Graphene setting the stage: tracking DNA hybridization with nanoscale resolution

In this study we use nanophotonic effects of graphene to study DNA hybridization: the z−4 nanoscale distance-dependence of the fluorescence lifetime for fluorophores located in the vicinity of graphene is for the first time used to track a DNA hybridization reaction with nanoscale resolution in real time. First, a nanostaircase with ≈2 nm steps from 0 to a total height of 48 nm is used as a nanoruler to confirm the distance dependence law. We find that the axial sensitivity is suited to determine the nanoscale surface roughness of these samples. The proof-of-concept DNA experiments in aqueous medium involve the hybridization of fluorescently labelled DNA beacons attached to CVD grown graphene with complementary (target) DNA added in solution. We track the conformational changes of the beacons statistically by determining the fluorescence lifetimes of the labelling dye and converting them into nanoscale distances from the graphene. In this way, we are able to monitor the vertical displacement of the label during DNA-beacon unfolding with an axial resolution reaching down to 1 nm. The measured distance increase during the DNA hybridization reaction of about 10 nm matches the length of the target DNA strand. Furthermore, the width of the fluorescence lifetime distributions could be used to estimate the molecular tilt angle of the hybridized ds-DNA configuration. The achieved nanoscale sensitivity opens innovation opportunities in material engineering, genetics, biochemistry and medicine.INL received support for this project from the CCDR-N via the project 'Nanotechnology based functional solutions' (Grant No. NORTE-01-0145-FEDER-000019) and from the Portuguese Foundation for Science and Technology (FCT) via the project 'ON4SupremeSens' PTDC/NAN-OPT/29417/2017. Edite Figueiras received a Marie Curie fellowship via the EU-EC COFUND program 'NanoTRAINforGrowth' (Grant No. 600375). U Minho research was partially supported by the FCT in the framework of the Strategic Funding UID/FIS/04650/2013

Spectral-temporal luminescence properties of Colloidal CdSe/ZnS Quantum Dots in relevant polymer matrices for integration in low turn-on voltage AC-driven LEDs

This work employs spectral and spectral-temporal Photoluminescence (PL) spectroscopy techniques to study the radiative mechanisms in colloidal CdSe/ZnS Quantum Dot (QD) thin films without and with 1% PMMA polymer matrix embedding (QDPMMA). The observed bimodal transient-spectral PL distributions reveal bandgap transitions and radiative recombinations after interdot electron transfer. The PMMA polymer embedding protects the QDs during the plasma-sputtering of inorganic layers electroluminescent (EL) devices, with minimal impact on the charge transfer properties. Further, a novel TiO2-based, all-electron bandgap, AC-driven QLED architecture is fabricated, yielding a surprisingly low turn-on voltage, with PL-identical and narrow-band EL emission. The symmetric TiO2 bilayer architecture is a promising test platform for alternative optical active materials.European Commission, Seventh Framework Programme (600375); European Commission, Horizon 2020 Framework Programme (828841); European Regional Development Fund, INTERREG V-A España-Portugal (POCTEP) 2014-2020 (0181_NANOEATERS_1_EP); CCDR-N (NORTE-01-0145-FEDER-000019); Fundação para a Ciência e a Tecnologia (UIDB/04650/2020)

Dwarf eelgrass (Zostera noltii) leaf fatty acid profile during a natural restoration process: Physiological and ecological implications

Seagrass beds are among the most relevant ecosystem engineers, providing essential ecosystem services for the surrounding coastal communities. Alongside, these ecosystems are among the most threaten in the world, and thus several restoration projects have been developed in the past years. Seagrasses are important sources of essential fatty acids (FA) for animals, which are unable to synthetize them. During the seagrass growth and photochemical maturation, there is a membrane remodelling, where some fatty acids are synthetized. When analysing the FA changes at different development stages, one of the first noticeable changes is the increase in C16:1t (trans-hexadecenoic acid), associated to an increase in the chloroplast membrane fluidity, essential for the efficient energy transduction processes to occur in the thylakoids. Also, interesting to observe are the high levels of omega-3 and -6 (30–43% and 18–31% of total fatty acid content, respectively) present in this seagrass, reinforcing the nutritional value of this species as source of essential fatty acids for the primary consumers. Additionally, it is possible to observe that in the more mature plants there is a high leaf concentration of C18:3. Recent reports suggest that C18:3 can act as a direct scavenger of reactive oxygen species (ROS), indicating a lower stress level, as suggested by the higher photochemical efficiency previously observed. Moreover, it is also interesting to observe that total long-chain polyunsaturated fatty acids (LC-PUFAs) content show a significant increase with the biomass development. These LC-PUFAs are not produced by higher plants and their production in animals occurs at low rates, suggesting they may have as origin the microalgae in the grass surface, adding another important ecosystem service to these prairies, as support for microalgae development and carriers of LC-PUFAs into the food web. This membrane remodelling appears to be on the basis of the photochemical maturation of these seagrasses observed in previous studies and can be used as potential and efficient tool to monitor the development stage of the prairies and its physiological status in future restoration processes. Moreover, it becomes evident that highly developed seagrass beds are crucial food source providers in terms of essential fatty acids to the estuarine heterotrophic life

Aquatic macrophytes assessment in the reservoir of hydroelectric power plant Luís Eduardo Magalhães (Tocantins State, Brazil)

As macrófitas aquáticas são importantes componentes dos recursos hídricos. Contudo, a presença excessiva dessas plantas pode diminuir o potencial de usos múltiplos de reservatórios. Nesse estudo visou-se monitorar, por um período de 4 anos (2004 a 2008) as macrófitas aquáticas do reservatório da Usina Hidrelétrica (UHE) Luís Eduardo Magalhães (UHE Lajeado), tendo em vista subsidiar o seu controle. Verificou-se que esse ambiente não apresenta atualmente macrófitas aquáticas em excesso (ca. 26 km2 ) e as espécies com maior cobertura são Salvinia auriculata e Oxycaryum cubense. As plantas encontram-se principalmente confinadas nos braços do reservatório ou em áreas protegidas da ação do vento e das correntezas. Devido à s características hidrodinâmicas (i.e. velocidade e direção da correnteza) e fetch elevado não se prevêem a propagação dessas plantas no corpo central do reservatório. As áreas ocupadas pelas plantas aquáticas têm-se mantido constantes (média: 3.7%), sugerindo que essa comunidade apresente tendência à estabilidade.The aquatic macrophytes are important components of the aquatic ecosystems. However, their excessive presence can decrease the potential of multiple uses of man-made reservoirs. The aim was to monitor the composition and cover of aquatic macrophytes in the Reservoir of Hydroelectric Power Plant Luís Eduardo Magalhães (HPP Lajeado) during four years. These parameter trends are indicators for aquatic weed control and environmental management decisions. The results showed that at sampling dates this reservoir did not show a critical high aquatic plant cover (ca. 26 km2 ) and the species with the largest distribution were Salvinia auriculata and Oxycaryum cubense. All the plants are mainly confined in the arms of the reservoir or within areas that are protected from the wind and currents. Due to their hydrodynamic characteristics and high fetch, their propagation is not foreseen in the central region of the reservoir. The areas occupied by the aquatic plants have remained constant (average: 3.7%), suggesting that this community tends to be stable.Comité de Medio Ambient

Circular and leakage resilient public-key encryption under subgroup indistinguishability (or: Quadratic residuosity strikes back)

30th Annual Cryptology Conference, Santa Barbara, CA, USA, August 15-19, 2010. ProceedingsThe main results of this work are new public-key encryption schemes that, under the quadratic residuosity (QR) assumption (or Paillier’s decisional composite residuosity (DCR) assumption), achieve key-dependent message security as well as high resilience to secret key leakage and high resilience to the presence of auxiliary input information. In particular, under what we call the subgroup indistinguishability assumption, of which the QR and DCR are special cases, we can construct a scheme that has: • Key-dependent message (circular) security. Achieves security even when encrypting affine functions of its own secret key (in fact, w.r.t. affine “key-cycles” of predefined length). Our scheme also meets the requirements for extending key-dependent message security to broader classes of functions beyond affine functions using previous techniques of Brakerski et al. or Barak et al. • Leakage resiliency. Remains secure even if any adversarial low-entropy (efficiently computable) function of the secret key is given to the adversary. A proper selection of parameters allows for a “leakage rate” of (1 − o(1)) of the length of the secret key. • Auxiliary-input security. Remains secure even if any sufficiently hard to invert (efficiently computable) function of the secret key is given to the adversary. Our scheme is the first to achieve key-dependent security and auxiliary-input security based on the DCR and QR assumptions. Previous schemes that achieved these properties relied either on the DDH or LWE assumptions. The proposed scheme is also the first to achieve leakage resiliency for leakage rate (1 − o(1)) of the secret key length, under the QR assumption. We note that leakage resilient schemes under the DCR and the QR assumptions, for the restricted case of composite modulus product of safe primes, were implied by the work of Naor and Segev, using hash proof systems. However, under the QR assumption, known constructions of hash proof systems only yield a leakage rate of o(1) of the secret key length.Microsoft Researc

Brain-inspired nanophotonic spike computing:challenges and prospects

Nanophotonic spiking neural networks (SNNs) based on neuron-like excitable subwavelength (submicrometre) devices are of key importance for realizing brain-inspired, power-efficient artificial intelligence (AI) systems with high degree of parallelism and energy efficiency. Despite significant advances in neuromorphic photonics, compact and efficient nanophotonic elements for spiking signal emission and detection, as required for spike-based computation, remain largely unexplored. In this invited perspective, we outline the main challenges, early achievements, and opportunities toward a key-enabling photonic neuro-architecture using III-V/Si integrated spiking nodes based on nanoscale resonant tunnelling diodes (nanoRTDs) with folded negative differential resistance. We utilize nanoRTDs as nonlinear artificial neurons capable of spiking at high-speeds. We discuss the prospects for monolithic integration of nanoRTDs with nanoscale light-emitting diodes and nanolaser diodes, and nanophotodetectors to realize neuron emitter and receiver spiking nodes, respectively. Such layout would have a small footprint, fast operation, and low power consumption, all key requirements for efficient nano-optoelectronic spiking operation. We discuss how silicon photonics interconnects, integrated photorefractive interconnects, and 3D waveguide polymeric interconnections can be used for interconnecting the emitter-receiver spiking photonic neural nodes. Finally, using numerical simulations of artificial neuron models, we present spike-based spatio-temporal learning methods for applications in relevant AI-based functional tasks, such as image pattern recognition, edge detection, and SNNs for inference and learning. Future developments in neuromorphic spiking photonic nanocircuits, as outlined here, will significantly boost the processing and transmission capabilities of next-generation nanophotonic spike-based neuromorphic architectures for energy-efficient AI applications. This perspective paper is a result of the European Union funded research project ChipAI in the frame of the Horizon 2020 Future and Emerging Technologies Open programme.</p

Subwavelength neuromorphic nanophotonic integrated circuits for spike-based computing : challenges and prospects

Event-activated biological-inspired subwavelength (sub-λ) optical neural networks are of paramount importance for energy-efficient and high-bandwidth artificial intelligence (AI) systems. Despite the significant advances to build active optical artificial neurons using for example phase-change materials, lasers, photodetectors, and modulators, miniaturized integrated sources and detectors suited for few-photon spike-based operation and of interest for neuromorphic optical computing are still lacking. In this invited paper we outline the main challenges, opportunities, and recent results towards the development of interconnected neuromorphic nanoscale light-emitting diodes (nanoLEDs) as key-enabling artificial spiking neuron circuits in photonic neural networks. This method of spike generation in neuromorphic nanoLEDs paves the way for sub-λ incoherent neural circuits for fast and efficient asynchronous brain-inspired computation