| 1. |
- Backes, Claudia, et al.
(författare)
-
Production and processing of graphene and related materials
- 2020
-
Ingår i: 2D Materials. - : IOP Publishing. - 2053-1583. ; 7:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduce the results. Section I is devoted to 'bottom up' approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers 'top down' techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers' and modified Hummers' methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resource-consuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown. Section VIII discusses advances in GRM functionalization. A broad range of organic molecules can be anchored to the sp(2) basal plane by reductive functionalization. Negatively charged graphene can be prepared in liquid phase (e.g. via intercalation chemistry or electrochemically) and can react with electrophiles. This can be achieved both in dispersion or on substrate. The functional groups of GO can be further derivatized. Graphene can also be noncovalently functionalized, in particular with polycyclic aromatic hydrocarbons that assemble on the sp(2) carbon network by pi-pi stacking. In the liquid phase, this can enhance the colloidal stability of SLG/FLG. Approaches to achieve noncovalent on-substrate functionalization are also discussed, which can chemically dope graphene. Research efforts to derivatize CNMs are also summarized, as well as novel routes to selectively address defect sites. In dispersion, edges are the most dominant defects and can be covalently modified. This enhances colloidal stability without modifying the graphene basal plane. Basal plane point defects can also be modified, passivated and healed in ultra-high vacuum. The decoration of graphene with metal nanoparticles (NPs) has also received considerable attention, as it allows to exploit synergistic effects between NPs and graphene. Decoration can be either achieved chemically or in the gas phase. All LMs,
|
|
| 2. |
- Palmerini, Tullio, et al.
(författare)
-
Risk-Benefit of 1-Year DAPT After DES Implantation in Patients Stratified by Bleeding and Ischemic Risk.
- 2021
-
Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 1558-3597 .- 0735-1097. ; 78:20, s. 1968-1986
-
Tidskriftsartikel (refereegranskat)abstract
- Although a 1-year duration of dual antiplatelet therapy (DAPT) is used in many patients after drug-eluting stent (DES) implantation, the evidence supporting this duration is uncertain.The authors investigated the risk-benefit profile of 1-year vs≤6-month DAPT after DES using 2 novel scores to risk stratify bleeding and ischemic events.Ischemic and bleeding risk scores were generated from ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents), a multicenter, international, "all-comers" registry that enrolled 8,665 patients treated with DES. The risk-benefit profile of 1-year vs≤6-month DAPT was then investigated across risk strata from an individual patient data pooled dataset of 7 randomized trials that enrolled 15,083 patients treated with DES.In the derivation cohort, the ischemic score and the bleeding score had c-indexes of 0.76 and 0.66, respectively, and both were well calibrated. In the pooled dataset, no significant difference was apparent in any ischemic endpoint between 1-year and≤6-month DAPT, regardless of the risk strata. In the overall dataset, there was no significant difference in the risk of clinically relevant bleeding between 1-year and≤6-month DAPT; however, among 2,508 patients at increased risk of bleeding, 1-year compared with≤6-month DAPT was associated with greater bleeding (HR: 2.80; 95%CI: 1.12-7.13) without a reduced risk of ischemic events in any risk strata, including those with acute coronary syndromes. These results were consistent in a network meta-analysis.In the present large-scale study, compared with≤6-month DAPT, a 1-year duration of DAPT was not associated with reduced adverse ischemic events in any risk strata (including acute coronary syndromes) but was associated with greater bleeding in patients at increased risk of bleeding.
|
|
| 3. |
- Algaba, Juan-Carlos, et al.
(författare)
-
Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
- 2021
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
-
Forskningsöversikt (refereegranskat)abstract
- In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
|
|
| 4. |
- Bucchiarone, A., et al.
(författare)
-
POLYGLOT for Gamified Education : Mixing Modelling and Programming Exercises
- 2021
-
Ingår i: Companion Proceedings - 24th International Conference on Model-Driven Engineering Languages and Systems, MODELS-C 2021. - : IEEE. - 9781665424844 ; , s. 606-610
-
Konferensbidrag (refereegranskat)abstract
- Gamification refers to the employment of gaming mechanisms for non-gaming purposes. Its aim is promoting the engagement of target users in pursuing certain goals, e.g. completing education paths. In this paper we present POLYGLOT, a gamified notebook-like programming environment. The gamification extension was built to target programming languages education, and in this work we illustrate how the approach is adaptable to text-based modelling languages. In particular, we demonstrate the use of gamification tailored to SysML v2 modelling.Each exercise is defined as a sequence of steps framed into notebook cells. On each cell submission, the POLYGLOT extension for.NET interactive runs several analyzers to gain insights of the student code before invoking the gamification engine, which checks if the gathered data fits the teacher-defined expectations. Interestingly, since cell contents are language independent and exercise evaluations are delegated to the gamification engine, this solution enables the creation of heterogeneous narratives, that is gamification scenarios mixing languages in the proposed exercises.
|
|
| 5. |
- Kageyama, Shigetaka, et al.
(författare)
-
Geographic disparity in 10-year mortality after coronary artery revascularization in the SYNTAXES trial
- 2022
-
Ingår i: International Journal of Cardiology. - : Elsevier. - 0167-5273 .- 1874-1754. ; 368, s. 28-38
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: To investigate geographic disparity in long-term mortality following revascularization in patients with complex coronary artery disease (CAD).Methods and results: The SYNTAXES trial randomized 1800 patients with three-vessel and/or left main CAD to percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) and assessed their survival at 10 years. Patients were stratified according to the region of recruitment: North America (N-A, n = 245), Eastern Europe (E-E, n = 189), Northern Europe (N-E, n = 425), Southern Europe (S-E, n = 263), and Western Europe (W-E, n = 678), which also served as the reference group. Compared to W-E, patients were younger in E-E (62 vs 65 years, p < 0.001), and less frequently male in N-A (65.3% vs 79.6%, p < 0.001). Diabetes (16.0% vs 25.4%, p < 0.001) and peripheral vascular disease (6.8% vs 10.9%, p = 0.025) were less frequent in N-E than W-E. Ejection fraction was highest in W-E (62% vs 56%, p < 0.001). Compared to W-E, the mean anatomic SYNTAX score was higher in S-E (29 vs 31, p = 0.008) and lower in N-A (26, p < 0.001). Crude ten-year mortality was similar in N-A (31.6%), and W-E (30.7%), and significantly lower in E-E (22.5%, p = 0.041), N-E (21.9%, p = 0.003) and S-E (22.0%, p = 0.014). Compared to W-E, adjusted mortality in N-E (HR 0.85, p = 0.019) and S-E (HR 0.72, p = 0.043) remain significantly lower after adjustment for pre-and peri-procedural factors, but no significant interaction (Pinteraction = 0.728) between region and modality of revascularization was seen.Conclusion: In the era of globalization, knowledge, and understanding of geographic disparity are of paramount importance for the correct interpretation of global studies.
|
|
| 6. |
- Ponticelli, Francesco, et al.
(författare)
-
Safety and efficacy of coronary sinus narrowing in chronic refractory angina: Insights from the RESOURCE study.
- 2021
-
Ingår i: International journal of cardiology. - : Elsevier BV. - 1874-1754 .- 0167-5273. ; 337, s. 29-37
-
Tidskriftsartikel (refereegranskat)abstract
- Refractory angina (RA) is considered the end-stage of coronary artery disease, and often has no interventional treatment options. Coronary sinus Reducer (CSR) is a recent addition to the therapeutic arsenal, but its efficacy has only been evaluated on small populations. The RESOURCE registry provides further insights into this therapy.The RESOURCE is an observational, retrospective registry that includes 658 patients with RA from 20 centers in Europe, United Kingdom and Israel. Prespecified endpoints were the amelioration of anginal symptoms evaluated with the Canadian Cardiovascular Society (CCS) score, the rates of procedural success and complications, and MACEs as composite of all-cause mortality, acute coronary syndromes, and stroke.At a median follow-up of 502days (IQR 225-1091) after CSR implantation, 39.7% of patients improved by ≥2 CCS classes (primary endpoint), and 76% by ≥1 class. Procedural success was achieved in 96.7% of attempts, with 3% of procedures aborted mostly for unsuitable coronary sinus anatomy. Any complication occurred in 5.7% of procedures, but never required bailout surgery nor resulted in intra- or periprocedural death or myocardial infarction. One patient developed periprocedural stroke after inadvertent carotid artery puncture. At the last available follow-up, overall mortality and MACE were 10.4% and 14.6% respectively. At one, three and five years, mortality rate at Kaplan-Meier analysis was 4%, 13.7%, and 23.4% respectively.CSR implantation is safe and reduces angina in patients with refractory angina.
|
|
