regional prophylactic antibiotics influence these risk factors? (3) Can IO antibiotics be administered to all patients, and what complications occurred from the delivery of IO prophylactic antibiotics? METHODS: A retrospective comparative study of all primary TKAs (1909 TKAs) over a 5-year period (January 2013 to December 2017) was performed to determine the risk of early PJI. Three primary TKAs did not meet the study inclusion criteria and were excluded from the study, leaving a total of 1906 TKAs (725 IO, 1181 IV) for analysis at a minimum of 12 months after index procedure. Both cohorts exhibited similar ages, BMI, and American Society of Anesthesiologists (ASA) grades; however, a greater proportion of patients in the IO cohort were smokers (p = 0.01), while a greater proportion of patients were diabetic in the IV cohort (p = 0.006). The PJI risk between IO and IV delivery techniques was compared while adjusting for patient demographics and medical comorbidities. Complications related to IO delivery-inability to administer via IO technique, compartment syndrome, fat embolism, and red man syndrome with vancomycin use-were recorded. RESULTS: The delivery of regional prophylactic antibiotics by the IO technique resulted in a lower PJI risk than IV prophylactic antibiotics (0.1% [1 of 725] compared with 1.4% [16 of 1181]; relative risk 0.10 [95% CI 0.01 to 0.77]; p = 0.03). BMI (ß = -0.17; standard error = 0.08; p = 0.02), diabetes (ß = -1.80; standard error = 0.75; p = 0.02), and renal failure (ß = -2.37; standard error = 0.84; p = 0.01) were factors associated with of PJI, while smoking, sex, and ASA score were not contributing factors (p > 0.05). Although BMI, diabetes, and renal failure were identified as infection risk factors, the use of IO antibiotics in these patients did not result in a lower PJI risk compared with IV antibiotics (p > 0.05). IO antibiotics were able to be successfully administered to all patients in this cohort, and there were no complications related to the delivery of IO antibiotics. CONCLUSION: Surgeons should consider administering regional prophylactic antibiotics in primary TKA to reduce the risk of early PJI. Future randomized prospective clinical trials are needed to validate the efficacy of regional prophylactic antibiotics in reducing the PJI risk in primary TKA. LEVEL OF EVIDENCE: Level III, therapeutic study.

Tuning Electrical Conductance of MoS2 Monolayers through Substitutional Doping.

Tuning electrical conductivity of semiconducting materials through substitutional doping is crucial for fabricating functional devices. This, however, has not been fully realized in two-dimensional (2D) materials due to the difficulty of homogeneously controlling the dopant concentrations and the lack of systematic study of the net impact of substitutional dopants separate from that of the unintentional doping from the device fabrication processes. Here, we grow wafer-scale, continuous MoS2 monolayers with tunable concentrations of Nb and Re and fabricate devices using a polymer-free approach to study the direct electrical impact of substitutional dopants in MoS2 monolayers. In particular, the electrical conductivity of Nb doped MoS2 in the absence of electrostatic gating is reproducibly tuned over 7 orders of magnitude by controlling the Nb concentration. Our study further indicates that the dopant carriers do not fully ionize in the 2D limit, unlike in their three-dimensional analogues, which is explained by weaker charge screening and impurity band conduction. Moreover, we show that the dopants are stable, which enables the doped films to be processed as independent building blocks that can be used as electrodes for functional circuitry.

Wafer-scale synthesis of monolayer two-dimensional porphyrin polymers for hybrid superlattices.

The large-scale synthesis of high-quality thin films with extensive tunability derived from molecular building blocks will advance the development of artificial solids with designed functionalities. We report the synthesis of two-dimensional (2D) porphyrin polymer films with wafer-scale homogeneity in the ultimate limit of monolayer thickness by growing films at a sharp pentane/water interface, which allows the fabrication of their hybrid superlattices. Laminar assembly polymerization of porphyrin monomers could form monolayers of metal-organic frameworks with Cu2+ linkers or covalent organic frameworks with terephthalaldehyde linkers. Both the lattice structures and optical properties of these 2D films were directly controlled by the molecular monomers and polymerization chemistries. The 2D polymers were used to fabricate arrays of hybrid superlattices with molybdenum disulfide that could be used in electrical capacitors.

Two-Dimensional Material Tunnel Barrier for Josephson Junctions and Superconducting Qubits.

Quantum computing based on superconducting qubits requires the understanding and control of the materials, device architecture, and operation. However, the materials for the central circuit element, the Josephson junction, have mostly been focused on using the AlOx tunnel barrier. Here, we demonstrate Josephson junctions and superconducting qubits employing two-dimensional materials as the tunnel barrier. We batch-fabricate and design the critical Josephson current of these devices via layer-by-layer stacking N layers of MoS2 on the large scale. Based on such junctions, MoS2 transmon qubits are engineered and characterized in a bulk superconducting microwave resonator for the first time. Our work allows Josephson junctions to access the diverse material properties of two-dimensional materials that include a wide range of electrical and magnetic properties, which can be used to study the effects of different material properties in superconducting qubits and to engineer novel quantum circuit elements in the future.

Layer-by-layer assembly of two-dimensional materials into wafer-scale heterostructures.

High-performance semiconductor films with vertical compositions that are designed to atomic-scale precision provide the foundation for modern integrated circuitry and novel materials discovery. One approach to realizing such films is sequential layer-by-layer assembly, whereby atomically thin two-dimensional building blocks are vertically stacked, and held together by van der Waals interactions. With this approach, graphene and transition-metal dichalcogenides-which represent one- and three-atom-thick two-dimensional building blocks, respectively-have been used to realize previously inaccessible heterostructures with interesting physical properties. However, no large-scale assembly method exists at present that maintains the intrinsic properties of these two-dimensional building blocks while producing pristine interlayer interfaces, thus limiting the layer-by-layer assembly method to small-scale proof-of-concept demonstrations. Here we report the generation of wafer-scale semiconductor films with a very high level of spatial uniformity and pristine interfaces. The vertical composition and properties of these films are designed at the atomic scale using layer-by-layer assembly of two-dimensional building blocks under vacuum. We fabricate several large-scale, high-quality heterostructure films and devices, including superlattice films with vertical compositions designed layer-by-layer, batch-fabricated tunnel device arrays with resistances that can be tuned over four orders of magnitude, band-engineered heterostructure tunnel diodes, and millimetre-scale ultrathin membranes and windows. The stacked films are detachable, suspendable and compatible with water or plastic surfaces, which will enable their integration with advanced optical and mechanical systems.

Subunit disassembly pathway of human hemoglobin revealing the site-specific role of its cysteine residues.

Cysteine residues play a unique role in human hemoglobin (Hb) by affecting its cooperative oxygen binding behavior and the stability of its tetrameric structure. However, how these cysteine residues fulfill their biophysical functions from the molecular level is yet unclear. Here we study the subunit disassembly pathway of human hemoglobin using the sulfhydryl reagent, p-hydroxymercuribenzoate (PMB) and investigate the functional roles of cysteine residues in human hemoglobin. We show evidence from the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry that all three types of cysteine residues, including the surface-exposed ßCys93 and the shielded αCys104 and ßCys112 are reactive to PMB, resolving an issue long under debate. It is demonstrated that all three types of cysteine residues must be blocked by PMB to accomplish the subunit disassembly, and the PMB-cysteine reactions proceed in a stepwise manner with an order of ßCys93, αCys104, and ßCys112. The PMB reactions with the three different cysteine residues demonstrate strong site-specificity. The possible influence of PMB-cysteine reactions to the stability of various intersubunit salt bridges has been discussed based on the crystallographic structure of hemoglobin, providing insights in understanding the hemoglobin subunit disassembly pathway and the site-specific functional role of each cysteine residue in hemoglobin.

Totally cystic schwannoma of the lumbar spine.

A schwannoma is a benign tumor arising from a schwann cell and occurs mainly in the nerve sheath in the intradural extramedullary region. Schwannomas have been well described as occurring in the lumbar spine, but total cystic degeneration of schwannomas is rarely reported. The authors describe the clinical and radiographic evaluations and treatment of a rare case of an intraextradural totally cystic schwannoma on the lumbar spine.Two patients reported a history of 6 to 12 months of pain accompanied by weakness in the lower extremities. On examination, 1 patient had bilateral lower-extremity muscle strength graded at 4/5, and magnetic resonance imaging revealed a cystic schwannoma (1.5 × 2.0 cm in the sagittal dimension) at L2-L3. The other patient had a right lower-extremity muscle strength graded at 3/5, and magnetic resonance imaging revealed a cystic schwannoma (2.0 × 3.0 cm in the sagittal dimension) at L4-L5. The patients underwent operative treatment, and the tumors were completely removed, as were the filum terminale adhered to the tumor. Pedicle screws were used to maintain stability of the lumbar spine. Gross examination of the tumors showed yellowish-white soft contents. Histologic examination confirmed that they were benign totally cystic schwannomas. Postoperatively, the patients' neurologic symptoms completely resolved.Cystic schwannomas can be diagnosed using preoperative magnetic resonance imaging. The filum terminale cut off the tumor walls did not cause the clinical symptoms in the 2 patients.

MRI study of the position of the conus medullaris in patients with lumbar spinal stenosis.

Substantial data exist from cadaveric and magnetic resonance imaging studies regarding the position of the conus medullaris in normally developed adults. However, no large studies have documented the position of the conus medullaris in patients with diagnosed lumbar spinal stenosis. To goal of the current study was to determine the position of the conus medullaris within a living adult population with existing pathology of lumbar spinal stenosis. In a retrospective study, 234 patients (110 women and 124 men; mean age, 48.8 years) with diagnosed lumbar spinal stenosis had their T2-weighted, midline, sagittal, spin-echo magnetic resonance imaging studies compared to assess and confirm the position of the conus medullaris. A straight line perpendicular to the long axis of the spinal cord in the median sagittal sequence was subtended to the adjacent vertebra or disk space, and the position was defined in relation to the vertebra or disk space. The conus medullaris position was labeled in relation to the upper, middle, and lower segments of the adjacent vertebral body or the adjacent disk space and assigned numerical values from 1 to 12. The position of the conus medullaris in patients with lumbar spinal stenosis followed a normal distribution. The mean conus medullaris position was mainly within the lower third of the L1 vertebral body (ranged from the middle third of T12 to the upper third of L3). No significant differences existed between men and women with lumbar spinal stenosis. The conus medullaris position was found to be unaffected by the pathology of lumbar spinal stenosis.

Screening of antibiotic susceptibility to ß-lactam-induced elongation of Gram-negative bacteria based on dielectrophoresis.

We demonstrate a rapid antibiotic susceptibility test (AST) based on the changes in dielectrophoretic (DEP) behaviors related to the ß-lactam-induced elongation of Gram-negative bacteria (GNB) on a quadruple electrode array (QEA). The minimum inhibitory concentration (MIC) can be determined within 2 h by observing the changes in the positive-DEP frequency (pdf) and cell length of GNB under the cefazolin (CEZ) treatment. Escherichia coli and Klebsiella pneumoniae and the CEZ are used as the sample bacteria and antibiotic respectively. The bacteria became filamentous due to the inhibition of cell wall synthesis and cell division and cell lysis occurred for the higher antibiotic dose. According to the results, the pdfs of wild type bacteria decrease to hundreds of kHz and the cell length is more than 10 µm when the bacterial growth is inhibited by the CEZ treatment. In addition, the growth of wild type bacteria and drug resistant bacteria differ significantly. There is an obvious decrease in the number of wild type bacteria but not in the number of drug resistant bacteria. Thus, the drug resistance of GNB to ß-lactam antibiotics can be rapidly assessed. Furthermore, the MIC determined using dielectrophoresis-based AST (d-AST) was consistent with the results of the broth dilution method. Utilizing this approach could reduce the time needed for bacteria growth from days to hours, help physicians to administer appropriate antibiotic dosages, and reduce the possibility of the occurrence of multidrug resistant (MDR) bacteria.