37 research outputs found
Cells on hierarchically-structured platforms hosting functionalized nanoparticles
No full textIn this work, we report on a novel approach to develop hierarchically-structured cell culture platforms incorporating functionalized gold nanoparticles (AuNPs). In particular, the hierarchical substrates comprise primary pseudo-periodic arrays of silicon microcones combined with a secondary nanoscale pattern of homogenously deposited AuNPs terminated with bio-functional moieties. AuNPs with various functionalities (i.e. oligopeptides, small molecules and oligomers) were successfully attached onto the microstructures. Experiments with PC12 cells on the hierarchical substrates incorporating AuNPs carrying the RGD peptide showed an impressive growth and NGF-induced differentiation of the PC12 cells, compared to that on the NPs-free, bare, micropatterned substrates. The exploitation of the developed methodology for the binding of AuNPs as carriers of specific bio-functional moieties onto micropatterned culture substrates for cell biology studies is envisaged
Biomimetic surface structuring using cylindrical vector femtosecond laser beams
No full textAbstractWe report on a new, single-step and scalable method to fabricate highly ordered, multi-directional and complex surface structures that mimic the unique morphological features of certain species found in nature. Biomimetic surface structuring was realized by exploiting the unique and versatile angular profile and the electric field symmetry of cylindrical vector (CV) femtosecond (fs) laser beams. It is shown that, highly controllable, periodic structures exhibiting sizes at nano-, micro- and dual- micro/nano scales can be directly written on Ni upon line and large area scanning with radial and azimuthal polarization beams. Depending on the irradiation conditions, new complex multi-directional nanostructures, inspired by the Shark’s skin morphology, as well as superhydrophobic dual-scale structures mimicking the Lotus’ leaf water repellent properties can be attained. It is concluded that the versatility and features variations of structures formed is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV fields, the present technique can be further extended to fabricate even more complex and unconventional structures. We believe that our approach provides a new concept in laser materials processing, which can be further exploited for expanding the breadth and novelty of applications.</jats:p
Grid Operation Assessment under a Specific EV Chargers Deployment Plan in the City of Heraklion
No full textThe development of electric vehicles (EVs) as part of the electrification of the transportation sector plays a significant role in energy transition to a low-carbon and highly renewable society. The use of EVs has been promoted through the development of inclusive strategies for electromobility in the recent years. Apart from actions directed and funded by the European Union, national strategies have also been employed to support electromobility. Such a strategic plan has already been enacted by the Hellenic Ministry of Environment and Energy, funding municipalities to prepare siting and sizing plans for electric vehicle chargers. In this paper, the final study of this strategic plan for the municipality of Heraklion in Crete is used as a case study to investigate the effect of EV chargers on the operation of the Cretan power system. Their selected siting points are evaluated by performing a power flow analysis at the level of 150 kV. Thus, they are aggregated in each 20 kV/150 kV distribution substation of the electrical grid with the aim of investigating their effect on substation loading and transmission line losses. Generally, extensive fast charging should be avoided to minimize the risk of sudden stress of the existing cities’ grids and control strategies should be implemented to mitigate the need for upscale substation equipment or even postpone reinforcements
Flexible Organic Photovoltaic Cells with In Situ Nonthermal Photoreduction of Spin‐Coated Graphene Oxide Electrodes
No full textFine-grained parameterized complexity analysis of graph coloring problems
No full textThe q-Coloring problem asks whether the vertices of a graph can be properly colored with q colors. Lokshtanov et al. [SODA 2011] showed that q-Coloring on graphs with a feedback vertex set of size k cannot be solved in time O ∗ ((q−ε) k ) O∗((q−ε)k) , for any ε>0 ε>0 , unless the Strong Exponential-Time Hypothesis (SETH SETH ) fails. In this paper we perform a fine-grained analysis of the complexity of q-Coloring with respect to a hierarchy of parameters. We show that unless ETH ETH fails, there is no universal constant θ θ such that q-Coloring parameterized by vertex cover can be solved in time O ∗ (θ k ) O∗(θk) for all fixed q. We prove that there are O ∗ ((q−ε) k ) O∗((q−ε)k) time algorithms where k is the vertex deletion distance to several graph classes F F for which q-Coloring is known to be solvable in polynomial time, including all graph classes whose (q+1) (q+1) -colorable members have bounded treedepth. In contrast, we prove that if F F is the class of paths – some of the simplest graphs of unbounded treedepth – then no such algorithm can exist unless SETH SETH fails. This research was partially funded by the Networks programme via the Dutch Ministry of Education, Culture and Science through the Netherlands Organisation for Scientific Research. The research was done while the first author was at CWI, Amsterdam. The second author was supported by NWO Veni grant “Frontiers in Parameterized Preprocessing”
