Potassium doping of vertically aligned multi-walled carbon nanotubes.

Alkali metal doping of multi-walled carbon nanotubes is of great interest, both fundamentally to explore the effect of dopants on quasi-one-dimensional electrical systems and for energy applications such as alkali metal storage. We present an investigation with complementary photoemission and Raman spectroscopies, fully carried out in an ultra-high vacuum, to unveil the electronic and vibrational response of a forest of highly aligned multi-walled carbon nanotubes by in situ potassium doping. The charge donation by the alkali adatoms induces a plasmon mode, and the density of states undergoes an energy shift consistent with electron donation and band filling of the multi-walled carbon nanotube band structure. The π-states in the valence band and the Raman peaks unveil an evolution that can be ascribed to charge donation and partially to a tensile strain exerted by the K adatoms on the carbon lattice. All these effects are thermally reversible, fostering these materials as a potential system for electronic charge harvesting.

Tuning the Electronic Response of Metallic Graphene by Potassium Doping.

Electron doping of graphene has been extensively studied on graphene-supported surfaces, where the metallicity is influenced by the substrate. Herewith we propose potassium adsorption on free-standing nanoporous graphene, thus eluding any effect due to the substrate. We monitor the electron migration in the π* downward-shifted conduction band. In this rigid band shift, we correlate the spectral density of the π* state in the upper Dirac cone with the associated plasmon, blue-shifted with increasing K dose, as deduced by electron energy loss spectroscopy. These results are confirmed by the Dirac plasmon activated by the C 1s emitted electrons, thanks to spatially resolved photoemission. This crosscheck constitutes a reference on the correlation between the electronic π* states in the conduction band and the Dirac plasmon evolution upon in situ electron doping of fully free-standing graphene.

Room-temperature synthesis of 2D-Ti3C2Tx nano-sheets by organic base treatment.

The growing demand for improved electrochemical performance in energy storage systems has stimulated research into advanced two-dimensional (2D) materials for electrodes. In this work, we obtain a layered MXene compound by exfoliating a titanium aluminum carbide precursor using tetramethylammonium hydroxide (TMAOH) ions in a full room temperature process followed by manual shaking. The hexagonal crystal structure and composition of the layered materials are characterized using different techniques. X-Ray diffraction shows the formation of 2D nano-sheets before and after the TMAOH treatment via its characteristic (002) diffraction peak, bringing to light an increase in the interlayer spacing after treatment. Scanning electron microscopy images confirm the layered morphology, whose composition is determined by energy dispersive x-ray analysis for the bulk material and by x-ray photoelectron spectroscopy for the surface of the obtained compounds. This study demonstrates a promising route to enhance delamination of this MXene 2D material in a low-cost room-temperature approach.

Gap Opening in Double-Sided Highly Hydrogenated Free-Standing Graphene.

Conversion of free-standing graphene into pure graphane─where each C atom is sp3 bound to a hydrogen atom─has not been achieved so far, in spite of numerous experimental attempts. Here, we obtain an unprecedented level of hydrogenation (≈90% of sp3 bonds) by exposing fully free-standing nanoporous samples─constituted by a single to a few veils of smoothly rippled graphene─to atomic hydrogen in ultrahigh vacuum. Such a controlled hydrogenation of high-quality and high-specific-area samples converts the original conductive graphene into a wide gap semiconductor, with the valence band maximum (VBM) ∼ 3.5 eV below the Fermi level, as monitored by photoemission spectromicroscopy and confirmed by theoretical predictions. In fact, the calculated band structure unequivocally identifies the achievement of a stable, double-sided fully hydrogenated configuration, with gap opening and no trace of π states, in excellent agreement with the experimental results.

Preliminary Air Quality and Microclimatic Conditions Study in the Santuario della Beata Vergine dei Miracoli in Saronno (VA).

In the present work, the microclimatic conditions (temperature (T), relative humidity (RH), and illuminance (I)), together with the air quality (both aerosol particulate matter (PM) and gaseous pollutants), were monitored to evaluate the environmental conditions inside the Santuario della Beata Vergine dei Miracoli in Saronno (VA), a masterpiece of the Italian Renaissance. For this purpose, dataloggers were used to carry out the T, RH, and I measurements, whereas an optical particle counter (OPC) was employed to perform the particle count and determine the concentration of the aerosol PM. Finally, diffusive passive samplers were used to determine the concentration of nitrogen dioxide (NO2) and BTEX (benzene, toluene, ethylbenzene, and xylenes). To identify possible spatial variations, the studies were conducted at different sites and different heights in the Sanctuary. Particular focus was given to the Easter week during which liturgical services attracting large numbers of people were carried out. Additionally, a comparison with the outdoor values was performed to highlight the accumulation phenomena and other variations in the concentrations of the species. Despite the indoor concentrations of pollutants and variations in the thermohygrometric parameters being generally lower compared to the outdoors (e.g., 5.2-15.0 µg m-3 versus 17.7-45.3 µg m-3 for NO2), the microclimatic conditions were often not in line with the Italian legislation and technical standards.

Impact of concomitant cardiac valvular surgery during implantation of continuous-flow left ventricular assist devices: A European registry for patients with mechanical circulatory support (EUROMACS) analysis.

BACKGROUND: We investigated the clinical outcomes after cardiac valvular surgery procedures concomitant (CCPs) with left ventricular assist device (LVAD) implantation compared to propensity score (PS) matched controls using the European Registry for Patients with Mechanical Circulatory Support (EUROMACS) data. METHODS: Between 2006 and 2018, 2760 continuous-flow LVAD patients were identified. Of these, 533 underwent a CCP during the LVAD implant. RESULTS: Cardiopulmonary bypass time (p < 0.001) and time for implant (p < 0.001) were both significantly longer in the LVAD+CCP group. Hospital mortality was comparable between the two groups from the unmatched population (15.7% vs. 14.1%, p = 0.073). Similarly, short-to-mid-term survival was similar in both groups, with 1-year, 3-year, and 5-year survival rates of 67.9%, 48.2%, and 27.7% versus 66.4%, 46.1%, and 26%, respectively (log-rank, p = 0.25). The results were similar in the PS-matched population. Hospital mortality was comparable between the two groups (18.9% vs. 17.4%, p = 0.074). The short-to-mid-term Kaplan-Meier survival analysis was similar for both groups, with 1-year, 3-year, and 5-year survival rates of 63.4%, 49.2%, and 24.7% versus 66.5%, 46%, and 25.1%, respectively (log-rank, p = 0.81). In the unmatched population, LVAD+CCP patients had longer intensive care unit (ICU) stays (p < 0.0001), longer mechanical ventilation time (p = 0.001), a higher rate of temporary right ventricular assist device (RVAD) support (p = 0.033), and a higher rate of renal replacement therapy (n = 35, 6.6% vs. n = 89, 4.0%, p = 0.014). In the PS-matched population, the LVAD+CCP patients had longer ICU stays (p = 0.019) and longer mechanical ventilation time (p = 0.002). CONCLUSIONS: The effect of additive valvular procedures (CCPs) does not seem to affect short-term survival, significantly, based on our registry data analysis. However, the decision to perform CCPs should be balanced with the projected type of surgery and preoperative characteristics. LVAD+CCP patients remain a delicate population and adverse device-related events should be strictly monitored and managed.

How Would the Authors Treat Their Own Temporary Left Ventricular Failure With Mechanical Circulatory Support?

In the last 20 years, mechanical circulatory supports (MCS) have overturned completely the outcomes and the clinical recovery of patients with isolated acute left ventricle failure (iALVF). This usually occurs more frequently than right-sided heart failure or biventricular dysfunction, and it mainly is caused by acute myocardial infarction. The primary role of MCS is to restore the tissue metabolism to preserve the vital organs' function but, on the other hand, they also have to relieve the workload stress on the heart. In this way, they allow not only the heart to recover from the acute event, but MCS also can stabilize the patient toward cardiac transplantation. The short-term MCS devices currently used in clinical practice are the intraaortic balloon pump, the Impella (Abiomed, Danvers, MA), and venoarterial extracorporeal membrane oxygenation (VA-ECMO), but the choice of the right and tailored device for each patient, as well as the timing to use it, is actually one of the most debated topics of MCS management.

Impact of prior sternotomy on survival and allograft function after heart transplantation: A single center matched analysis.

BACKGROUND: Orthotopic heart transplantation (OHT) remains the gold standard for the treatment of end-stage heart failure. The number of patients who have had at least one prior sternotomy while awaiting transplantation has increased over the years reaching 50% in the last ISHLT registry report. We analysed our institutional transplant activity focusing on prior-sternotomy setting to identify the real burden of this preoperative variable and its potential consequences. METHODS: Between 2000 and 2020, a total of 512 consecutive adult patients underwent OHT. We divided them into two groups according to the previous sternotomy variable: a prior sternotomy group (PS-group, n = 131, 25.6%) and a heart transplant as first sternotomy group (FS-group, n = 381, 74.4%). After propensity score matching, a total of 106 matched-pairs were identified for the final analysis. RESULTS: The overall 30-day mortality was similar in the two groups (7.5% vs. 5.7%, p = .58). The prior sternotomy was not an independent risk factor for 90-day mortality (odds ratio: 0.89, p = .81). In the matched sample, prior cardiac surgery was not predictive for any major postoperative complication: primary graft failure, AKI, bleeding, acute respiratory insufficiency, need for extra-corporeal life support (p > .05). The log-rank test revealed no significant difference between the two groups in the unmatched and matched pools (p = .93 and 0.69 respectively. At univariable analysis prior sternotomy was not associated with an increased risk of posttransplant mortality (hazard ratio: 0.87, p = .599). CONCLUSIONS: Despite it increases surgical complexity, the reoperation alone does not represent a proper risk factor and among different co-variates that may affect post-OHT outcomes.

Tuning the Magnetic Coupling of a Molecular Spin Interface via Electron Doping.

Mastering the magnetic response of molecular spin interfaces by tuning the occupancy of the molecular orbitals, which carry the spin magnetic moment, can be accomplished by electron doping. We propose a viable route to control the magnetization direction and magnitude of a molecular spin network, in a graphene-mediated architecture, achieved via alkali doping of manganese phthalocyanine (MnPc) molecules assembled on cobalt intercalated under a graphene membrane. The antiparallel magnetic alignment of the MnPc molecules with the underlying Co layer can be switched to a ferromagnetic state by electron doping. Multiplet calculations unveil an enhanced magnetic state of the Mn centers with a 3/2 to 5/2 spin transition induced by alkali doping, as confirmed by the steepening of the hysteresis loops, with higher saturation magnetization values. This new molecular spin configuration can be aligned by an external field, almost independently from the hard-magnet substrate effectively behaving as a free magnetic layer.

Towards free-standing graphane: atomic hydrogen and deuterium bonding to nano-porous graphene.

Graphane is formed by bonding hydrogen (and deuterium) atoms to carbon atoms in the graphene mesh, with modification from the pure planar sp2 bonding towards an sp3 configuration. Atomic hydrogen (H) and deuterium (D) bonding with C atoms in fully free-standing nano porous graphene (NPG) is achieved, by exploiting low-energy proton (or deuteron) non-destructive irradiation, with unprecedented minimal introduction of defects, as determined by Raman spectroscopy and by the C 1s core level lineshape analysis. Evidence of the H- (or D-) NPG bond formation is obtained by bringing to light the emergence of a H- (or D-) related sp3-distorted component in the C 1s core level, clear fingerprint of H-C (or D-C) covalent bonding. The H (or D) bonding with the C atoms of free-standing graphene reaches more than 1/4 (or 1/3) at% coverage. This non-destructive H-NPG (or D-NPG) chemisorption is very stable at high temperatures up to about 800 K, as monitored by Raman and x-ray photoelectron spectroscopy, with complete healing and restoring of clean graphene above 920 K. The excellent chemical and temperature stability of H- (and D-) NPG opens the way not only towards the formation of semiconducting graphane on large-scale samples, but also to stable graphene functionalisation enabling futuristic applications in advanced detectors for the ß-spectrum analysis.

Late acute aortic dissection following cardiac transplantation in lupus-affected donor aorta.

We report the case of a young woman who underwent cardiac transplantation from systemic lupus erythematosus affected donor and who developed a type A aortic dissection limited only to the graft aortic wall 9 years after.

Frozen Elephant Trunk in Aortic Arch Disease: Different Devices for Different Pathologies.

The frozen elephant trunk technique (FET) requires the use of a pre-assembled hybrid prosthesis consisting of a standard Dacron vascular portion to replace the aortic arch and a stent graft component, which is placed into the proximal descending thoracic aorta (DTA) anterogradely in the proximal descending thoracic aorta. In Europe, two hybrid prostheses are available: the E-evita Open Plus hybrid stent graft system provided by JOTEC (Hechingen, Germany) and the ThoraflexTM Hybrid (Vascutek, Inchinnan Scotland). Recommendations for use are extensive pathologies of the arch in case of acute and chronic aortic dissection, degenerative aneurysm and intramural hematoma. The FET approach allows the replacement of the whole arch in one stage with the option of direct treatment of the proximal descending thoracic aorta based on the stent component, creating a safe landing zone for further endovascular treatment more distally. The remarkable feature of this technique is the possibility to perform more proximally (from zone 3 to zone 0) the distal anastomosis in to the arch. This allows for an easier distal anastomosis, reduced hypothermic circulatory arrest time and decreased risk of paraplegia (<5%). Early results are promising and according to the most recent series the rate of developing post-operative renal insufficiency ranges from 3 to 10%, the risk of stroke from 3% to 8% and mortality from 8-15%. The aim of the article will be to provide some knowledge about the use and application of FET procedures in different aortic situations.

The GORE TAG conformable thoracic stent graft with the new ACTIVE CONTROL deployment system.

OBJECTIVE: The aim of this study was to describe single-center intraoperative details and early outcome of the new GORE TAG conformable stent graft with ACTIVE CONTROL (C-TAG ACTIVE CONTROL; W. L. Gore & Associates, Flagstaff, Ariz). METHODS: Between September 2017 and June 2018, a consecutive 30 patients underwent thoracic endovascular aortic repair with C-TAG ACTIVE CONTROL. This new system provides an intermediate deployment step at 50% and optional angulation control of the proximal part of the stent graft. Indications for thoracic endovascular aortic repair varied widely, including chronic postdissection and degenerative aneurysms, complicated acute dissections, and intramural hematomas, among others, in an elective (63.3%), urgent (13.3%), or emergent (23.3%) setting. The proximal landing zone (LZ) was LZ 2 in 23.3%, LZ 3 in 43.3%, and LZ 4 in 33.3%. Data were collected retrospectively and analyzed for technical and clinical success. RESULTS: In all patients, the stent graft was successfully introduced and deployed at the intended position, with complete exclusion of aortic disease and without intraoperative mortality (primary technical success, 100%). One emergent patient died at 2 days of ongoing septic shock (clinical success at 30 days, 96.6%). Median follow-up was 107 days (range, 33-271 days); late mortality was 3.4% (one patient died of stent graft infection at 40 days). Freedom from type I and type III endoleak at the early follow-up was 100%. No patients required other surgical or endovascular procedures for the primary treated aortic disease. CONCLUSIONS: Our reported initial experience in 30 patients with the C-TAG ACTIVE CONTROL showed excellent early results, with high deployment accuracy and conformability. The additional features of staged deployment and angulation control may be of great help in challenging aortic arch diseases, allowing precise positioning and preventing bird-beak effect.

Three-dimensional microporous graphene decorated with lithium.

Three-dimensional (3D) graphene-based architectures can combine the two-dimensional properties of graphene with the high surface-to-volume ratio required for a large variety of technological applications. We present a spectro-microscopy study of stable microporous 3D few-layer graphene structures with a very low density of defects/edges and of unsaturated bonds, as deduced by Raman and core level photoemission spectroscopy. These qualities make these interconnected graphene networks ideal candidates to accommodate lithium adatoms, with a high density of Li per unit volume and a Li uptake per C atom higher than the value observed for graphite, as confirmed by core level photoemission spectroscopy.

Chemical vapor deposition growth of boron-carbon-nitrogen layers from methylamine borane thermolysis products.

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

High quality epitaxial graphene by hydrogen-etching of 3C-SiC(111) thin-film on Si(111).

Etching with atomic hydrogen, as a preparation step before the high-temperature growth process of graphene onto a thin 3C-SiC film grown on Si(111), greatly improves the structural quality of topmost graphene layers. Pit formation and island coalescence, which are typical of graphene growth by SiC graphitization, are quenched and accompanied by widening of the graphene domain sizes to hundreds of nanometers, and by a significant reduction in surface roughness down to a single substrate bilayer. The surface reconstructions expected for graphene and the underlying layer are shown with atomic resolution by scanning tunnelling microscopy. Spectroscopic features typical of graphene are measured by core-level photoemission and Raman spectroscopy.

A long-range ordered array of copper tetrameric units embedded in an on-surface metal organic framework.

We report on the assembly of a highly ordered array of copper tetrameric clusters, coordinated into a metal-organic network. The ordered cluster array has been achieved by the deposition of tetrahydroxyquinone molecules on the Cu(111) surface at room temperature, and subsequent thermally activated dehydrogenation with the formation of tetraoxyquinone tetra-anions with a 4 × 4 periodicity. The supramolecular organic network acts as a spacer for the highly ordered two-dimensional network of copper tetramers at the very surface.

In-vacuum thermolysis of ethane 1,2-diamineborane for the synthesis of ternary borocarbonitrides.

High-temperature (1000 °C) thermolytic decomposition of ethane 1,2-diamineborane (BH3NH2CH2CH2NH2BH3) deposited onto a Cu foil has been performed in an ultra-high-vacuum environment. A combined thermolytic, structural (x-ray diffraction), microscopic (scanning electron microscopy) and spectroscopic (Raman, x-ray photoemission spectroscopy) analysis, has identified a ternary borocarbonitride (BCN) compound as a result of the process. The obtained BCN compound is nanocrystalline, surrounded by crystallites of ammonium hydroxide borate hydrate. The ternary compound presents a 0.2:0.6:0.2 B:C:N composition in the bulk and 0.11:0.76:0.13 stoichiometry at the very surface, richer in C-C networks with respect to the bulk. Furthermore, the resulting BCN compound does not show oxidation at the surface due to the in-vacuum thermolysis of the single precursor.

Outcome of emergency coronary artery bypass grafting.

OBJECTIVES: The aim of this study was to evaluate the immediate and late outcome of emergency coronary artery bypass grafting (CABG) in a multicenter setting. DESIGN: Multicenter, retrospective study. SETTING: Four university hospitals. PARTICIPANTS: 596 patients were included in this study. INTERVENTIONS: Included patients underwent isolated, emergency CABG. MEASUREMENTS AND MAIN RESULTS: Sixty patients (absolute rate: 10.1%, pooled rate: 8.7%) died during the in-hospital stay period. Increasing emergency CABG classes (p<0.0001), recent myocardial infarction (p=0.019), left ventricular ejection fraction≤30% (p=0.034), on-pump surgery (p=0.012), and participating centers (p<0.0001) were independent predictors of in-hospital mortality. Survival rates at 1, 3, and 5 years were 86.4%, 81.6%, and 76.1%, respectively. Extracorporeal membrane oxygenation was used in 6 patients and 3 of them (50.0%) survived the immediate postoperative period. Patient populations of participating centers differed significantly in most of baseline characteristics. The preoperative use of intra-aortic balloon pump (8% to 51%) and off-pump surgery (2.8% to 56.3%) varied significantly between institutions. In-hospital mortality (2.8%, 5.9%, 7.7% and 19.8%, p<0.0001), as well as midterm survival, significantly differed between institutions (at 3 years, 90.6%, 89.8%, 81.2%, and 67.2%, p<0.0001). CONCLUSIONS: The outcome after emergency CABG is satisfactory despite a significant operative risk. However, the results of emergency CABG significantly differed between the participating institutions, likely due to differences in the referral pathways and perioperative treatment strategies. Evaluation of these factors is crucial for implementation of treatment in centers with suboptimal results.

An advanced lithium-ion battery based on a graphene anode and a lithium iron phosphate cathode.

We report an advanced lithium-ion battery based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode in the round of few cycles, we demonstrate an optimal battery performance in terms of specific capacity, that is, 165 mAhg(-1), of an estimated energy density of about 190 Wh kg(-1) and a stable operation for over 80 charge-discharge cycles. The components of the battery are low cost and potentially scalable. To the best of our knowledge, complete, graphene-based, lithium ion batteries having performances comparable with those offered by the present technology are rarely reported; hence, we believe that the results disclosed in this work may open up new opportunities for exploiting graphene in the lithium-ion battery science and development.