High Bandwidth GaN-Based Micro-LEDs for Multi-Gb/s Visible Light Communications

Gallium-nitride (GaN) based light-emitting diodes (LEDs) are highly-efficient sources for general purpose illumination. Furthermore, being semiconductor-based light sources, they are readily compatible with intelligent drive electronics. Visible light communications (VLC) is a technology which leverages these advantageous properties of GaN LEDs and can supplement existing wireless communications by offering a large, licence-free spectral bandwidth. Here we report on progress in the development of micro-scale GaN LEDs (micro-LEDs), optimised for VLC. These blue-emitting micro-LEDs are shown to have very high electrical-to-optical modulation bandwidths, exceeding 800~MHz. The data transmission capabilities of the micro-LEDs are illustrated by demonstrations using on-off-keying (OOK), pulse-amplitude modulation (PAM) and orthogonal frequency division multiplexing (OFDM) modulation schemes to transmit data over free space at rates of 1.7, 3.4 and 5 Gb/s, respectively

Biochar: pyrogenic carbon for agricultural use: a critical review.

O biocarvão (biomassa carbonizada para uso agrícola) tem sido usado como condicionador do solo em todo o mundo, e essa tecnologia é de especial interesse para o Brasil, uma vez que tanto a ?inspiração?, que veio das Terras Pretas de Índios da Amazônia, como o fato de o Brasil ser o maior produtor mundial de carvão vegetal, com a geração de importante quantidade de resíduos na forma de finos de carvão e diversas biomassas residuais, principalmente da agroindústria, como bagaço de cana, resíduos das indústrias de madeira, papel e celulose, biocombustíveis, lodo de esgoto etc. Na última década, diversos estudos com biocarvão têm sido realizados e atualmente uma vasta literatura e excelentes revisões estão disponíveis. Objetivou-se aqui não fazer uma revisão bibliográfica exaustiva, mas sim uma revisão crítica para apontar alguns destaques na pesquisa sobre biochar. Para isso, foram selecionados alguns temaschave considerados críticos e relevantes e fez-se um ?condensado? da literatura pertinente, mais para orientar as pesquisas e tendências do que um mero olhar para o passad

Riverine large woody debris introduced for natural flood management leads to rapid improvement in aquatic macroinvertebrate diversity

Natural flood management interventions, such as Large Wood Debris (LWD) or engineered log jams, are being increasingly deployed throughout the UK and elsewhere. In addition to alleviating flood risk, it is anticipated that they may influence the ecology of freshwater river systems, including macroinvertebrate populations. This study explores macroinvertebrate assemblages, water quality parameters, and sediment size distribution in a headwater stream following the addition of LWD as part of a natural flood management scheme. The study area consists of 6 sites within the intervention zone where LWD log jams were implemented, with comparative control sites upstream and downstream (3 sites each). Macroinvertebrate communities, sediment size distribution, and water chemistry were sampled 3 and 10 months following the addition of LWD. Our findings revealed increased macroinvertebrate abundance and taxa richness in the LWD intervention zone versus control, with an increased BMWP score reflecting the increased taxa richness. Average Score Per Taxon, and water chemistry showed no change, revealing invertebrate changes to be independent of water quality. NMDS and hierarchical clustering analysis on invertebrate data showed a clear separation of communities where LWD was present from those with no LWD, while SIMPER analysis showed that LWD addition led to the rapid establishment of taxa (Hydraenidae, Rhyacophilidae, Scirtidae, and Elmidae) that were otherwise absent. Ten months after LWD addition, improved biodiversity was also found in areas below the intervention zone, suggesting the positive impacts of LWD extend downstream. LWD also altered sediments, with sites immediately upstream of LWD log jams having a greater percentage of fine sediment than those immediately downstream. These results suggest that biological complexity and niche availability increased within the in-channel zone as a result of introduced LWD, thus revealing wider aquatic habitat improvement potential of LWD for natural flood management. The use of LWD as an intervention for flood management is recommended for its additional benefits for ecosystem health

Data link using wide field of view optical antenna based receiver

In this paper we describe the construction and fabrication of a VLC link that used novel micro-LEDs as a transmitter, and a planar fluorescent optical concentrator at the receiver. The link operates at 20Mbit/s and can transmit video streams between laptop computers

Label-free detection of DNA hybridization based on hydration-induced tension in nucleic acid films

The properties of water at the nanoscale are crucial in many areas of biology, but the confinement of water molecules in sub-nanometre channels in biological systems has received relatively little attention. Advances in nanotechnology make it possible to explore the role played by water molecules in living systems, potentially leading to the development of ultrasensitive biosensors. Here we show that the adsorption of water by a self-assembled monolayer of single-stranded DNA on a silicon microcantilever can be detected by measuring how the tension in the monolayer changes as a result of hydration. Our approach relies on the microcantilever bending by an amount that depends on the tension in the monolayer. In particular, we find that the tension changes dramatically when the monolayer interacts with either complementary or single mismatched single-stranded DNA targets. Our results suggest that the tension is mainly governed by hydration forces in the channels between the DNA molecules and could lead to the development of a label-free DNA biosensor that can detect single mutations. The technique provides sensitivity in the femtomolar range that is at least two orders of magnitude better than that obtained previously with label-free nanomechanical biosensors and with label-dependent microarrays.D.R. acknowledges the fellowship funded by the Autonomic Community of Madrid (CAM). J.T, M.C, J.M and D.R acknowledge financial support by Spanish Ministry of Science (MEC) under grant No. TEC2006-10316 and CAM under grant No. 200550M056. C.B. acknowledges funding provided by MEC under grant No. BIO2007-67523. Work at Centro de Astrobiología was supported by European Union (EU), Instituto Nacional de Técnica Aeroespacial (INTA), MEC and CAM. All the authors acknowledge A. Cebollada, J.M. García-Martín, J. García, J.L. Costa-Kramer, M. Arroyo-Hernández and J.V. Anguita for their assistance in the gold deposition on the cantilevers.Peer reviewe

Direct detection of a BRAF mutation in total RNA from melanoma cells using cantilever arrays.

Malignant melanoma, the deadliest form of skin cancer, is characterized by a predominant mutation in the BRAF gene. Drugs that target tumours carrying this mutation have recently entered the clinic. Accordingly, patients are routinely screened for mutations in this gene to determine whether they can benefit from this type of treatment. The current gold standard for mutation screening uses real-time polymerase chain reaction and sequencing methods. Here we show that an assay based on microcantilever arrays can detect the mutation nanomechanically without amplification in total RNA samples isolated from melanoma cells. The assay is based on a BRAF-specific oligonucleotide probe. We detected mutant BRAF at a concentration of 500 pM in a 50-fold excess of the wild-type sequence. The method was able to distinguish melanoma cells carrying the mutation from wild-type cells using as little as 20 ng µl(-1) of RNA material, without prior PCR amplification and use of labels