130,590 research outputs found
Controlling non-radiative energy transfer in organic binary blends: a route towards colour tunability and white emission from single-active-layer light-emitting devices
No full textWe show how colour tunability (including white) can be achieved by controlling non-radiative intermolecular energy transfer from the donor to the acceptor in binary blends of oligomeric compounds. Blends of different concentrations of a novel functionalized thiophene-based oligomer and a low-molar-mass diamine derivative (N, N'-diphenyl-N, N'-bis(3-methylphenyl)-1,1'-biphenyl-4.4'diamine) are used to tune both the photoluminescence and the electroluminescence (EL) from red to blue, including balanced white, according to the standards of the Commission Internationale de l'Eclairage. The single-active-layer light-emitting devices, realized by spin-coating, exhibit good EL performance. In particular, the white-emitting device shows an EL efficiency of 5 x 10(-1) cd A(-1) and a luminance of more than 180 cd m(-2)
The Heterogeneity of Renal Stem Cells and Their Interaction with Bio- and Nano-materials
No full textFor a long time, the kidney has been considered incapable of regeneration. Instead, in recent years, studies have supported the existence of heterogeneity of renal stem/progenitor cells with the ability to regenerate both glomerular and tubular epithelial cells. Indeed, several studies evidence that renal progenitor cells, releasing chemokines, growth factors, microvesicles, and transcription factors through paracrine mechanisms, can induce tissue regeneration and block pathological processes of the kidney. In this chapter the potentiality of the kidney regenerative processes is considered and reviewed, and the main classes of stem/progenitor cells that might contribute to the renal tissue renewal is analyzed. Moreover, we evaluate the role of biomaterials in the regulation of cellular functions, specifically addressing renal stem/progenitor cells. Materials can be synthesized and tailored in order to recreate a finely structured microenvironment (by nanostructures, nanofibers, bioactive compounds, etc.) with which the cells can interact actively. For instance, by patterning substrates in regions that alternately promote or prevent protein adsorption, cell adhesion and spreading processes can be controlled in space. We illustrate the potentiality of nanotechnologies and engineered biomaterials in affecting and enhancing the behavior of renal stem/progenitor cells. Although there are still many challenges for the translation of novel therapeutics, advances in biomaterials and nanomedicine have the potential to drastically change the clinical and therapeutic landscape, even in combination with stem cell biology
Maneuvering the Migration and Differentiation of Stem Cells with Electrospun Nanofibers
No full textElectrospun nanofibers have been extensively explored as a class of scaffolding materials for tissue regeneration, because of their unique capability to mimic some features and functions of the extracellular matrix, including the fibrous morphology and mechanical properties, and to a certain extent the chemical/biological cues. This work reviews recent progress in applying electrospun nanofibers to direct the migration of stem cells and control their differentiation into specific phenotypes. First, the physicochemical properties that make electrospun nanofibers well-suited as a supporting material to expand stem cells by controlling their migration and differentiation are introduced. Then various systems are analyzed in conjunction with mesenchymal, neuronal, and embryonic stem cells, as well as induced pluripotent stem cells. Finally, some perspectives on the challenges and future opportunities in combining electrospun nanofibers with stem cells are offered to address clinical issues
Realization of submicrometer structures by a confocal system on azo-polymer films containing photoluminescent chromophores
No full textThe mass migration phenomenon occurring on the free surface of azobenzene-containing polymers illuminated by light of appropriate wavelength is employed to pattern polymeric films constituted by an azopolymer doped with photoluminescent chromophore. Diff
In silico broadband mechanical spectroscopy of amorphous tantala
No full textAdopting an agnostic approach, the quality factor Q of tantala glass is drawn via in silico mechanical spectroscopy in wide ranges of temperature (10–300 K) and frequency (500 MHz f 1 THz). At the highest frequencies, Q ∝ f −3, consistent with Rayleigh sound scattering. For frequencies lower than terahertz, losses exhibit a weak power-law frequency dependence Q ∝ f −α with α ∼ 0.1 to 0.2, depending on glass preparation and temperature. Arguing the validity of the power law down to 1 kHz, we show striking agreement with the losses measured in annealed amorphous films in the whole temperature range, revealing similitude between disordered structures created by different routes (quench cooling and deposition). Our results do not support the scenario of the mechanical loss due to activated relaxation of independent two-level system
Non-local cooperative atomic motions that govern dissipation in amorphous tantala unveiled by dynamical mechanical spectroscopy
No full textThe mechanisms governing mechanical dissipation in amorphous tantala are studied at microscopic scale via Molecular Dynamics simulations, namely by mechanical spectroscopy in a wide range of temperature and frequency. We find that dissipation is associated with irreversible atomic rearrangements with a sharp cooperative character, involving tens to hundreds of atoms arranged in spatially extended clusters of polyhedra. Remarkably, at low temperature we observe an excess of plastically rearranging oxygen atoms which correlates with the experimental peak in the macroscopic mechanical losses. A detailed structural analysis reveals preferential connections of the irreversibly rearranging polyhedra, corresponding to edge and face sharing. These results might lead to microscopically informed design rules for reducing mechanical losses in relevant materials for structural, optical, and sensing applications
Controlling spontaneous surface structuring of azobenzene-containing polymers for large-scale nano-lithography of functional substrates
No full textEvidence of negative thermal expansion in supercooled tantala
No full textA density anomaly, i.e. a temperature region with negative thermal expansion (NTE) bounded by a density maximum and a density minimum at lower temperatures, is revealed and characterised in tantala for the first time by Molecular Dynamics simulations. The NTE region is evidenced in the metastable supercooled liquid and rather close to the glass transition. Since NTE is suppressed by poor structural equilibration, highlighting these phenomena is highly challenging due to the need for fulfilling competing constraints of slow cooling and avoidance of the crystallization. We find that the density anomaly is signalled by a decrease of the partial coordination numbers nTa,Ta and nO,O when lowering the temperature. The NTE magnitude is comparable to the ones of both stable water and solid-state materials with giant NTE
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