| 1. |
- Augusto Silva, Iran, et al.
(författare)
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Formalin-free fixation and xylene-free tissue processing preserves cell-hydrogel interactions for histological evaluation of 3D calcium alginate tissue engineered constructs
- 2023
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Ingår i: Frontiers in Biomaterials Science. - 2813-3749. ; 2-2023:1155919
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Tidskriftsartikel (refereegranskat)abstract
- Histological evaluation of tissue-engineered products, including hydrogels for cellular encapsulation, is a critical and invaluable tool for assessing the product across multiple stages of its lifecycle from manufacture to implantation. However, many tissue-engineered products are comprised of polymers and hydrogels which are not optimized for use with conventional methods of tissue fixation and histological processing. Routine histology utilizes a combination of chemical fixatives, such as formaldehyde, and solvents such as xylene which have been optimized for use with native biological tissues due to their high protein and lipid content. Previous work has highlighted the challenges associated with processing hydrogels for routine histology due to their high water content and lack of diverse chemical moieties amenable for tissue fixation with traditional fixatives. Thus, hydrogel-based tissue engineering products are prone to histological artifacts during their validation which can lead to challenges in correctly interpreting results. In addition, chemicals used in conventional histological approaches are associated with significant health and environmental concerns due to their toxicity and there is thus an urgent need to identify suitable replacements. Here we use a multifactorial design of experiments approach to identify processing parameters capable of preserving cell-biomaterial interactions in a prototypical hydrogel system: ionically crosslinked calcium alginate. We identify a formalin free fixative which better retains cell-biomaterial interactions and calcium alginate hydrogel integrity as compared to the state-of-the-art formalin-based approaches. In addition, we demonstrate that this approach is compatible with a diversity of manufacturing techniques used to fabricate calcium alginate-based scaffolds for tissue engineering and cell therapy, including histological evaluation of cellular encapsulation in 3D tubes and thin tissue engineering scaffolds (∼50 μm). Furthermore, we show that formalin-free fixation can be used to retain cell-biomaterial interactions and hydrogel architecture in hybrid alginate-gelatin based scaffolds for use with histology and scanning electron microscopy. Taken together, these findings are a significant step forward towards improving histological evaluation of ionically crosslinked calcium alginate hydrogels and help make their validation less toxic, thus more environmentally friendly and sustainable.
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| 2. |
- Bagrov, Andrey A., et al.
(författare)
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Suppressing backscattering of helical edge modes with a spin bath
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 100:19
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Tidskriftsartikel (refereegranskat)abstract
- We address the question of stability of protected helical edge states at the boundary of two-dimensional topological insulators upon interactions with the external bath. We study how backscattering amplitude changes when different interaction channels between the system and the environment are present. Drawing an analogy with the concept of pointer states in theory of open quantum systems, we demonstrate that in a certain regime the interplay between the Coulomb and the spin-spin interactions can make the backscattering process strictly irrelevant, and the helical modes become robust states with a well-defined momentum. This opens a possibility to use the external spin bath as a stabilizer that alleviates destructive effects and restores the helicity protection.
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| 3. |
- Cappelluti, Emmanuele, et al.
(författare)
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Flat-band optical phonons in twisted bilayer graphene
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 108:12
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Tidskriftsartikel (refereegranskat)abstract
- Twisting bilayer sheets of graphene have been proven to be an efficient way to manipulate the electronic Dirac-like properties, resulting in flat bands at magic angles. Inspired by the electronic model, we develop a continuum model for the lattice dynamics of twisted bilayer graphene and we show that a remarkable band flattening applies to almost all the high-frequency in-plane lattice vibration modes, including the valley Dirac phonon, valley optical phonon, and zone-center optical phonon bands. Utilizing an approximate approach, we estimate small but finite magic angles at which a vanishing phonon bandwidth is expected. In contrast to the electronic case, the existence of a restoring potential prohibits the emergence of a magic angle in a more accurate modeling. The predicted phonon band flattening is highly tunable by the twist angle and this strong dependence is directly accessible by spectroscopic tools.
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| 4. |
- Ferrari, A. C., et al.
(författare)
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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:11, s. 4598-4810
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Tidskriftsartikel (refereegranskat)abstract
- We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
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| 5. |
- Geilhufe, Matthias, et al.
(författare)
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Hund nodal line semimetals : The case of a twisted magnetic phase in the double-exchange model
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 99:2
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Tidskriftsartikel (refereegranskat)abstract
- We propose a class of topological metals, which we dub Hund nodal line semimetals, arising from the strong Coulomb interaction encoded in the Hund's coupling between itinerant electrons and localized spins. We here consider a particular twisted spin configuration, which is realized in the double-exchange model which describes the manganite oxides. The resulting effective tetragonal lattice of electrons with hoppings tied to the local spin features an antiunitary nonsymmorphic symmetry that, in turn, together with another nonsymmorphic but unitary glide-mirror symmetry, protects crossings of a double pair of bands along a high-symmetry line on the Brillouin zone boundary. We also discuss the stability of Hund nodal line semimetals with respect to symmetry breaking arising from various perturbations of the twisted phase. Our results motivate further studies of other realizations of this state of matter, for instance, in different spin backgrounds, properties of its drumhead surface states, as well as its stability to disorder and interactions among the itinerant electrons.
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| 6. |
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| 7. |
- Roche, Stephan, et al.
(författare)
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Graphene spintronics : the European Flagship perspective
- 2015
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Ingår i: Current Opinion in Chemical Engineering. - : Institute of Physics Publishing (IOPP). - 2211-3398. ; 2:3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We review current challenges and perspectives in graphene spintronics, which is one of the most promising directions of innovation, given its room-temperature long-spin lifetimes and the ability of graphene to be easily interfaced with other classes of materials (ferromagnets, magnetic insulators, semiconductors, oxides, etc), allowing proximity effects to be harvested. The general context of spintronics is first discussed together with open issues and recent advances achieved by the Graphene Spintronics Work Package consortium within the Graphene Flagship project. Based on such progress, which establishes the state of the art, several novel opportunities for spin manipulation such as the generation of pure spin current (through spin Hall effect) and the control of magnetization through the spin torque phenomena appear on the horizon. Practical applications are within reach, but will require the demonstration of wafer-scale graphene device integration, and the realization of functional prototypes employed for determined applications such as magnetic sensors or nano-oscillators. This is a specially commissioned editorial from the Graphene Flagship Work Package on Spintronics. This editorial is part of the 2D Materials focus collection on 'Progress on the science and applications of two-dimensional materials,' published in association with the Graphene Flagship. It provides an overview of key recent advances of the spintronics work package as well as the mid-term objectives of the consortium.
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| 8. |
- Rostami, Habib, et al.
(författare)
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Piezoelectricity and valley chern number in inhomogeneous hexagonal 2D crystals
- 2018
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Ingår i: npj 2D Materials and Applications. - : Nature Publishing Group. - 2397-7132. ; 2, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of mechanical forces to electric signal is possible in non-centrosymmetric materials due to linear piezoelectricity. The extraordinary mechanical properties of two-dimensional materials and their high crystallinity make them exceptional platforms to study and exploit the piezoelectric effect. Here, the piezoelectric response of non-centrosymmetric hexagonal two-dimensional crystals is studied using the modern theory of polarization and k-p model Hamiltonians. An analytical expression for the piezoelectric constant is obtained in terms of topological quantities, such as the valley Chern number. The theory is applied to semiconducting transition metal dichalcogenides and hexagonal Boron Nitride. We find good agreement with available experimental measurements for MoS2. We further generalize the theory to study the polarization of samples subjected to inhomogeneous strain (e.g., nanobubbles). We obtain a simple expression in terms of the strain tensor, and show that charge densities greater than or similar to 10(11)cm(-2) can be induced by realistic inhomogeneous strains, epsilon approximate to 0.01-0.03.
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| 9. |
- Rostami, Habib, et al.
(författare)
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Strain-driven chiral phonons in two-dimensional hexagonal materials
- 2022
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 105:19
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Tidskriftsartikel (refereegranskat)abstract
- Hexagonal two-dimensional materials with broken inversion symmetry (as BN or transition metal dichalcogenides) are known to sustain chiral phonons with finite angular momentum, adding a further useful degree of freedom to the extraordinary entangled (electrical, optical, magnetic, and mechanical) properties of these compounds. However, because of lattice symmetry constraints, such chiral modes are constrained to the corners of the Brillouin zone, allowing little freedom for manipulating the chiral features. In this paper, we show how the application of uniaxial strain leads to the existence of unique chiral modes in the vicinity of the zone center. We also show that such strain-induced chiral modes, unlike the ones pinned at the K points, can be efficiently manipulated by modifying the strain itself, which determines the position of these modes in the Brillouin zone. The present paper results add a technique for the engineering of the quantum properties of two-dimensional lattices.
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| 10. |
- Wiesner, M., et al.
(författare)
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The electron-phonon interaction at deep Bi 2 Te3-semiconductor interfaces from Brillouin light scattering
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
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