Showing papers by "National Institute of Advanced Industrial Science and Technology published in 2017"

Metal–organic frameworks meet metal nanoparticles: synergistic effect for enhanced catalysis

Abstract: Metal–organic frameworks (MOFs), established as a relatively new class of crystalline porous materials with high surface area, structural diversity, and tailorability, attract extensive interest and exhibit a variety of applications, especially in catalysis. Their permanent porosity enables their inherent superiority in confining guest species, particularly small metal nanoparticles (MNPs), for improved catalytic performance and/or the expansion of reaction scope. This is a rapidly developing interdisciplinary research field. In this review, we provide an overview of significant progress in the development of MNP/MOF composites, including various preparation strategies and characterization methods as well as catalytic applications. Special emphasis is placed on synergistic effects between the two components that result in an enhanced performance in heterogeneous catalysis. Finally, the prospects of MNP/MOF composites in catalysis and remaining issues in this field have been indicated.

Neuromorphic computing with nanoscale spintronic oscillators

Abstract: Neurons in the brain behave as nonlinear oscillators, which develop rhythmic activity and interact to process information. Taking inspiration from this behaviour to realize high-density, low-power neuromorphic computing will require very large numbers of nanoscale nonlinear oscillators. A simple estimation indicates that to fit 108 oscillators organized in a two-dimensional array inside a chip the size of a thumb, the lateral dimension of each oscillator must be smaller than one micrometre. However, nanoscale devices tend to be noisy and to lack the stability that is required to process data in a reliable way. For this reason, despite multiple theoretical proposals and several candidates, including memristive and superconducting oscillators, a proof of concept of neuromorphic computing using nanoscale oscillators has yet to be demonstrated. Here we show experimentally that a nanoscale spintronic oscillator (a magnetic tunnel junction) can be used to achieve spoken-digit recognition with an accuracy similar to that of state-of-the-art neural networks. We also determine the regime of magnetization dynamics that leads to the greatest performance. These results, combined with the ability of the spintronic oscillators to interact with each other, and their long lifetime and low energy consumption, open up a path to fast, parallel, on-chip computation based on networks of oscillators.

An atlas of human long non-coding RNAs with accurate 5′ ends

Abstract: Long non-coding RNAs (lncRNAs) are largely heterogeneous and functionally uncharacterized. Here, using FANTOM5 cap analysis of gene expression (CAGE) data, we integrate multiple transcript collections to generate a comprehensive atlas of 27,919 human lncRNA genes with high-confidence 5' ends and expression profiles across 1,829 samples from the major human primary cell types and tissues. Genomic and epigenomic classification of these lncRNAs reveals that most intergenic lncRNAs originate from enhancers rather than from promoters. Incorporating genetic and expression data, we show that lncRNAs overlapping trait-associated single nucleotide polymorphisms are specifically expressed in cell types relevant to the traits, implicating these lncRNAs in multiple diseases. We further demonstrate that lncRNAs overlapping expression quantitative trait loci (eQTL)-associated single nucleotide polymorphisms of messenger RNAs are co-expressed with the corresponding messenger RNAs, suggesting their potential roles in transcriptional regulation. Combining these findings with conservation data, we identify 19,175 potentially functional lncRNAs in the human genome.

Oil/water separation techniques: a review of recent progresses and future directions

Abstract: Oil/water separation is a field of high significance as it has direct practical implications for resolving the problem of industrial oily wastewater and other oil/water pollution. Therefore, the development of functional materials for efficient treatment of oil-polluted water is imperative. In this feature article, we have reviewed the recent progress of oil/water separation technologies based on filtration and absorption methods using various materials that possess surface superwetting properties. In each section, we present in detail representative work and describe the concepts, employed materials, fabrication methods, and the effects of their wetting/dewetting behaviors on oil/water separation. Finally, the challenges and future research directions of this promising research field are briefly discussed.

MoS2 monolayer catalyst doped with isolated Co atoms for the hydrodeoxygenation reaction

Abstract: The conversion of oxygen-rich biomass into hydrocarbon fuels requires efficient hydrodeoxygenation catalysts during the upgrading process. However, traditionally prepared CoMoS2 catalysts, although efficient for hydrodesulfurization, are not appropriate due to their poor activity, sulfur loss and rapid deactivation at elevated temperature. Here, we report the synthesis of MoS2 monolayer sheets decorated with isolated Co atoms that bond covalently to sulfur vacancies on the basal planes that, when compared with conventionally prepared samples, exhibit superior activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene. This higher activity allows the reaction temperature to be reduced from the typically used 300 °C to 180 °C and thus allows the catalysis to proceed without sulfur loss and deactivation. Experimental analysis and density functional theory calculations reveal a large number of sites at the interface between the Co and Mo atoms on the MoS2 basal surface and we ascribe the higher activity to the presence of sulfur vacancies that are created local to the observed Co–S–Mo interfacial sites. Converting oxygen-rich biomass into fuels requires the removal of oxygen groups through hydrodeoxygenation. MoS2 monolayer sheets decorated with isolated Co atoms bound to sulfur vacancies in the basal plane have now been synthesized that exhibit superior catalytic activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene when compared to conventionally prepared materials.

Solar cell efficiency tables (version 49)

Abstract: Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since June 2016 are reviewed. URI: http://onlinelibrary.wiley.com/doi/10.1002/pip.2855/abstract [1] Authors: GREEN Martin A. EMERY Keith HISHIKAWA Y. WARTA W. DUNLOP Ewan LEVI Dean HO-BAILLIE Anita Publication Year: 2017 Science Areas: Energy and transport [2]

Key Findings of the World’s First Offshore Methane Hydrate Production Test off the Coast of Japan: Toward Future Commercial Production

Abstract: Marine methane hydrate in sands has huge potential as an unconventional gas resource; however, no field test of their production potential had been conducted. Here, we report the world’s first offshore methane hydrate production test conducted at the eastern Nankai Trough and show key findings toward future commercial production. Geological analysis indicates that hydrate saturation reaches 80% and permeability in the presence of hydrate ranges from 0.01 to 10 mdarcies. Permeable (1–10 mdarcies) highly hydrate-saturated layers enable depressurization-induced gas production of approximately 20,000 Sm3/D with water of 200 m3/D. Numerical analysis reveals that the dissociation zone expands laterally 25 m at the front after 6 days. Gas rate is expected to increase with time, owing to the expansion of the dissociation zone. It is found that permeable highly hydrate-saturated layers increase the gas–water ratio of the production fluid. The identification of such layers is critically important to increase the en...

Learning Spatio-Temporal Features with 3D Residual Networks for Action Recognition

Abstract: Convolutional neural networks with spatio-temporal 3D kernels (3D CNNs) have an ability to directly extract spatiotemporal features from videos for action recognition. Although the 3D kernels tend to overfit because of a large number of their parameters, the 3D CNNs are greatly improved by using recent huge video databases. However, the architecture of3D CNNs is relatively shallow against to the success of very deep neural networks in 2D-based CNNs, such as residual networks (ResNets). In this paper, we propose a 3D CNNs based on ResNets toward a better action representation. We describe the training procedure of our 3D ResNets in details. We experimentally evaluate the 3D ResNets on the ActivityNet and Kinetics datasets. The 3D ResNets trained on the Kinetics did not suffer from overfitting despite the large number of parameters of the model, and achieved better performance than relatively shallow networks, such as C3D. Our code and pretrained models (e.g. Kinetics and ActivityNet) are publicly available at https://github.com/kenshohara/3D-ResNets.

High-Performance Energy Storage and Conversion Materials Derived from a Single Metal-Organic Framework/Graphene Aerogel Composite.

Abstract: Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoOx) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoOx/NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon–graphene composite electrode (d...

A magnetic heterostructure of topological insulators as a candidate for an axion insulator

Abstract: An engineered topological insulator-based heterostructure is reported to show transport properties consistent with the realization of an axion insulator.

Particulate Photocatalyst Sheets Based on Carbon Conductor Layer for Efficient Z-Scheme Pure-Water Splitting at Ambient Pressure.

Abstract: Development of sunlight-driven water splitting systems with high efficiency, scalability, and cost-competitiveness is a central issue for mass production of solar hydrogen as a renewable and storable energy carrier. Photocatalyst sheets comprising a particulate hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) embedded in a conductive thin film can realize efficient and scalable solar hydrogen production using Z-scheme water splitting. However, the use of expensive precious metal thin films that also promote reverse reactions is a major obstacle to developing a cost-effective process at ambient pressure. In this study, we present a standalone particulate photocatalyst sheet based on an earth-abundant, relatively inert, and conductive carbon film for efficient Z-scheme water splitting at ambient pressure. A SrTiO3:La,Rh/C/BiVO4:Mo sheet is shown to achieve unassisted pure-water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency (STH) of 1.2% at 331 K a...

Light-driven liquid metal nanotransformers for biomedical theranostics.

Abstract: Room temperature liquid metals (LMs) represent a class of emerging multifunctional materials with attractive novel properties. Here, we show that photopolymerized LMs present a unique nanoscale capsule structure characterized by high water dispersibility and low toxicity. We also demonstrate that the LM nanocapsule generates heat and reactive oxygen species under biologically neutral near-infrared (NIR) laser irradiation. Concomitantly, NIR laser exposure induces a transformation in LM shape, destruction of the nanocapsules, contactless controlled release of the loaded drugs, optical manipulations of a microfluidic blood vessel model and spatiotemporal targeted marking for X-ray-enhanced imaging in biological organs and a living mouse. By exploiting the physicochemical properties of LMs, we achieve effective cancer cell elimination and control of intercellular calcium ion flux. In addition, LMs display a photoacoustic effect in living animals during NIR laser treatment, making this system a powerful tool for bioimaging.

High-quality monolayer superconductor NbSe 2 grown by chemical vapour deposition

Abstract: The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications. Currently, the growth of superconducting monolayers can only occur under ultrahigh vacuum and on specific lattice-matched or dangling bond-free substrates, to minimize environment- and substrate-induced disorders/defects. Such severe growth requirements limit the exploration of novel two-dimensional superconductivity and related nanodevices. Here we demonstrate the experimental realization of superconductivity in a chemical vapour deposition grown monolayer material—NbSe2. Atomic-resolution scanning transmission electron microscope imaging reveals the atomic structure of the intrinsic point defects and grain boundaries in monolayer NbSe2, and confirms the low defect concentration in our high-quality film, which is the key to two-dimensional superconductivity. By using monolayer chemical vapour deposited graphene as a protective capping layer, thickness-dependent superconducting properties are observed in as-grown NbSe2 with a transition temperature increasing from 1.0 K in monolayer to 4.56 K in 10-layer. Two-dimensional superconductors will likely have applications not only in devices, but also in the study of fundamental physics. Here, Wang et al. demonstrate the CVD growth of superconducting NbSe2 on a variety of substrates, making these novel materials increasingly accessible.

Atomically Dispersed Fe/N-Doped Hierarchical Carbon Architectures Derived from a Metal–Organic Framework Composite for Extremely Efficient Electrocatalysis

Abstract: Hierarchical graphitic porous carbon architectures with atomically dispersed Fe and N doping have been fabricated from a metal–organic framework (MOF) composite by using a facile strategy, which show high specific surface areas, hierarchical pore structures with macro/meso/micro multimodal pore size distributions, abundant surface functionality with single-atom dispersed N and Fe doping, and improved hydrophilicity. Detailed analyses unambiguously disclosed the main active sites of doped N atoms and FeNx species in the catalyst. The resultant catalyst affords high catalytic performance for oxygen reduction, outperforming the benchmark Pt catalyst and many state-of-the-art noble-metal-free catalysts in alkaline media, particularly in terms of the onset and half-wave potentials and durability. Such catalytic performance demonstrates the significant advantages of the unique hierarchical porous structure with efficient atomic doping, which provides a high density of accessible active sites for much improved m...

A reversible lithium–CO2 battery with Ru nanoparticles as a cathode catalyst

Abstract: Li–CO2 batteries have attracted wide attention owing to their high energy density and ability to utilize carbon dioxide. However, current Li–CO2 batteries still suffer from several unresolved problems such as low coulombic efficiency and high charge potential, and hence much work is still required to optimize the electrochemical performance of Li–CO2 batteries. In this work, Ru nanoparticles have been deposited on Super P carbon using a solvothermal method and the resulting material (Ru@Super P) has been employed as a cathode in Li–CO2 batteries. The Li–CO2 battery with Ru@Super P as the cathode exhibits significantly reduced charge potential and can be operated for 80 cycles with a fixed capacity of 1000 mA h g−1 at 100 mA g−1, which is by far the best cycling stability among the reported Li–CO2 batteries. We found that Ru possesses a selective catalytic activity in promoting the reaction between Li2CO3 and carbon during charge. This characteristic of Ru helps to avoid electrolyte decomposition and improve the electrochemical performance of Li–CO2 batteries.

The Apostasia genome and the evolution of orchids

Abstract: Constituting approximately 10% of flowering plant species, orchids (Orchidaceae) display unique flower morphologies, possess an extraordinary diversity in lifestyle, and have successfully colonized almost every habitat on Earth. Here we report the draft genome sequence of Apostasia shenzhenica, a representative of one of two genera that form a sister lineage to the rest of the Orchidaceae, providing a reference for inferring the genome content and structure of the most recent common ancestor of all extant orchids and improving our understanding of their origins and evolution. In addition, we present transcriptome data for representatives of Vanilloideae, Cypripedioideae and Orchidoideae, and novel third-generation genome data for two species of Epidendroideae, covering all five orchid subfamilies. A. shenzhenica shows clear evidence of a whole-genome duplication, which is shared by all orchids and occurred shortly before their divergence. Comparisons between A. shenzhenica and other orchids and angiosperms also permitted the reconstruction of an ancestral orchid gene toolkit. We identify new gene families, gene family expansions and contractions, and changes within MADS-box gene classes, which control a diverse suite of developmental processes, during orchid evolution. This study sheds new light on the genetic mechanisms underpinning key orchid innovations, including the development of the labellum and gynostemium, pollinia, and seeds without endosperm, as well as the evolution of epiphytism; reveals relationships between the Orchidaceae subfamilies; and helps clarify the evolutionary history of orchids within the angiosperms.

Vowel recognition with four coupled spin-torque nano-oscillators

Abstract: Substantial evidence indicates that the brain uses principles of non-linear dynamics in neural processes, providing inspiration for computing with nanoelectronic devices. However, training neural networks composed of dynamical nanodevices requires finely controlling and tuning their coupled oscillations. In this work, we show that the outstanding tunability of spintronic nano-oscillators can solve this challenge. We successfully train a hardware network of four spin-torque nano-oscillators to recognize spoken vowels by tuning their frequencies according to an automatic real-time learning rule. We show that the high experimental recognition rates stem from the high frequency tunability of the oscillators and their mutual coupling. Our results demonstrate that non-trivial pattern classification tasks can be achieved with small hardware neural networks by endowing them with non-linear dynamical features: here, oscillations and synchronization. This demonstration is a milestone for spintronics-based neuromorphic computing.

Performances and emission characteristics of NH3–air and NH3CH4–air combustion gas-turbine power generations

Abstract: For the first time, NH 3 –air combustion power generation has been successfully realized using a 50 kW class micro gas turbine system at the National Institute of Advanced Industrial Science and Technology (AIST), Japan. Based on the global demand for carbon-free power generation as well as recent advances involving gas-turbine technologies, such as heat-regenerative cycles, rapid fuel mixing using strong swirling flows, and NO x reduction using selective catalytic reduction (SCR), allow us to realize NH 3 –air combustion gas-turbine system, which was abandoned in the 1960′s. In the present system, the combustor adopted gaseous NH 3 fuel and diffusion combustion to enhance flame stability. The NH 3 pre-cracking apparatus for combustion enhancement using generated H 2 was not employed. The NH 3 –air combustion gas-turbine power generation system can be operated over a wide range of power and rotational speeds, i.e., 18.4 kW to 44.4 kW and 70,000 rpm to 80,000 rpm, respectively. The combustion efficiency of the NH 3 –air gas turbine ranged from 89% to 96% at 80,000 rpm. The emission of NO and unburnt NH 3 depends on the combustor inlet temperature. Emission data indicates that there are NH 3 fuel-rich and fuel-lean regions in the primary combustion zone. It is presumed that unburnt NH 3 is released from the fuel-rich region, while NO is released from the fuel-lean region. When diluted air enters the secondary combustion zone, unburnt NH 3 is expected to react with NO through selective non-catalytic reduction (SNCR). NH 3 CH 4 –air combustion operation tests were also performed and the results show that the increase of the NH 3 fuel ratio significantly increases the NO emission, whereas it decreases the NO conversion ratio. To achieve low NO x combustion in NH 3 –air combustion gas turbines, it is suggested to burn large quantities of NH 3 fuel and produce both rich and lean fuel mixtures in the primary combustion zone.

Metal-Nanoparticle-Catalyzed Hydrogen Generation from Formic Acid

Abstract: ConspectusTo meet the ever-increasing energy demand, the development of effective, renewable, and environmentally friendly sources of alternative energy is imperative Hydrogen (H2) is a renewable, clean energy carrier, which exhibits a threefold energy density compared to gasoline; H2 is considered one of the most promising alternative energy carriers for enabling a secure, clean energy future However, the realization of a hydrogen economy is restricted by several unresolved issues Particularly, one of the most difficult challenges is the development of a safe, efficient hydrogen storage and delivery system To this end, hydrogen storage techniques based on liquid-phase chemical hydrogen storage materials have become an attractive choiceFormic acid (FA) with a high volumetric capacity of 53 g H2/L demonstrates promise as a safe, convenient liquid hydrogen carrier However, generating H2 from FA in a controlled manner at ambient temperature is still challenging, which primarily depends on the catalyst

Tunable room-temperature single-photon emission at telecom wavelengths from sp3 defects in carbon nanotubes

Abstract: Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, present in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Single-photon emission deep into the centre of the telecom C band (1.55 µm) is achieved at the largest nanotube diameters we explore (0.936 nm). Single-photon emission with 99% purity is generated from sp3 defects in carbon nanotubes (CNTs) by optical excitation at room temperature. By increasing the CNT diameter from 0.76 nm to 0.94 nm, the emission wavelength can be changed from 1,100 nm to 1,600 nm.

Evidence and mechanism of efficient thermally activated delayed fluorescence promoted by delocalized excited states

Abstract: The design of organic compounds with nearly no gap between the first excited singlet (S1) and triplet (T1) states has been demonstrated to result in an efficient spin-flip transition from the T1 to S1 state, that is, reverse intersystem crossing (RISC), and facilitate light emission as thermally activated delayed fluorescence (TADF). However, many TADF molecules have shown that a relatively appreciable energy difference between the S1 and T1 states (~0.2 eV) could also result in a high RISC rate. We revealed from a comprehensive study of optical properties of TADF molecules that the formation of delocalized states is the key to efficient RISC and identified a chemical template for these materials. In addition, simple structural confinement further enhances RISC by suppressing structural relaxation in the triplet states. Our findings aid in designing advanced organic molecules with a high rate of RISC and, thus, achieving the maximum theoretical electroluminescence efficiency in organic light-emitting diodes.

Anomaly Detection for a Water Treatment System Using Unsupervised Machine Learning

Abstract: In this paper, we propose and evaluate the application of unsupervised machine learning to anomaly detection for a Cyber-Physical System (CPS). We compare two methods: Deep Neural Networks (DNN) adapted to time series data generated by a CPS, and one-class Support Vector Machines (SVM). These methods are evaluated against data from the Secure Water Treatment (SWaT) testbed, a scaled-down but fully operational raw water purification plant. For both methods, we first train detectors using a log generated by SWaT operating under normal conditions. Then, we evaluate the performance of both methods using a log generated by SWaT operating under 36 different attack scenarios. We find that our DNN generates fewer false positives than our one-class SVM while our SVM detects slightly more anomalies. Overall, our DNN has a slightly better F measure than our SVM. We discuss the characteristics of the DNN and one-class SVM used in this experiment, and compare the advantages and disadvantages of the two methods.

Bimetallic Metal–Organic Frameworks for Gas Storage and Separation

Abstract: Emerging as a new family of hybrid crystalline materials, bimetallic porous metal–organic frameworks (MOFs) have received great attention in gas storage and separation. We present a critical perspective on the construction of bimetallic MOFs, involving one-step synthesis and postsynthetic modification, and their applications in gas storage and separation. In particular, several examples of bimetallic MOFs have been provided to better understand of why such MOFs are so unique for these applications. We hope that the present perspective will inspire chemists working in this area to rationally design/develop new bimetallic MOFs for advanced applications.

Tin-Vacancy Quantum Emitters in Diamond.

Abstract: Tin-vacancy ($\mathrm{Sn}\text{\ensuremath{-}}V$) color centers were created in diamond via ion implantation and subsequent high-temperature annealing up to $2100\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ at 7.7 GPa. The first-principles calculation suggested that a large atom of tin can be incorporated into a diamond lattice with a split-vacancy configuration, in which a tin atom sits on an interstitial site with two neighboring vacancies. The $\mathrm{Sn}\text{\ensuremath{-}}V$ center showed a sharp zero phonon line at 619 nm at room temperature. This line split into four peaks at cryogenic temperatures, with a larger ground state splitting ($\ensuremath{\sim}850\text{ }\text{ }\mathrm{GHz}$) than that of color centers based on other group-IV elements, i.e., silicon-vacancy ($\mathrm{Si}\text{\ensuremath{-}}V$) and germanium-vacancy ($\mathrm{Ge}\text{\ensuremath{-}}V$) centers. The excited state lifetime was estimated, via Hanbury Brown--Twiss interferometry measurements on single $\mathrm{Sn}\text{\ensuremath{-}}V$ quantum emitters, to be $\ensuremath{\sim}5\text{ }\text{ }\mathrm{ns}$. The order of the experimentally obtained optical transition energies, compared with those of $\mathrm{Si}\text{\ensuremath{-}}V$ and $\mathrm{Ge}\text{\ensuremath{-}}V$ centers, was in good agreement with the theoretical calculations.

Hysteresis-free perovskite solar cells made of potassium-doped organometal halide perovskite

Abstract: Potassium-doped organometal halide perovskite solar cells (PSCs) of more than 20% power conversion efficiency (PCE) without I-V hysteresis were constructed. The crystal lattice of the organometal halide perovskite was expanded with increasing of the potassium ratio, where both absorption and photoluminescence spectra shifted to the longer wavelength, suggesting that the optical band gap decreased. In the case of the perovskite with the 5% K+, the conduction band minimum (CBM) became similar to the CBM level of the TiO2-Li. In this situation, the electron transfer barrier at the interface between TiO2-Li and the perovskite was minimised. In fact, the transient current rise at the maximum power voltages of PSCs with 5% K+ was faster than that without K+. It is concluded that stagnation-less carrier transportation could minimise the I-V hysteresis of PSCs.