| 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. |
- Kattge, Jens, et al.
(författare)
-
TRY plant trait database - enhanced coverage and open access
- 2020
-
Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
-
Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
|
|
| 3. |
- Billing, Erik, PhD, 1981-, et al.
(författare)
-
The DREAM Dataset : Supporting a data-driven study of autism spectrum disorder and robot enhanced therapy
- 2020
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 15:8
-
Tidskriftsartikel (refereegranskat)abstract
- We present a dataset of behavioral data recorded from 61 children diagnosed with Autism Spectrum Disorder (ASD). The data was collected during a large-scale evaluation of Robot Enhanced Therapy (RET). The dataset covers over 3000 therapy sessions and more than 300 hours of therapy. Half of the children interacted with the social robot NAO supervised by a therapist. The other half, constituting a control group, interacted directly with a therapist. Both groups followed the Applied Behavior Analysis (ABA) protocol. Each session was recorded with three RGB cameras and two RGBD (Kinect) cameras, providing detailed information of children’s behavior during therapy. This public release of the dataset comprises body motion, head position and orientation, and eye gaze variables, all specified as 3D data in a joint frame of reference. In addition, metadata including participant age, gender, and autism diagnosis (ADOS) variables are included. We release this data with the hope of supporting further data-driven studies towards improved therapy methods as well as a better understanding of ASD in general.
|
|
| 4. |
- Cadenas-Sanchez, Cristina, et al.
(författare)
-
Differences in Brain Volume between Metabolically Healthy and Unhealthy Overweight and Obese Children : The Role of Fitness
- 2020
-
Ingår i: Journal of Clinical Medicine. - : MDPI. - 2077-0383. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine whether metabolically healthy overweight/obese children have greater global and regional gray matter volumes than their metabolically unhealthy peers. We further examined the association between gray matter volume and academic achievement, along with the role of cardiorespiratory fitness in these associations. A total of 97 overweight/obese children (10.0 +/- 1.2 years) participated. We classified children as metabolically healthy/unhealthy based on metabolic syndrome cut-offs. Global and regional brain volumes were assessed by magnetic resonance imaging. Academic achievement was assessed using the Woodcock-Munoz standardized test. Cardiorespiratory fitness was assessed by the 20 m shuttle run test. Metabolically healthy overweight/obese (MHO) children had greater regional gray matter volume compared to those who were metabolically unhealthy (MUO) (all p <= 0.001). A similar trend was observed for global gray matter volume (p = 0.06). Global gray matter volume was positively related to academic achievement (beta = 0.237, p = 0.036). However, all the associations were attenuated or disappeared after adjusting for cardiorespiratory fitness (p > 0.05). The findings of the present study support that metabolically healthy overweight/obese children have greater gray matter volume compared to those that are metabolically unhealthy, which is in turn related to better academic achievement. However, cardiorespiratory fitness seems to explain, at least partially, these findings.
|
|
| 5. |
- Grande, Virginia, 1987-, et al.
(författare)
-
Everybody Rock Your Equity : Experiences of Organizing a Women in Computing Event with Role Models for Diversity and Inclusion
- 2020
-
Ingår i: Digital Transformation for a Sustainable Society in the 21st Century. - Cham : Springer Nature. - 9783030396343 - 9783030396336 ; , s. 5-16
-
Konferensbidrag (refereegranskat)abstract
- This paper describes the experiences of organizing an event to celebrate women in computing in Spain. We present how the idea of the event was conceived and what the aims with its organization are from its conception, including providing a network and role models for the participants based on role model theory. We then explain how these aims have been implemented for each of the four editions of the event, and we include data for them. Finally, we compile recommendations for readers interested in launching an event of these characteristics and we reflect on the work to be done in the future.
|
|
| 6. |
|
|
| 7. |
- Niss, Kristoffer, et al.
(författare)
-
Complete Topological Mapping of a Cellular Protein Interactome Reveals Bow-Tie Motifs as Ubiquitous Connectors of Protein Complexes
- 2020
-
Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 31:11
-
Tidskriftsartikel (refereegranskat)abstract
- The network topology of a protein interactome is shaped by the function of each protein, making it a resource of functional knowledge in tissues and in single cells. Today, this resource is underused, as complete network topology characterization has proved difficult for large protein interactomes. We apply a matrix visualization and decoding approach to a physical protein interactome of a dendritic cell, thereby characterizing its topology with no prior assumptions of structure. We discover 294 proteins, each forming topological motifs called “bow-ties” that tie together the majority of observed protein complexes. The central proteins of these bow-ties have unique network properties, display multifunctional capabilities, are enriched for essential proteins, and are widely expressed in other cells and tissues. Collectively, the bow-tie motifs are a pervasive and previously unnoted topological trend in cellular interactomes. As such, these results provide fundamental knowledge on how intracellular protein connectivity is organized and operates. Niss et al. show that topological motifs called bow-ties create a scaffold within the cellular protein interactome that connects a majority of protein complexes. The central proteins of these motifs are found to be associated with multifunctionality and cellular essentiality, display unique network properties, and are expressed widely across cells and tissues.
|
|
| 8. |
- Palau-Rodriguez, Magali, et al.
(författare)
-
Effects of a long-term lifestyle intervention on metabolically healthy women with obesity: Metabolite profiles according to weight loss response
- 2020
-
Ingår i: Clinical Nutrition. - : Elsevier BV. - 1532-1983 .- 0261-5614. ; 39:1, s. 215-224
-
Tidskriftsartikel (refereegranskat)abstract
- Background & aims: The benefits of weight loss in subjects with metabolically healthy obesity (MHO) are still a matter of controversy. We aimed to identify metabolic fingerprints and their associated pathways that discriminate women with MHO with high or low weight loss response after a lifestyle intervention, based on a hypocaloric Mediterranean diet (MedDiet) and physical activity. Methods: A UPLC-Q-Exactive-MS/MS metabolomics workflow was applied to plasma samples from 27 women with MHO before and after 12 months of a hypocaloric weight loss intervention with a MedDiet and increased physical activity. The subjects were stratified into two age-matched groups according to weight loss: <10% (low weight loss group, LWL) and >10% (high weight loss group, HWL). Random forest analysis was performed to identify metabolites discriminating between the LWL and the HWL as well as within-status effects. Modulated pathways and associations between metabolites and anthropometric and biochemical variables were also investigated. Results: Thirteen metabolites discriminated between the LWL and the HWL, including 1,5-anhydroglucitol, carotenediol, 3-(4-hydroxyphenyl)lactic acid, N-acetylaspartate and several lipid species (steroids, a plasmalogen, sphingomyelins, a bile acid and long-chain acylcarnitines). 1,5-anhydroglucitol, 3-(4-hydroxyphenyl)lactic acid and sphingomyelins were positively associated with weight variables whereas N-acetylaspartate and the plasmalogen correlated negatively with them. Changes in very long-chain acylcarnitines and hydroxyphenyllactic levels were observed in the HWL and positively correlated with fasting glucose, and changes in levels of the plasmalogen negatively correlated with insulin resistance. Additionally, the cholesterol profile was positively associated with changes in acid hydroxyphenyllactic, sphingolipids and 1,5-AG. Conclusions: Higher weight loss after a hypocaloric MedDiet and increased physical activity for 12 months is associated with changes in the plasma metabolome in women with MHO. These findings are associated with changes in biochemical variables and may suggest an improvement of the cardiometabolic risk profile in those patients that lose greater weight. Further studies are needed to investigate whether the response of those subjects with MHO to this intervention differs from those with unhealthy obesity.
|
|
| 9. |
- Yaghootkar, Hanieh, et al.
(författare)
-
Genetic Studies of Leptin Concentrations Implicate Leptin in the Regulation of Early Adiposity
- 2020
-
Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 69:12, s. 2806-2818
-
Tidskriftsartikel (refereegranskat)abstract
- Leptin influences food intake by informing the brain about the status of body fat stores. Rare LEP mutations associated with congenital leptin deficiency cause severe early-onset obesity that can be mitigated by administering leptin. However, the role of genetic regulation of leptin in polygenic obesity remains poorly understood. We performed an exome-based analysis in up to 57,232 individuals of diverse ancestries to identify genetic variants that influence adiposity-adjusted leptin concentrations. We identify five novel variants, including four missense variants, in LEP, ZNF800, KLHL31, and ACTL9, and one intergenic variant near KLF14. The missense variant Val94Met (rs17151919) in LEP was common in individuals of African ancestry only, and its association with lower leptin concentrations was specific to this ancestry (P = 2 × 10-16, n = 3,901). Using in vitro analyses, we show that the Met94 allele decreases leptin secretion. We also show that the Met94 allele is associated with higher BMI in young African-ancestry children but not in adults, suggesting that leptin regulates early adiposity.
|
|
| 10. |
- Youssef, Lina, et al.
(författare)
-
Fetal cardiac remodeling and dysfunction is associated with both preeclampsia and fetal growth restriction
- 2020
-
Ingår i: American Journal of Obstetrics and Gynecology. - : Elsevier BV. - 0002-9378. ; 222:1, s. 1-79
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Preeclampsia and fetal growth restriction share some pathophysiologic features and are both associated with placental insufficiency. Fetal cardiac remodeling has been described extensively in fetal growth restriction, whereas little is known about preeclampsia with a normally grown fetus. Objective: To describe fetal cardiac structure and function in pregnancies complicated by preeclampsia and/or fetal growth restriction as compared with uncomplicated pregnancies. Study design: This was a prospective, observational study including pregnancies complicated by normotensive fetal growth restriction (n=36), preeclampsia with a normally grown fetus (n=35), preeclampsia with fetal growth restriction (preeclampsia with a normally grown fetus–fetal growth restriction, n=42), and 111 uncomplicated pregnancies matched by gestational age at ultrasound. Fetal echocardiography was performed at diagnosis for cases and recruitment for uncomplicated pregnancies. Cord blood concentrations of B-type natriuretic peptide and troponin I were measured at delivery. Univariate and multiple regression analysis were conducted. Results: Pregnancies complicated by preeclampsia and/or fetal growth restriction showed similar patterns of fetal cardiac remodeling with larger hearts (cardiothoracic ratio, median [interquartile range]: uncomplicated pregnancies 0.27 [0.23–0.29], fetal growth restriction 0.31 [0.26–0.34], preeclampsia with a normally grown fetus 0.31 [0.29–0.33), and preeclampsia with fetal growth restriction 0.28 [0.26–0.33]; P<.001) and more spherical right ventricles (right ventricular sphericity index: uncomplicated pregnancies 1.42 [1.25–1.72], fetal growth restriction 1.29 [1.22–1.72], preeclampsia with a normally grown fetus 1.30 [1.33–1.51], and preeclampsia with fetal growth restriction 1.35 [1.27–1.46]; P=.04) and hypertrophic ventricles (relative wall thickness: uncomplicated pregnancies 0.55 [0.48–0.61], fetal growth restriction 0.67 [0.58–0.8], preeclampsia with a normally grown fetus 0.68 [0.61–0.76], and preeclampsia with fetal growth restriction 0.66 [0.58–0.77]; P<.001). Signs of myocardial dysfunction also were observed, with increased myocardial performance index (uncomplicated pregnancies 0.78 z scores [0.32–1.41], fetal growth restriction 1.48 [0.97–2.08], preeclampsia with a normally grown fetus 1.15 [0.75–2.17], and preeclampsia with fetal growth restriction 0.45 [0.54–1.94]; P<.001) and greater cord blood B-type natriuretic peptide (uncomplicated pregnancies 14.2 [8.4–30.9] pg/mL, fetal growth restriction 20.8 [13.1–33.5] pg/mL, preeclampsia with a normally grown fetus 31.8 [16.4–45.8] pg/mL and preeclampsia with fetal growth restriction 37.9 [15.7–105.4] pg/mL; P<.001) and troponin I as compared with uncomplicated pregnancies. Conclusion: Fetuses of preeclamptic mothers, independently of their growth patterns, presented cardiovascular remodeling and dysfunction in a similar fashion to what has been previously described for fetal growth restriction. Future research is warranted to better elucidate the mechanism(s) underlying fetal cardiac adaptation in these conditions.
|
|
