Nonvolatile memory with molecule-engineered tunneling barriers

We report a novel field-sensitive tunneling barrier by embedding C60 in SiO2 for nonvolatile memory applications. C60 is a better choice than ultra-small nanocrystals due to its monodispersion. Moreover, C60 provides accessible energy levels to prompt resonant tunneling through SiO2 at high fields. However, this process is quenched at low fields due to HOMO-LUMO gap and large charging energy of C60. Furthermore, we demonstrate an improvement of more than an order of magnitude in retention to program/erase time ratio for a metal nanocrystal memory. This shows promise of engineering tunnel dielectrics by integrating molecules in the future hybrid molecular-silicon electronics.Comment: to appear in Applied Physics Letter

Quantum delayed-choice experiment with a beam splitter in a quantum superposition

A quantum system can behave as a wave or as a particle, depending on the experimental arrangement. When for example measuring a photon using a Mach-Zehnder interferometer, the photon acts as a wave if the second beam-splitter is inserted, but as a particle if this beam-splitter is omitted. The decision of whether or not to insert this beam-splitter can be made after the photon has entered the interferometer, as in Wheeler's famous delayed-choice thought experiment. In recent quantum versions of this experiment, this decision is controlled by a quantum ancilla, while the beam splitter is itself still a classical object. Here we propose and realize a variant of the quantum delayed-choice experiment. We configure a superconducting quantum circuit as a Ramsey interferometer, where the element that acts as the first beam-splitter can be put in a quantum superposition of its active and inactive states, as verified by the negative values of its Wigner function. We show that this enables the wave and particle aspects of the system to be observed with a single setup, without involving an ancilla that is not itself a part of the interferometer. We also study the transition of this quantum beam-splitter from a quantum to a classical object due to decoherence, as observed by monitoring the interferometer output.Comment: 9 pages, 7 figures, Accepted by Physical Review Letter

Reversing flow in microchannel evaporations

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.The paper presents the phenomenon of periodically reversing flow in a microchannel evaporators used in air conditioning systems which will be illustrated with high speed videos in the presentation. These evaporators have multiple parallel channels between 0.5 and 1mm and headers (manifolds) that have to accommodate tubes of typically 15 to 25 mm major (width). A simultaneous flow visualizations and pressure measurements confirmed the periodic flow reversal and associated fluctuations. The oscillatory behavior of the flow is linked and related with oscillations of the evaporator pressure in the inlet header and the pressure drop. Visualization of the flow in headers and tubes will be presented. Paper will present experiments that have revealed significant ratio of reversed vapor flow – in the range of 3-7% of the mail flow, in addition to liquid that is reversed alongside. The magnitude and frequency of oscillations are directly proportional to heat flux. Three potential impacts of flow reversal on evaporator performance are discussed: 1) moderate liquid maldistribution; 2) reduced heat transfer; 3) increased refrigerant side pressure drop. Finally, to mitigate impacts of periodic reverse flow, a solution is proposed: to vent and bypass backflow vapor accumulated in the inlet header.am201

Lithospheric Structure Underneath the Archean Tanzania Craton and Adjacent Regions from a Joint Inversion of Receiver Functions and Rayleigh-Wave Phase Velocity Dispersion

Lithospheric structure beneath the Archean Tanzania craton and adjacent regions, including segments of the East African rift system (EARS) and the Proterozoic-early Paleozoic orogenic belts between the EARS and the craton, is imaged by a joint inversion of receiver functions and Rayleigh wave dispersion measurements derived from ambient seismic noise for shorter periods and teleseismic data for longer periods. Our resulting crustal thickness, crustal VP= VS measurements and 3D shear-wave velocity model for the upper 120 km show a clear spatial correspondence with major surficial geological features. The new results suggest the presence of a mafic layer in the bottom of the crust of the entire Archean craton, which is previously only identified beneath the southern portion of the craton. High crustal VP= VS values measured in the Rungwe Volcanic Province and most areas of the Kenya and Tanganyika rift segments can be attributed to a combined result of basaltic sediments atop the crust, magmatic intrusion, and crustal partial melting. The Kivu Volcanic Province and parts of the Kenya rift segment are characterized by localized lower-than-normal crustal VP= VS values and shear velocities in the lower crust and uppermost mantle, which, given the presence of large volume of CO2 from surficial observations, can be best interpreted by CO2-filled fractures or conduits. Lower-than-normal shear velocities in the uppermost mantle are revealed beneath almost the entire study region with the lowest values found in all the three volcanic provinces. The lowvelocities are indicative of an underplated layer formed by mantle-derived magmatic materials trapped below the Moho. The relatively low velocities beneath the volcanic provinces might be caused by a higher degree of partial melting in the uppermost mantle

Prenatal diagnosis of total and partial anomalous pulmonary venous connection: multicenter cohort study and meta-analysis

Objectives: The aims of this study were to review systematically literature on and describe the sonographic features and associated anomalies of total (TAPVC) and partial (PAPVC) anomalous pulmonary venous connection and scimitar syndrome (SS). Methods: A retrospective cohort study was carried out of cases of TAPVC, PAPVC and SS that underwent comprehensive ultrasound examination, seen over a 20-year period at two tertiary referral centers. Assessed variables included TAPVC subtype, gestational age at diagnosis, area behind the left atrium, ventricular disproportion, vertical vein, pulmonary venous obstruction, mode of diagnosis, association with cardiac and extracardiac conditions, and pregnancy and fetoneonatal outcomes. The outcome was considered favorable if the individual was alive and well (no functional impairment from surgery or cardiac or extracardiac conditions). Cases associated with right isomerism were excluded from the analysis, as TAPVC in these cases was only one of several major cardiac anomalies affecting sonographic signs. A systematic review was performed in order to obtain a synthesis of characteristics associated with TAPVC, PAPVC and SS. The literature search of PubMed and EMBASE (1970–2016) included reviews, case series and case reports. A meta-analysis was conducted only for TAPVC. Random-effects models were used to obtain pooled estimates of the frequencies of clinical characteristics and sonographic features. Results: For TAPVC, a total of 15 studies involving 71 patients (including 13 from the current cohort study) were included in the systematic review and meta-analysis. The pooled estimate for the association of TAPVC with congenital heart disease was 28.3% (95% CI, 18.1–41.3%) and with extracardiac anomalies it was 18.5% (95% CI, 10.5–30.6%). Of TAPVC cases, obstructed venous return was observed in 34.1% (95% CI, 22.7–47.7%), a favorable outcome in 43.8% (95% CI, 24.0–65.8%), ventricular disproportion in 59.2% (95% CI, 45.1–72.0%), increased area behind the left atrium in 58.1% (95% CI, 41.1–73.5%) and a vertical vein in 59.3% (95% CI, 41.1–75.3%). Diagnosis was established by using color or power Doppler in 84.9% (95% CI, 67.3–93.9%) of cases. For SS, there were only three studies describing eight cases, to which the current study added another five. Ventricular disproportion was present in three out of nine SS cases for which data were available, but for two of these, there was a concurrent heart anomaly. Color Doppler was used for all SS diagnoses, and four-dimensional echocardiography was useful in two out of six cases in which it was used. Outcome for SS cases was generally good. For PAPVC, there were only five studies describing five cases, to which the current study added another two. Major cardiac anomalies were associated in four out of seven of these cases, and extracardiac anomalies in three out of six cases for which data were available. Conclusions: TAPVC can be associated with other cardiac and extracardiac anomalies in a significant percentage of cases. Leading sonographic signs are ventricular disproportion, increased area behind the left atrium and the finding of a vertical vein. Color/power Doppler is the key mode for diagnosis of TAPVC. Obstructed venous return can be expected in roughly one-third of cases of TAPVC and outcome is favorable in less than half of cases. Data for SS and PAPVC are too few to synthesize. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd

Association of Mineralocorticoid Receptor Antagonists With the Mortality and Cardiovascular Effects in Dialysis Patients: A Meta-analysis

Whether Mineralocorticoid receptor antagonists (MRA) reduce mortality and cardiovascular effects of dialysis patients remains unclear. A meta-analysis was designed to investigate whether MRA reduce mortality and cardiovascular effects of dialysis patients, with a registration in INPLASY (INPLASY2020120143). The meta-analysis revealed that MRA significantly reduced all-cause mortality (ACM) and cardiovascular mortality (CVM). Patients receiving MRA presented improved left ventricular mass index (LVMI) and left ventricular ejection fraction (LVEF), decreased systolic blood pressure (SBP) and diastolic blood pressure (DBP). There was no significant difference in the serum potassium level between the MRA group and the placebo group. MRA vs. control exerts definite survival and cardiovascular benefits in dialysis patients, including reducing all-cause mortality and cardiovascular mortality, LVMI, and arterial blood pressure, and improving LVEF. In terms of safety, MRA did not increase serum potassium levels for dialysis patients with safety. Systematic Review Registration: (https://inplasy.com/inplasy-protocol-1239-2/), identifier (INPLASY2020120143)

De novo design of a transmembrane Zn²⁺-transporting four-helix bundle.

The design of functional membrane proteins from first principles represents a grand challenge in chemistry and structural biology. Here, we report the design of a membrane-spanning, four-helical bundle that transports first-row transition metal ions Zn(2+) and Co(2+), but not Ca(2+), across membranes. The conduction path was designed to contain two di-metal binding sites that bind with negative cooperativity. X-ray crystallography and solid-state and solution nuclear magnetic resonance indicate that the overall helical bundle is formed from two tightly interacting pairs of helices, which form individual domains that interact weakly along a more dynamic interface. Vesicle flux experiments show that as Zn(2+) ions diffuse down their concentration gradients, protons are antiported. These experiments illustrate the feasibility of designing membrane proteins with predefined structural and dynamic properties