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Cellulose nanocrystals (CNCs) derived from native cellulose can self-assemble into liquid crystals (LCs) and preserve the LC alignment in solid films that are attractive for the preparation of optical materials and devices from bottom-up manufacturing. Birefringent aligned CNC films provide the desired phase retardation for a narrow band of wavelengths due to the intrinsic wavelength-dependent birefringence of CNCs. Here, we produce a 1/4 λ achromatic CNC-based waveplate consisting of three layers of birefringent CNC films with phase retardations and slow axis directions, which are calculated by Jones Matrix, with optimized achromatic properties. Three uniform CNC films are prepared by aligning nematic CNC LCs doped with polyethylene glycol on patterned polydimethylsiloxane substrates. The fabricated achromatic waveplate is characterized by measuring the transmission spectra, and its maximum deviation of phase retardation is around 0.06 for the wavelength range of 460–660 nm. The achromatic performance is improved by one order of magnitude compared with the single birefringent CNC films. Our CNC-based achromatic waveplate has good optical homogeneity, flexibility and can be tailored into arbitrary shape.

Understanding the behavior of fluids with inhomogeneous structural properties is critical for many industrial and biological materials. Sulfuric acid hydrolysis of cotton with ultrasonic treatment and low-speed centrifugation during purification yields “spiky” discotic cellulose particles. Amorphous cellulose remained in solution and forms discotic units which may be nucleated by crystalline rods. Scanning electron microscope and transmission electron microscope images confirm the discotic nature of the cellulose. High speed centrifugation could recover rod-like cellulose nanocrystals from the discotic cellulose nanoparticle solution. 3.6 wt% discotic cellulose nanoparticles formed the typical nematic phase and the liquid crystal texture became more structured with increasing concentration. Our results showed that spontaneous structuring of amorphous cellulose can lead to phase behavior that cannot be achieved using just rod-like cellulose nanocrystals. Mixtures containing amorphous and crystalline cellulose can form discotic cellulose nanoparticles. These solutions can form nematic phase (A), a structured columnar-like phase (B), and a glassy phase (C). Scanning electron microscope characterization (D, E) confirms a discotic structure with some spikes and network formation

Optical nanoantennas can convert propagating light to local fields. The local-field responses can be engineered to exhibit nontrivial features in spatial, spectral and temporal domains, where local-field interferences play a key role. Here, we design nearly fully controllable local-field interferences in the nanogap of a nanoantenna, and experimentally demonstrate that in the nanogap, the spectral dispersion of the local-field response can exhibit tuneable Fano lineshapes with nearly vanishing Fano dips. A single quantum dot is precisely positioned in the nanogap to probe the spectral dispersions of the local-field responses. By controlling the excitation polarization, the asymmetry parameter q of the probed Fano lineshapes can be tuned from negative to positive values, and correspondingly, the Fano dips can be tuned across a broad spectral range. Notably, at the Fano dips, the local-field intensity is strongly suppressed by up to ~50-fold, implying that the hot spot in the nanogap can be turned into a cold spot. The results may inspire diverse designs of local-field responses with novel spatial distributions, spectral dispersions and temporal dynamics, and expand the available toolbox for nanoscopy, spectroscopy, nano-optical quantum control and nanolithography., Nanoantennas: near-field light spectrum controlled and probed The sharp tip of an atomic force microscope (AFM) has helped researchers develop a new technique for manipulating light-sensitive nanoantennas. Recent studies have shown that engineering tiny gaps between surface-bound gold nanorods is an effective way to focus optical radiation and convert it into locally concentrated energy. Researchers in China have now used an AFM tip to position a semiconductor quantum dot into the gap between two gold nanorods, and controlled and read out the spectrum of the localized energy. When the nanoantenna is exposed to a linearly polarized light, the gap hosts a hot spot with a Lorentz-type spectrum, and the quantum dot is excited. An elliptically polarized light, on the other hand, turns the hot spot into a cold spot with a Fano-type spectrum, and the quantum dot is shielded from light exposure.

Limited research effort in the Central Mediterranean deep sea has reported a lower species diversity in this area than in adjacent regions. With the recent advent of remotely operated underwater vehicles (ROVs), the deep sea has become more accessible to surveys, especially rocky benthic areas such as canyons and escarpments. The aim of the present study was to assess diversity, spatial and bathymetric distribution, density, habitat, and microhabitat associations of echinoderms in deep waters around the Maltese Islands. Video data were acquired through ROV surveys as part of the LIFE BaĦAR for N2K project, at depths of 216 to 1031 m. In total, 25 echinoderm taxa were recorded, including the first Central Mediterranean records of the sea stars Marginaster capreensis (Gasco, 1876) and Sclerasterias neglecta (Perrier, 1891), and the first record of the holothuroid Mesothuria intestinalis (Ascanius, 1805) from Maltese waters. Six species were observed deeper than their currently accepted depth range in the Mediterranean. The most abundant species were the crinoids Antedon mediterranea (Lamarck, 1816) and Leptometra phalangium (Muller, 1841), which formed very dense aggregations of up to 2900 individuals/1000 m2 in a small area to the south of Malta. This area also supports the only known Mediterranean population of the Atlantic sea star Coronaster briareus (Verrill, 1882). Bathymetric distribution varied for each species, and the overall echinoderm diversity seemed stable across the surveyed depths. Since previous deep-sea studies in the area were based on trawling surveys, many deep-sea echinoderm species are reported in the literature as occurring on sedimentary bottoms. However, the present study revealed that several occur more often on rocky substrata, corals, or anthropogenic objects than on sediments. Our study based on video footage also provided insights into the microhabitat of many deep-sea species, yielding information that is not obtainable through remote sampling.

Both subthalamic nucleus (STN) and caudal zona incerta (cZI) have been implicated as the optimal locus for deep brain stimulation (DBS) in Parkinson’s disease (PD). We present a retrospective clinico-anatomical analysis of outcomes from DBS targeting both STN and cZI. Forty patients underwent bilateral DBS using an image-verified implantable guide tube/stylette technique. Contacts on the same quadripolar lead were placed in both STN and cZI. After pulse generator programming, contacts yielding the best clinical effect were selected for chronic stimulation. OFF-medication unified PD rating scale (UPDRS) part III scores pre-operatively and ON-stimulation at 1–2 year follow up were compared. Active contacts at follow-up were anatomically localised from peri-operative imaging. Overall, mean UPDRS part III score improvement was 55 ± 9% (95% confidence interval), with improvement in subscores for rigidity (59 ± 13%), bradykinesia (58 ± 13%), tremor (71 ± 24%) and axial features (36 ± 19%). Active contacts were distributed in the following locations: (1) within posterior/dorsal STN (50%); (2) dorsal to STN (24%); (3) in cZI (21%); and (4) lateral to STN (5%). When contacts were grouped by location, no significant differences between groups were seen in baseline or post-operative improvement in contralateral UPDRS part III subscores. We conclude that when both STN and cZI are targeted, active contacts are distributed most commonly within and immediately dorsal to STN. In a subgroup of cases, cZI contacts were selected for chronic stimulation in preference. Dual targeting of STN and cZI is feasible and may provide extra benefit compared with conventional STN DBS is some patients.

The sea star Coronaster briareus (Verrill Am J Sci (Ser III), 1882) is reported for the first time from the Mediterranean Sea. A total of 26 individuals were sighted in Maltese waters during ROV surveys made in July 2015 and June–July 2016. The identity of the species was confirmed through morphological examination of a specimen collected in June 2016. This identification is discussed in the light of inconsistencies in the published descriptions of species of Coronaster recorded from the Atlantic, and of individuals belonging to this genus recorded from the eastern Atlantic and whose coloration does not match that of C. briareus or C. volsellatus (the only species of Coronaster hitherto known from the Atlantic). The presence of numerous individuals of C. briareus in Maltese waters, recorded on two occasions a year apart over a relatively large area, indicates that there is an established population. This represents a considerable expansion of the distribution range of this species, which is mostly known from the western Atlantic. Possible reasons for its presence in Maltese waters are discussed, but the dynamics of the occurrence of C. briareus in the central Mediterranean remain unknown., peer-reviewed

Plasmon–emitter hybrid nanocavity systems exhibit strong plasmon–exciton interactions at the single-emitter level, showing great potential as testbeds and building blocks for quantum optics and informatics. However, reported experiments involve only one addressable emitting site, which limits their relevance for many fundamental questions and devices involving interactions among emitters. Here we open up this critical degree of freedom by demonstrating selective far-field excitation and detection of two coupled quantum dot emitters in a U-shaped gold nanostructure. The gold nanostructure functions as a nanocavity to enhance emitter interactions and a nanoantenna to make the emitters selectively excitable and detectable. When we selectively excite or detect either emitter, we observe photon emission predominantly from the target emitter with up to 132-fold Purcell-enhanced emission rate, indicating individual addressability and strong plasmon–exciton interactions. Our work represents a step towards a broad class of plasmonic devices that will enable faster, more compact optics, communication and computation., Plasmonic nanostructures can tailor excitation and emission for quantum emitters, but generally only for a single emitter. In this work, the authors selectively excite and detect one out of two quantum dots coupled to a deep-subwavelength cavity composed of three gold nanorods assembled into a U-shape.

Sublittoral pebble beds are generally considered to be impoverished, but the physical and biological characteristics of these habitats are poorly known. We characterised nineteen pebble bed sites in the Maltese Islands, providing detailed habitat data for Mediterranean sublittoral pebble beds for the first time. Nearly 40,000 individuals belonging to 332 taxa were recorded in all, with total richness estimated to reach 440 taxa; molluscs, crustaceans and polychaetes were the most diverse faunal groups. This high diversity is likely due to the structural complexity of the pebble beds, which had a vertically stratified arrangement of sediment particles that is likely maintained through periodic physical disturbance. Variation in the biotic assemblage from site to site was correlated with changes in the quantity of sand and silt, with the area of the pebble bed, with water depth, and with the thickness of the pebble layer. This indicates that pebble-bed macrofaunal assemblages are sensitive to changes in hydrodynamic conditions and sediment loading, to alterations to the stratification of the pebble beds, and to fragmentation of the habitat patches. These results contradict assertions that sublittoral pebble beds are impoverished, instead showing that they can be highly diverse habitats supporting biotic assemblages that respond to a complex set of environmental variables. The present findings enable better understanding of the ecological importance of pebble beds and of the potential impacts of anthropogenic disturbance, enabling more informed decisions for habitat conservation and management.

Manipulating large numbers of a variety of particles/wires is essential for many lab-on-a-chip technologies. Here we generate a planar array of optofluidic vortices with photothermal gradients from an easy-fabricated graphene oxide (GO) heater to achieve high-throughput and multiform manipulation at low excitation power and low loss. As a tweezer, each vortex can rapidly capture and confine particles without restrictions on shapes and materials. The stiffness of the confinement is easily tuned by adjusting the vortex dimension. As a motor, it can actuate any traps to persistently rotate/spin in clockwise or anti-clockwise mode. As a high-performance ‘workshop’, this work lays the groundwork for various self-assembly ranging from colloid-based clusters, chains, capsules, shells and ultra-thin films, through particles’ surface modification and fusion, to nanowire-based architectures. Furthermore, we can create multiple vortex arrays through fabricating an array of heaters, which enables massively parallel manipulation and distributed operations all on a chip. A lab-on-a-chip device can capture, contain and self-assemble large numbers of microparticles with innovative liquid vortex technology. Sailing He from Sweden's Royal Institute of Technology and co-workers in China developed a platform that uses graphene oxide ‘heaters’, activated by lasers, to alter the surface tension of nearby liquid droplets. This effect, known as thermocapillary convection, produces whirlpool-like spinning forces with a trapping power determined by droplet geometry. To demonstrate the potential of this approach, the team fabricated a microfluidic device featuring parallel arrays of vortices. Examples include precise control over materials, such as silver nanowires, that are difficult to handle with optical tweezers; a spinning quad-core motor providing persistent torque; and a ‘workshop’ for self-assembly that combines tweezer and motor functions to organize polystyrene particles into linear-, block- and triangle-shaped complexes. Planar arrays of optofluidic vortices are generated with photothermal gradients from an array of graphene oxide heaters to achieve multiform manipulations. As a tweezer, each vortex can rapidly capture and confine particles without any restriction on shapes or materials. As a motor, it can actuate any trapped particle to persistently rotate/spin in clockwise or anti-clockwise mode. Such a high-performance ‘workshop’ can be used for various self-assembly ranging from colloid-based clusters, chains, capsules, shells, and ultra-thin films, through particles’ surface modification and fusion, to nanowires-based architectures.

Analysis of macro-and micronutrient content of leaves ofGmelina arborea, a deciduous tree widely planted in the lowland tropics, was undertaken to determine the effects of leaf position within the crown and leaf age in relation to time of flushing on foliar nutrient levels. Within the crown, foliar nitrogen, phosphorus, zinc, and boron levels decreased, and calcium and iron levels increased, with increasing amount of leaf shading. Evidence of a genuine trend of declining nitrogen and potassium levels with increasing leaf ‘age’ is presented, the fact of which will greatly complicate sampling procedures.