Observation of Josephson harmonics in tunnel junctions.

Approaches to developing large-scale superconducting quantum processors must cope with the numerous microscopic degrees of freedom that are ubiquitous in solid-state devices. State-of-the-art superconducting qubits employ aluminium oxide (AlOx) tunnel Josephson junctions as the sources of nonlinearity necessary to perform quantum operations. Analyses of these junctions typically assume an idealized, purely sinusoidal current-phase relation. However, this relation is expected to hold only in the limit of vanishingly low-transparency channels in the AlOx barrier. Here we show that the standard current-phase relation fails to accurately describe the energy spectra of transmon artificial atoms across various samples and laboratories. Instead, a mesoscopic model of tunnelling through an inhomogeneous AlOx barrier predicts percent-level contributions from higher Josephson harmonics. By including these in the transmon Hamiltonian, we obtain orders of magnitude better agreement between the computed and measured energy spectra. The presence and impact of Josephson harmonics has important implications for developing AlOx-based quantum technologies including quantum computers and parametric amplifiers. As an example, we show that engineered Josephson harmonics can reduce the charge dispersion and associated errors in transmon qubits by an order of magnitude while preserving their anharmonicity.

Left main coronary artery compression in precapillary pulmonary hypertension.

Pulmonary hypertension (PH) is a progressive and invalidating condition despite available therapy. Addressing complications such as left main coronary artery compression (LMCo) due to the dilated pulmonary artery (PA) may improve symptoms and survival. Nevertheless, clear recommendations are lacking. The aim of this study is to analyze the prevalence, characteristics, predictive factors and impact of LMCo in a heterogenous precapillary PH population in a single referral center. Two hundred sixty-five adults with various etiologies of precapillary PH at catheterization were reviewed. Coronary angiography (CA) was performed for LMCo suspicion. Revascularization was performed in selected cases. Outcomes were assessed at a mean follow-up of 3.9 years. LMCo was suspected in 125 patients and confirmed in 39 (31.2%), of whom 21 (16.8%) had 50%-90% stenoses. Nine revascularizations were performed, with clinical improvement. The only periprocedural complication was a stent migration. LMCo was associated with PH etiology (p 0.003), occuring more frequently in congenital heart disease-associated PH (61.5% of all LMCo cases, 66.6% of LMCo ≥ 50%). Predictors of LMCo ≥50% were PA ≥ 37.5 mm (Sn 81%, Sp 74%) and PA-to-aorta ≥1.24 (Sn 81%, Sp 69%), with increased discrimination when considering RV end-diastolic area. LMCo ≥ 50% without revascularization presented clinical deterioration and worse survival (p 0.019). This analysis of a heterogeneous pre-capillary PH population provides LMCo prevalence estimation, predictive factors (PA size, PA-to-aorta, RV end-diastolic area and PH etiology) and long-term impact. While LMCo impact on survival is inconclusive, untreated LMCo ≥ 50% has worse prognosis. LMCo revascularization may be performed safely and with good outcomes.

Left main coronary artery compression by dilated pulmonary artery in pulmonary arterial hypertension: a systematic review and meta-analysis.

OBJECTIVE: Pulmonary arterial hypertension (PAH) can lead to left main coronary artery compression (LMCo), but data on the impact, screening and treatment are limited. A meta-analysis of LMCo cases could fill the knowledge gaps in this topic. METHODS: Electronic databases were searched for all LMCo/PAH studies, abstracts and case reports including pulmonary artery (PA) size. Restricted maximum likelihood meta-analysis was used to evaluate LMCo-associated factors. Specificity, sensitivity and accuracy of PA size thresholds for diagnosis of LMCo were calculated. Treatment options and outcomes were summarized. RESULTS: A total of five case-control cohorts and 64 case reports/series (196 LMCo and 438 controls) were included. LMCo cases had higher PA diameter (Hedge's g 1.46 [1.09; 1.82]), PA/aorta ratio (Hedge's g 1.1 [0.64; 1.55]) and probability of CHD (log odds-ratio 1.22 [0.54; 1.9]) compared to non-LMCo, but not PA pressure or vascular resistance. A 40 mm cut-off for the PA diameter had balanced sensitivity (80.5%), specificity (79%) and accuracy (79.7%) for LMCo diagnosis, while a value of 44 mm had higher accuracy (81.7%), higher specificity (91.5%) but lower sensitivity (71.9%). Pooled mortality after non-conservative treatment (n = 150, predominantly stenting) was 2.7% at up to 22 months of mean follow-up, with 83% survivors having no angina at follow-up. CONCLUSION: PA diameter, PA/aorta ratio and CHD are associated with LMCo, while hemodynamic parameters are not. Data from this study support that a PA diameter cut-off between 40 and 44 mm can offer optimal accuracy for LMCo screening. Preferred treatment was coronary stenting, associated with low mid-term mortality and symptom relief. Diagnosis and management of left main coronary artery compression (LMCo) in patients with pulmonary arterial hypertension (PAH).

Carotid arterial stiffness is increased and related to left ventricular function in patients with hypertrophic cardiomyopathy.

AIMS: To assess the carotid mechanical properties in patients with hypertrophic cardiomyopathy and the relation between arterial stiffness and left ventricular function in this setting. METHODS AND RESULTS: We have prospectively enrolled 71 patients (52 ± 16 years, 34 men) with hypertrophic cardiomyopathy, divided into two groups depending on the presence (46 patients) or absence (25 patients) of cardiovascular risk factors associated with increased arterial stiffness. Twenty-five normal subjects similar by age and gender with hypertrophic cardiomyopathy patients without risk factors formed the control group. A comprehensive echocardiography was performed in all subjects. Carotid arterial stiffness index (ß index), pressure-strain elastic modulus, arterial compliance, and pulse wave velocity were also obtained using an echo-tracking system. ß index, pulse wave velocity, and pressure-strain elastic modulus were significantly higher in hypertrophic cardiomyopathy patients without risk factors compared to controls. After linear regression analysis, the increase in carotid ß index was independently correlated with the presence of hypertrophic cardiomyopathy [beta = 0.49, 95% confidence interval (CI) = 1.04-3.02; P < 0.001]. In the entire hypertrophic cardiomyopathy population arterial stiffness parameters correlated with age, gender, hypertension degree, presence of hypercholesterolaemia, and the E/e' ratio. In multivariable analysis, ß index (beta = 0.36, 95% CI = 0.32-1.25; P = 0.001), global left ventricular longitudinal strain, and the presence of left ventricular outflow tract obstruction were independently correlated with the E/e' ratio. CONCLUSION: In patients with hypertrophic cardiomyopathy arterial stiffness is increased independently of age or presence of cardiovascular risk factors. Carotid artery stiffness is independently related to left ventricular filling pressure, increased arterial stiffness representing a possible marker of a more severe phenotype.

Granular aluminium as a superconducting material for high-impedance quantum circuits.

Superconducting quantum information processing machines are predominantly based on microwave circuits with relatively low characteristic impedance, about 100 Ω, and small anharmonicity, which can limit their coherence and logic gate fidelity1,2. A promising alternative is circuits based on so-called superinductors3-6, with characteristic impedances exceeding the resistance quantum RQ = 6.4 kΩ. However, previous implementations of superinductors, consisting of mesoscopic Josephson junction arrays7,8, can introduce unintended nonlinearity or parasitic resonant modes in the qubit vicinity, degrading its coherence. Here, we present a fluxonium qubit design based on a granular aluminium superinductor strip9-11. We show that granular aluminium can form an effective junction array with high kinetic inductance and be in situ integrated with standard aluminium circuit processing. The measured qubit coherence time [Formula: see text] illustrates the potential of granular aluminium for applications ranging from protected qubit designs to quantum-limited amplifiers and detectors.

Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum.

Superconducting high kinetic inductance elements constitute a valuable resource for quantum circuit design and millimeter-wave detection. Granular aluminum (grAl) in the superconducting regime is a particularly interesting material since it has already shown a kinetic inductance in the range of nH/□ and its deposition is compatible with conventional Al/AlOx/Al Josephson junction fabrication. We characterize microwave resonators fabricated from grAl with a room temperature resistivity of 4×10^{3} µΩ cm, which is a factor of 3 below the superconductor to insulator transition, showing a kinetic inductance fraction close to unity. The measured internal quality factors are on the order of Q_{i}=10^{5} in the single photon regime, and we demonstrate that nonequilibrium quasiparticles (QPs) constitute the dominant loss mechanism. We extract QP relaxation times in the range of 1 s and we observe QP bursts every ∼20 s. The current level of coherence of grAl resonators makes them attractive for integration in quantum devices, while it also evidences the need to reduce the density of nonequilibrium QPs.

Romanian Registry of Hypertrophic Cardiomyopathy - overview of general characteristics and therapeutic choices at a national level.

INTRODUCTION: Hypertrophic cardiomyopathy (HCM) is a disease with increased left ventricular (LV) wall thickness not solely explained by abnormal loading conditions, with great heterogeneity regarding clinical expression and prognosis. The aim of the present study was to collect data on HCM patients from different centres across the country, in order to assess the general characteristics and therapeutic choices in this population. METHODS: Between December 2014 and April 2017, 210 patients from 11 Romanian Cardiology centres were enrolled in the National Registry of HCM. All patients had to fulfil the diagnosis criteria for HCM according to the European Society of Cardiology guidelines. Clinical, electrocardiographic, imaging and therapeutic characteristics were included in a predesigned online file. RESULTS: Median age at enrolment was 55 ± 15 years with male predominance (60%). 43.6% of the patients had obstructive HCM, 50% non-obstructive HCM, while 6.4% had an apical pattern. Maximal wall thickness was 20.3 ± 4.8 mm (limits 15-37 mm) while LV ejection fraction was 60 ± 8%. Heart failure symptoms dominated the clinical picture, mainly NYHA functional class II (51.4%). Most frequent arrhythmias were atrial fibrillation (28.1%) and non-sustained ventricular tachycardia (19.9%). Mean sudden cardiac death risk score (SCD-RS) was 3.0 ± 2.3%, with 10.4% of the patients with high risk of SCD. However, only 5.7% received an ICD. Patients were mainly treated with beta-blockers (72.9%), diuretics (28.1%) and oral anticoagulants (28.6%). Invasive treatment of LVOT obstruction was performed in a small number of patients: 22 received myomectomy and 13 septal ablation. Cardiac magnetic resonance was reported in only 14 patients (6.6%). CONCLUSIONS: The Romanian registry of HCM illustrates patient characteristics at a national level as well as the gaps in management which need improvement - accessibility to high-end diagnostic tests and invasive methods of treatment.

Standardization of 67Cu and calibration of the ionization chamber. Impurities and decay scheme problems.

This paper describes the standardization of 67Cu by the 4πß(PC)-γ coincidence method, and the calibration of ionization chamber. The difficulties were. (i) One of the excited levels of 67Zn has a half life of 9.10µs. (ii) A recent publication reconsiders the decay scheme parameters. (iii) The solution had a significant content of impurities. The conclusions were that the result of absolute standardization is less influenced by the decay scheme parameters and impurities than the measurements by ionization chamber.

Results of an international comparison of activity measurements of 68Ge.

An international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)ß-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11)kBqg-1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence.

Revascularization in a 17-Year-Old Girl with Neurofibromatosis and Severe Hypertension Caused by Renal Artery Stenosis.

Renal artery stenosis caused by neurofibromatosis is a rare cause of renovascular hypertension. This hypertension can develop during childhood and is one of the leading causes of poor outcome. We report the case of a 17-year-old girl who was incidentally diagnosed with severe hypertension. During her examination for secondary hypertension, we reached a diagnosis of neurofibromatosis type 1 on the basis of a cluster of typical findings: optic nerve glioma, café au lait spots, nodular neurofibromas, and axillary freckling. Renal angiograms revealed a hemodynamically significant left renal artery stenosis (70%). Renal angioplasty with a self-expanding stent was performed one month later for rapidly progressive renal artery stenosis (90%) and uncontrolled blood pressure. Excellent blood pressure control resulted immediately and was maintained as of the 2-year follow-up evaluation. We think that percutaneous transluminal renal angioplasty can be effective in select patients who have neurofibromatosis type 1 and refractory hypertension caused by renal artery stenosis.

A Congenital Gerbode Defect associated with a Rare Structural Abnormality of the Mitral Valve Diagnosed in an Adult Patient.

We report the case of a rare association of a congenital Gerbode defect with severe mitral regurgitation due to abnormal linear structure of mitral valve, diagnosed in an adult patient. The case highlights the importance of a thorough examination interpreting the echocardiographic findings on a pathophysiological basis. It also underlines the complementary role of different imaging techniques with transesophageal echocardiography, allowing the precise assessment of both structural and functional abnormalities in such a complex case. The patient underwent mitral valve replacement with a bileaflet mechanical prosthesis and repair of the Gerbode defect. The imaging findings were confirmed during the surgical procedure, leading to a good outcome.

Minimum Detectable Activity in gamma spectrometry and its use in low level activity measurements.

In this paper there are described three different algorithms of Minimum Detectable Activity (MDA) calculus, and its use in high resolution gamma spectrometry. In the first part, few introductive theoretical aspects related to the MDA are presented. Further, the theory was applied to real gamma rays spectrometry measurements and the results were compared with the activities reference values. Two different gamma spectrometry systems, both of them using High Purity Germanium (HPGe) detectors, but having different efficiencies, were used. Samples having different geometries and radionuclides content were measured. The measured samples were made by dissolving of some acids containing anthropogenic radionuclides in water, obtaining a density of 1g/cm(3). Choosing this type of matrix was done because of its high homogeneity.

Measurement of liquid scintillation sources of (210)Pb obtained from (222)Rn decay.

Liquid scintillation samples were filled with (222)Rn and the activity was measured with good precision after reaching the secular equilibrium with the progeny (218)Po, (214)Pb, (214)Bi and (214)Po. After decay of most of (222)Rn activity, the samples contain (210)Pb and progeny. The activities of (210)Pb and progeny can be calculated as a function of time using the initial (222)Rn activity. The samples were measured in a TDCR counter and the experimentally determined counting efficiencies are in accordance with previously published results.

A novel method for the activity measurement of large-area beta reference sources.

A novel method has been developed for the activity measurement of large-area beta reference sources. It makes use of two emission rate measurements and is based on the weak dependence between the source activity and the activity distribution for a given value of transmission coefficient. The method was checked experimentally by measuring the activity of two ((60)Co and (137)Cs) large-area reference sources constructed from anodized aluminum foils. Measurement results were compared with the activity values measured by gamma spectrometry. For each source, they agree within one standard uncertainty and also agree within the same limits with the certified values of the source activity.

Measurement of (124)I.

The paper describes the measurements performed at IFIN-HH regarding the creation of a Romanian (124)I standard, consisting of: absolute standardization of the solution by the application of the 4πß(PC)-γ coincidence method; Calibration of the CENTRONIC IG12/20A ionization chamber with a standardised solution and comparison with a calculated efficiency; γ-ray spectrometry activity measurement and determination of the impurity levels; Comparison of the results of the three methods.

A Congenital Gerbode Defect associated with a Rare Structural Abnormality of the Mitral Valve Diagnosed in an Adult Patient

We report the case of a rare association of a congenital Gerbode defect with severe mitral regurgitation due to abnormal linear structure of mitral valve, diagnosed in an adult patient. The case highlights the importance of a thorough examination interpreting the echocardiographic findings on a pathophysiological basis. It also underlines the complementary role of different imaging techniques with transesophageal echocardiography, allowing the precise assessment of both structural and functional abnormalities in such a complex case. The patient underwent mitral valve replacement with a bileaflet mechanical prosthesis and repair of the Gerbode defect. The imaging findings were confirmed during the surgical procedure, leading to a good outcome.

Shigeo Satomura: 60 years of Doppler ultrasound in medicine.

This year we celebrate 60 years since Shigeo Satomura published the first measurements of the Doppler shift of ultrasonic signals from a beating heart. He demonstrated that Doppler signals can be retrieved from heart movements when insonated with 3 MHz ultrasonic waves. Later, togheter with Ziro Kaneko, he constructed the first Doppler flowmeter to measure the blood flow velocities in peripheral and extracranial brain-supplying vessels using ultrasounds. They proved that ultrasonic Doppler signals from arteries and veins can be recorded from the surface of the skin and pioneered transcutaneous flow analysis in systole and diastole in both normal and diseased blood vessels. These were the first medical applications of Doppler sonography and impressive technologic innovations have been continuing ever since. Over time, Doppler techniques became a key player in diagnostic ultrasound for hemodynamic assessment, replacing cardiac catheterization in many clinical settings.

Right ventricular remodeling, its correlates, and its clinical impact in hypertrophic cardiomyopathy.

BACKGROUND: Structural right ventricular (RV) abnormalities are present in a substantial proportion of patients with hypertrophic cardiomyopathy (HCM), but the trigger for RV hypertrophy remains unclear. The aim of this study was to assess the relationship between RV and left ventricular (LV) remodeling and the impact of biventricular involvement on clinical status in this setting. METHODS: Ninety-nine patients with HCM and 30 normal subjects with a similar age and gender distribution were prospectively enrolled. Comprehensive echocardiography was performed in all, including the assessment of LV and RV function by tissue Doppler and speckle-tracking echocardiography. Measurement of RV free wall thickness (RVWT) was performed at end-diastole, in a zoomed subcostal view, focusing on the RV midwall. RESULTS: Patients with HCM had increased RVWT (6.4 ± 1.9 vs 3.6 ± 0.8 mm, P < .001) and lower values of RV global longitudinal strain (-19.4 ± 4.4% vs -23.8 ± 2.7%, P < .001) compared with control subjects. RVWT was independently related to LV mass and LV global longitudinal strain. Increased RVWT was correlated with New York Heart Association class (r = 0.20, P = .04) and calculated sudden cardiac death risk score (r = 0.52, P < .001) and was independently related to the presence of ventricular arrhythmias (odds ratio, 2.02; 95% CI, 1.28-3.19; P = .002). CONCLUSIONS: In patients with HCM, the presence of RV hypertrophy was associated with increased LV mass and reduced LV longitudinal strain, correlated with increased calculated sudden cardiac death risk score, and independently related to the presence of ventricular arrhythmias. These data suggest more severe disease in patients with biventricular HCM.

Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles.

Owing to the low-loss propagation of electromagnetic signals in superconductors, Josephson junctions constitute ideal building blocks for quantum memories, amplifiers, detectors and high-speed processing units, operating over a wide band of microwave frequencies. Nevertheless, although transport in superconducting wires is perfectly lossless for direct current, transport of radio-frequency signals can be dissipative in the presence of quasiparticle excitations above the superconducting gap. Moreover, the exact mechanism of this dissipation in Josephson junctions has never been fully resolved experimentally. In particular, Josephson's key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is π (ref. 2) has never been observed. This subtle effect can be understood as resulting from the destructive interference of two separate dissipative channels involving electron-like and hole-like quasiparticles. Here we report the experimental observation of this quantum coherent suppression of quasiparticle dissipation across a Josephson junction. As the average phase bias across the junction is swept through π, we measure an increase of more than one order of magnitude in the energy relaxation time of a superconducting artificial atom. This striking suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits.

Boundary layer flow past a stretching surface in a porous medium saturated by a nanofluid: Brinkman-Forchheimer model.

In this study, the steady forced convection flow and heat transfer due to an impermeable stretching surface in a porous medium saturated with a nanofluid are investigated numerically. The Brinkman-Forchheimer model is used for the momentum equations (porous medium), whereas, Bongiorno's model is used for the nanofluid. Uniform temperature and nanofluid volume fraction are assumed at the surface. The boundary layer equations are transformed to ordinary differential equations in terms of the governing parameters including Prandtl and Lewis numbers, viscosity ratio, porous medium, Brownian motion and thermophoresis parameters. Numerical results for the velocity, temperature and concentration profiles, as well as for the reduced Nusselt and Sherwood numbers are obtained and presented graphically.