Ductus Arteriosus Stenting in Newborns - Transcatheter Approach as a Bridge Therapy for Corrective Surgery.

Duct-dependent congenital heart disease requires attentive therapeutic management since the only source of pulmonary blood flow in newborns is provided by the patent ductus arteriosus. The patency of the duct is the main objective in the first hours of life and it is guaranteed by prostaglandin E1 infusion, but it is not a long-term solution for this type of cardiac malformation. In order to augment pulmonary blood, there are two types of interventions that can be performed: a classical surgical shunt or stenting of the ductus arteriosus, a fairly new alternative to cardiac palliative surgery. Case selection for this type of procedure is essential regarding the patients' outcome. We present the management of a newborn diagnosed with (pseudo)atretic pulmonary valve, large ventricular septal defect and patent ductus arteriosus, who underwent an interventional procedure to secure pulmonary blood flow by placing a drug-eluting stent in the ductus arteriosus. The patient's evolution was not uneventful, several complications appeared, but after three months of neonatal intensive care we were able to discharge him in good clinical condition.

Computer vision AC-STEM automated image analysis for 2D nanopore applications.

Transmission electron microscopy (TEM) has led to important discoveries in atomic imaging and as an atom-by-atom fabrication tool. Using electron beams, atomic structures can be patterned, annealed and crystallized, and nanopores can be drilled in thin membranes. We review current progress in TEM analysis and implement a computer vision nanopore-detection algorithm that achieves a 96% pixelwise precision in TEM images of nanopores in 2D membranes (WS2), and discuss parameter optimization including a variation on the traditional grid search and gradient ascent. Such nanopores have applications in ion detection, water filtration, and DNA sequencing, where ionic conductance through the pore should be concordant with its TEM-measured size. Standard computer vision methods have their advantages as they are intuitive and do not require extensive training data. For completeness, we briefly comment on related machine learning for 2D materials analysis and discuss relevant progress in these fields. Image analysis alongside TEM allows correlated fabrication and analysis done simultaneously in situ to engineer devices at the atomic scale.

Intrinsic Properties of Suspended MoS2 on SiO2/Si Pillar Arrays for Nanomechanics and Optics.

Semiconducting two-dimensional (2D) materials, such as transition-metal dichalcogenides (TMDs), are emerging in nanomechanics, optoelectronics, and thermal transport. In each of these fields, perfect control over 2D material properties including strain, doping, and heating is necessary, especially on the nanoscale. Here, we study clean devices consisting of membranes of single-layer MoS2 suspended on pillar arrays. Using Raman and photoluminescence spectroscopy, we have been able to extract, separate, and simulate the different contributions on the nanoscale and to correlate these to the pillar array design. This control has been used to design a periodic MoS2 mechanical membrane with a high reproducibility and to perform optomechanical measurements on arrays of similar resonators with a high-quality factor of 600 at ambient temperature, hence opening the way to multiresonator applications with 2D materials. At the same time, this study constitutes a reference for the future development of well-controlled optical emissions within 2D materials on periodic arrays with reproducible behavior. We measured a strong reduction of the MoS2 band gap induced by the strain generated from the pillars. A transition from direct to indirect band gap was observed in isolated tent structures made of MoS2 and pinched by a pillar. In fully suspended devices, simulations were performed allowing both the extraction of the thermal conductance and doping of the layer. Using the correlation between the influences of strain and doping on the MoS2 Raman spectrum, we have developed a simple, elegant method to extract the local strain in suspended and nonsuspended parts of a membrane. This opens the way to experimenting with tunable coupling between light emission and vibration.

A Randomized Controlled Trial of Two Ready-to-Use Supplementary Foods Demonstrates Benefit of the Higher Dairy Supplement for Reduced Wasting in Mothers, and Differential Impact in Infants and Children Associated With Maternal Supplement Response.

BACKGROUND: There is no consensus over best approaches to reliably prevent malnutrition in rural communities in low-income countries. OBJECTIVE: We compared the effectiveness of 2 lipid-based ready-to-use supplementary foods (RUSFs) differing in dairy protein content to improve the nutritional status of mothers and at-risk infants and young children in rural Guinea-Bissau. METHODS: A 3-month cluster-randomized controlled pilot trial of 2 RUSFs was conducted with 692 mothers and 580 mildly or moderately malnourished infants (6-23 months) and children (24-59 months) from 13 villages. The RUSFs contained either 478 (mothers, children) or 239 kcal/d (infants) with 15% or 33% of protein from dairy and were distributed at community health centers 5 d/wk. Controls were wait-listed to receive RUSF. Primary outcomes were mid-upper arm circumference (MUAC) in mothers, and weight-for-age and height-for-age z-scores (WAZ and HAZ) in infants and children. RESULTS: There was a significant effect of the RUSF-33% on MUAC in mothers ( P = .03). The WAZ and HAZ increased substantially, by ≈1 z-score, in infants and children ( P < .01) independent of group randomization. In children, but not infants, baseline WAZ and change in maternal MUAC were associated with change in WAZ (ß = .07, P = .02). CONCLUSION: Ready-to-use supplementary foods with higher dairy protein content had a significant benefit in village mothers, supporting a comparable recent finding in preschool children. In addition, supplementation of children <2 years resulted in improved growth independent of family nutritional status, whereas success in older children was associated with change in maternal nutrition, suggesting the need for community-level education about preventing malnutrition in older, as well as younger, children.

Tunable Doping in Hydrogenated Single Layered Molybdenum Disulfide.

Structural defects in the molybdenum disulfide (MoS2) monolayer are widely known for strongly altering its properties. Therefore, a deep understanding of these structural defects and how they affect MoS2 electronic properties is of fundamental importance. Here, we report on the incorporation of atomic hydrogen in monolayered MoS2 to tune its structural defects. We demonstrate that the electronic properties of single layer MoS2 can be tuned from the intrinsic electron (n) to hole (p) doping via controlled exposure to atomic hydrogen at room temperature. Moreover, this hydrogenation process represents a viable technique to completely saturate the sulfur vacancies present in the MoS2 flakes. The successful incorporation of hydrogen in MoS2 leads to the modification of the electronic properties as evidenced by high resolution X-ray photoemission spectroscopy and density functional theory calculations. Micro-Raman spectroscopy and angle resolved photoemission spectroscopy measurements show the high quality of the hydrogenated MoS2 confirming the efficiency of our hydrogenation process. These results demonstrate that the MoS2 hydrogenation could be a significant and efficient way to achieve tunable doping of transition metal dichalcogenides (TMD) materials with non-TMD elements.

Band Alignment and Minigaps in Monolayer MoS2-Graphene van der Waals Heterostructures.

Two-dimensional layered MoS2 shows great potential for nanoelectronic and optoelectronic devices due to its high photosensitivity, which is the result of its indirect to direct band gap transition when the bulk dimension is reduced to a single monolayer. Here, we present an exhaustive study of the band alignment and relativistic properties of a van der Waals heterostructure formed between single layers of MoS2 and graphene. A sharp, high-quality MoS2-graphene interface was obtained and characterized by micro-Raman spectroscopy, high-resolution X-ray photoemission spectroscopy (HRXPS), and scanning high-resolution transmission electron microscopy (STEM/HRTEM). Moreover, direct band structure determination of the MoS2/graphene van der Waals heterostructure monolayer was carried out using angle-resolved photoemission spectroscopy (ARPES), shedding light on essential features such as doping, Fermi velocity, hybridization, and band-offset of the low energy electronic dynamics found at the interface. We show that, close to the Fermi level, graphene exhibits a robust, almost perfect, gapless, and n-doped Dirac cone and no significant charge transfer doping is detected from MoS2 to graphene. However, modification of the graphene band structure occurs at rather larger binding energies, as the opening of several miniband-gaps is observed. These miniband-gaps resulting from the overlay of MoS2 and the graphene layer lattice impose a superperiodic potential.

Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures.

Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.

Raman Shifts in Electron-Irradiated Monolayer MoS2.

We report how the presence of electron-beam-induced sulfur vacancies affects first-order Raman modes and correlate the effects with the evolution of the in situ transmission-electron microscopy two-terminal conductivity of monolayer MoS2 under electron irradiation. We observe a red-shift in the E' Raman peak and a less pronounced blue-shift in the A'1 peak with increasing electron dose. Using energy-dispersive X-ray spectroscopy and selected-area electron diffraction, we show that irradiation causes partial removal of sulfur and correlate the dependence of the Raman peak shifts with S vacancy density (a few %). This allows us to quantitatively correlate the frequency shifts with vacancy concentration, as rationalized by first-principles density functional theory calculations. In situ device current measurements show an exponential decrease in channel current upon irradiation. Our analysis demonstrates that the observed frequency shifts are intrinsic properties of the defective systems and that Raman spectroscopy can be used as a quantitative diagnostic tool to characterize MoS2-based transport channels.

A Randomized Controlled Trial Offering Higher- Compared with Lower-Dairy Second Meals Daily in Preschools in Guinea-Bissau Demonstrates an Attendance-Dependent Increase in Weight Gain for Both Meal Types and an Increase in Mid-Upper Arm Circumference for the Higher-Dairy Meal.

BACKGROUND: Controversy remains over the most effective approaches to prevent childhood malnutrition. OBJECTIVES: We tested the feasibility and effectiveness of delivering ready-to-use supplementary foods (RUSFs) as a second daily meal in preschool children aged 3-5 y in Guinea-Bissau, and compared RUSFs with different levels of dairy protein. METHODS: This study was a 3 mo cluster-randomized controlled pilot trial of 2 RUSFs differing in dairy protein in 533 boys and girls from 9 preschools. Children receiving RUSFs were compared with wait-listed controls, and all students received a daily school lunch. The RUSFs were delivered 5 d/wk for 3 mo and contained 478 kcal and 11.5 g protein per 92-g daily serving. Deliveries included a ready-to-use supplementary food with 15% of protein from dairy sources (RUSF-15%) or one with 33% of protein from dairy sources (RUSF-33%). Intention-to-treat (ITT) and per-protocol analyses (>50 d of RUSF consumption) were conducted. Changes in the weight-for-age z score (WAZ) and height-for-age z score were primary outcomes. Additional outcomes included changes in mid-upper arm circumference (MUAC), hemoglobin, and retinol binding protein. RESULTS: Baseline anthropometry was not different between groups (WAZ, -0.48 ± 1.04) and increased significantly over time (P < 0.01) with no effects of the RUSFs in ITT analyses. However, children consuming RUSFs for >50 d had a significantly greater increase in WAZ relative to the increase in controls (+0.40 and +0.32 for RUSF-15% and RUSF-33%, respectively, compared with +0.24 in controls, P < 0.01 and P < 0.05, respectively). RUSF-33%, but not RUSF-15%, also eliminated a decrease in MUAC observed in controls (-0.01 cm in RUSF-33% compared with -0.34 cm in controls, P < 0.05). The only difference between RUSF-15% and RUSF-33% was a mean decrease in hemoglobin in children receiving RUSF-15% (-0.5 compared with -0.002 g/dL, P = 0.05). CONCLUSIONS: Implementation of 2-meal preschool feeding programs is feasible in low-income countries, and there are measurable benefits relative to 1-meal programs in children attending preschool regularly. In addition, MUAC and hemoglobin measurements indicate that meals with 33% compared with 15% of protein from dairy may help prevent wasting and anemia.

Suspended Solid-state Membranes on Glass Chips with Sub 1-pF Capacitance for Biomolecule Sensing Applications.

Solid-state membranes are finding use in many applications in nanoelectronics and nanomedicine, from single molecule sensors to water filtration, and yet many of their electronics applications are limited by the relatively high current noise and low bandwidth stemming from the relatively high capacitance (>10 pF) of the membrane chips. To address this problem, we devised an integrated fabrication process to grow and define circular silicon nitride membranes on glass chips that successfully lower the chip capacitance to below 1 pF. We use these devices to demonstrate low-noise, high-bandwidth DNA translocation measurements. We also make use of this versatile, low-capacitance platform to suspend other thin, two-dimensional membrane such as graphene.

Cross-Talk Between Ionic and Nanoribbon Current Signals in Graphene Nanoribbon-Nanopore Sensors for Single-Molecule Detection.

Nanopores are now being used not only as an ionic current sensor but also as a means to localize molecules near alternative sensors with higher sensitivity and/or selectivity. One example is a solid-state nanopore embedded in a graphene nanoribbon (GNR) transistor. Such a device possesses the high conductivity needed for higher bandwidth measurements and, because of its single-atomic-layer thickness, can improve the spatial resolution of the measurement. Here measurements of ionic current through the nanopore are shown during double-stranded DNA (dsDNA) translocation, along with the simultaneous response of the neighboring GNR due to changes in the surrounding electric potential. Cross-talk originating from capacitive coupling between the two measurement channels is observed, resulting in a transient response in the GNR during DNA translocation; however, a modulation in device conductivity is not observed via an electric-field-effect response during DNA translocation. A field-effect response would scale with GNR source-drain voltage (Vds), whereas the capacitive coupling does not scale with Vds . In order to take advantage of the high bandwidth potential of such sensors, the field-effect response must be enhanced. Potential field calculations are presented to outline a phase diagram for detection within the device parameter space, charting a roadmap for future optimization of such devices.

Improving signal-to-noise performance for DNA translocation in solid-state nanopores at MHz bandwidths.

DNA sequencing using solid-state nanopores is, in part, impeded by the relatively high noise and low bandwidth of the current state-of-the-art translocation measurements. In this Letter, we measure the ion current noise through sub 10 nm thick Si3N4 nanopores at bandwidths up to 1 MHz. At these bandwidths, the input-referred current noise is dominated by the amplifier's voltage noise acting across the total capacitance at the amplifier input. By reducing the nanopore chip capacitance to the 1-5 pF range by adding thick insulating layers to the chip surface, we are able to transition to a regime in which input-referred current noise (∼ 117-150 pArms at 1 MHz in 1 M KCl solution) is dominated by the effects of the input capacitance of the amplifier itself. The signal-to-noise ratios (SNRs) reported here range from 15 to 20 at 1 MHz for dsDNA translocations through nanopores with diameters from 4 to 8 nm with applied voltages from 200 to 800 mV. Further advances in bandwidth and SNR will require new amplifier designs that reduce both input capacitance and input-referred amplifier noise.

Toward sensitive graphene nanoribbon-nanopore devices by preventing electron beam-induced damage.

Graphene-based nanopore devices are promising candidates for next-generation DNA sequencing. Here we fabricated graphene nanoribbon-nanopore (GNR-NP) sensors for DNA detection. Nanopores with diameters in the range 2-10 nm were formed at the edge or in the center of graphene nanoribbons (GNRs), with widths between 20 and 250 nm and lengths of 600 nm, on 40 nm thick silicon nitride (SiN(x)) membranes. GNR conductance was monitored in situ during electron irradiation-induced nanopore formation inside a transmission electron microscope (TEM) operating at 200 kV. We show that GNR resistance increases linearly with electron dose and that GNR conductance and mobility decrease by a factor of 10 or more when GNRs are imaged at relatively high magnification with a broad beam prior to making a nanopore. By operating the TEM in scanning TEM (STEM) mode, in which the position of the converged electron beam can be controlled with high spatial precision via automated feedback, we were able to prevent electron beam-induced damage and make nanopores in highly conducting GNR sensors. This method minimizes the exposure of the GNRs to the beam before and during nanopore formation. The resulting GNRs with unchanged resistances after nanopore formation can sustain microampere currents at low voltages (∼50 mV) in buffered electrolyte solution and exhibit high sensitivity, with a large relative change of resistance upon changes of gate voltage, similar to pristine GNRs without nanopores.

Differentiation of short, single-stranded DNA homopolymers in solid-state nanopores.

In the last two decades, new techniques that monitor ionic current modulations as single molecules pass through a nanoscale pore have enabled numerous single-molecule studies. While biological nanopores have recently shown the ability to resolve single nucleotides within individual DNA molecules, similar developments with solid-state nanopores have lagged, due to challenges both in fabricating stable nanopores of similar dimensions as biological nanopores and in achieving sufficiently low-noise and high-bandwidth recordings. Here we show that small silicon nitride nanopores (0.8- to 2-nm diameter in 5- to 8-nm-thick membranes) can resolve differences between ionic current signals produced by short (30 base) ssDNA homopolymers (poly(dA), poly(dC), poly(dT)), when combined with measurement electronics that allow a signal-to-noise ratio of better than 10 to be achieved at 1-MHz bandwidth. While identifying intramolecular DNA sequences with silicon nitride nanopores will require further improvements in nanopore sensitivity and noise levels, homopolymer differentiation represents an important milestone in the development of solid-state nanopores.