Simple Units Research Articles

Magnetothermal Shape‐Morphing of Thermoset Structures

AbstractShape‐morphing of thermosets is challenging due to their permanently cross‐linked polymer network structure. Here, a magnetothermal shape‐morphing strategy is proposed for complex thermoset structures via reshaping, assembly, and shape memory. The thermoset composite is fabricated by adding magnetic nanoparticles into dynamically cross‐linked thermoset resin, which imparts magnetothermal effect and reprocessability under an alternating magnetic field. Epoxy composites are prepared with various weight fractions of Fe3O4 nanoparticles, and their magnetothermal and thermomechanical properties are studied. For a composite with 15 wt% Fe3O4 nanoparticles, the glass transition temperature Tg is 62 °C, and the topology freezing transition temperature Tv is 175 °C. An alternating magnetic field with a working power of 2000 W can generate a temperature of 156 °C, enabling bond exchange reactions and stress relaxation in the dynamically cross‐linked epoxy resin. Magnetothermal reshaping and bonding facilitate the assembly of complex‐shaped structures from simple units, while magnetothermal shape memory provides rapid actuation deformation responses within 60 s. Various examples of magnetothermal shape‐morphing of complex thermoset structures, including grasper, origami, and octopus‐inspired functional structures, are demonstrated. The results indicate that the present shape‐morphing strategy provides advantages such as remote control, high efficiency, flexible design, and straightforward structural fabrication.

Single snapshot-based miniaturized mid-infrared spectrometer with a dielectric metasurface

Mid-infrared spectroscopy is critical for applications like environmental monitoring and medical diagnostics, as it includes the fundamental vibrational frequencies of many molecular bonds, enabling detailed chemical analysis. We developed a miniature mid-infrared spectrometer using a fully dielectric metasurface operating in the 3–5 µm range. By combining simple structural units, design flexibility was enhanced, resulting in rich spectral data. The spectrometer was evaluated using narrowband, broadband, and transmission spectra of real materials. We detected the spectral responses of metasurface arrays and determined the unknown spectrum using an algorithm based on Tikhonov regularization with generalized cross-validation. By reconstructing multiple narrow spectra obtained through rotating the filters, spectral resolution intervals of approximately 10 nm were achieved.

SCGC : Self-supervised contrastive graph clustering

Graph clustering discovers groups or communities within networks. Increasingly, models use autoencoders to achieve effective clustering combined with Graph Neural Networks (GNN) for structure incorporation. However, GNNs based on convolution or attention variants lack dynamic fusion, suffer from over-smoothing, noise, node heterophily, are computationally expensive and typically require the complete graph being present. Instead, we propose SCGC, capable of dynamic soft structure fusion via augmentation-less edge-contrastive loss. Further, we propose SCGC*, with a more expressive novel distance metric, Influence, and our Influence Augmented Contrastive (IAC) loss, requiring only half the model parameters. Our models, SCGC and SCGC*, dynamically fuse discriminative node representations, jointly refine soft cluster assignments, completely eliminate convolutions and attention of traditional GNNs, use only simple linear units, and yet efficiently incorporate structure. They are impervious to layer depth; robust to over-smoothing, incorrect edges and heterophily; scalable by batching; augmentation-less; relaxes the homophily assumption and trivially parallelizable. We improve significantly over the state-of-the-art on a wide range of benchmarks, including images, sensor data, text, and citation networks, with superb efficiency. Specifically, 20% on ARI and 18% on NMI for DBLP; overall 55% reduction in training time and overall, 81% reduction on inference time. code: https://github.com/gayanku/SCGC.

Critical plasma-processing-enabled growth of chirality-predefined single-walled carbon nanotubes from carbon nanorings

The chirality-controlled growth of single-walled carbon nanotubes (SWNTs) has been an ultimate challenge since their discovery. We report a proof-of-principle plasma processing on the chirality-predefined growth of SWNTs originating from single-hoop molecules of carbon six-membered rings (carbon nanorings: CNRs), which can be viewed as simple units of (n, n) metallic SWNTs (n: the number of benzene rings). Plasma-enhanced chemical vapor deposition enables us to find the correlation between the diameter of CNRs and that of SWNTs over n = 6–12, while only the specified CNRs (n = 10, 12) correspondingly grow up to near (10,10) and (12,12) metallic SWNTs at critical low-temperature of 350 °C.

Composite suture material based on polylactide accelerates the healing of surgical wounds in in vivo experiment.

In laboratory conditions, composite sutures based on polylactide (PLA) containing chitin nanofibrils modified with polyethylene glycol (CN-PEG) and poviargol (silver nanoparticles stabilized with poly(N-vinylpyrrolidone)) were obtained, studied, and used as a prototype. Surgical sutures threads with the addition of CN-PEG have stable mechanical properties both in air and in a buffer simulating the environment of a living organism. The yield strength of oriented threads decreased by an average of 15%, whereas for non-oriented threads the decrease was 3-4 times. The strength values in simple units of unfilled PLA, PLA containing 5 wt % CN-PEG, and PLA with 1 wt % Poviargol were on average 50% higher than the national standard 31620-2012. The results of in vivo experiments on albino rats (cross-linking skin and muscle tissue in the linea alba area) showed that composite sutures are best for suturing muscle tissue, whereas unfilled PLA sutures are more suitable for suturing skin. When suturing muscle tissue, suturing with composite sutures increased the number of collagen fibers of different diameters.

Revealing the Role of Redox Reaction Selectivity and Mass Transfer in Current–Voltage Predictions for Ensembles of Photocatalysts

Photocatalysts are conceptually simple reaction units where nanoscale semiconductors integrated with catalysts drive a pair of redox reactions on illumination. However, the proximity of reaction sites performing cathodic and anodic reactions poses dire challenges to realize large light-to-fuel conversion efficiencies. In this study, a powerful, yet straightforward, equivalent-circuit detail-balance modeling framework is developed and applied to evaluate the performance of photocatalytic systems featuring multiple light absorbers. Specifically, low bandgap iridium-doped strontium titanate is modeled a Z-scheme photocatalyst to effect desired hydrogen evolution and iron-based redox shuttle oxidation reactions. Our model has unique capabilities to simulate competing redox reactions and address mass-transfer limitations. In a significant departure from state-of-the-art circuit models, our study develops tools to perform load-line analyses by incorporating a net electrochemical load curve that includes both desired and competing redox reactions. Consequently, reaction selectivity is predicted from equivalent circuit models for photocatalytic and photoelectrochemical systems. Our investigation into ensembles comprised of multiple, semi-transparent light absorbers reveals their potential to outperform a single, optically thick light absorber, particularly when operated under mass-transfer-limited conditions. However, this outcome hinges on minimizing mass-transfer rates of select redox species to prevent undesired reactions of hydrogen oxidation and/or redox shuttle reduction. Our findings demonstrate that reaction selectivity can be achieved by tuning asymmetry in redox species mass-transfer even with perfectly symmetric electrocatalytic charge-transfer coefficients. The influences of various kinetic, mass-transfer, and thermodynamic parameters are explored to offer crucial insights to inform the next-generation of photocatalysts, selective coatings, and reactor designs.

Optimizing Active Layer Morphology of Organic Solar Cells by Constructing Random Copolymers with Simple Third Units.

The molecular structure of the polymer PM6 is elaborately modified through random copolymerization by incorporating simple units of either difluoro-substituted thiophene (2FT) or dicyano-substituted thiophene (2CNT). The incorporation of the 2FT unit significantly enhanced the coplanarity of the random copolymers, leading to improved molecular crystallinity, whereas the introduction of the 2CNT unit featured the opposite effect. Thanks to the optimized morphology resembling a fiber-like interpenetrating network structure, the organic solar cells based on PM6-10%2FT:IT4F showed higher and more balanced charge mobilities, achieving a power conversion efficiency (PCE) of 12.65%, which is comparable to that of PM6-based devices. For comparison, the 2CN-series random copolymers-based devices exhibited lower PCEs of ˂12%. Interestingly, a superior PCE close to 19.0% is achieved in PM6:L8-BO:PM6-20%2CN based ternary device due to the significant improvement in open-circuit voltage. This work demonstrates that the crystallinity of donor polymers can be enhanced by introducing simple structural units to strengthen the coplanarity of the backbone, thereby achieving an optimized morphology that promotes favorable charge transport.

Comprehensive assessment of rock glaciers in the Himachal Himalayas: Updated inventory and labelling

Rock glaciers are geomorphological features often used as a visible expression of mountain permafrost. These are creeping ice-debris with distinct ridge and furrow structures on the surface with a steep frontal slope. Rock glaciers, being the valuable past permafrost indicators, also have utmost hydrological significance in near future. Therefore, mapping of rock glaciers is an important step in order to understand permafrost regimes better. The Himalayas have large occurrences of these features and this study in Himachal Himalayas complied 789 rock glaciers, covering an area of about 336.2 km2. Different labels based on genesis, location, shape, form, surface relief and activity revealed rock glaciers were mainly derived from talus slopes (239) and exhibited tongue shape (377), primarily found in cirques (531). Most of them were classified as simple units (603) with well-developed surface relief (387), and they were found to be predominantly intact (760). The topographical parameters suggest majority of the rock glaciers are located between 4000 and 4800 m with mean elevation to be 4635 m. These rock glaciers are present at gentle to steep slope gradient (0 to 45°) with curvature ranging between −3.5 and 4.5, and majority showing convex curvature. The slope aspect conducive for formation of rock glaciers in Himachal is northerly (N, NW, NE). Principal geology for these rock glaciers belongs to slate, phyllite, quartzarenite, limestone and meta basics. The climatic parameters and indices also affect the rock glaciers occurrence significantly. The mean land surface temperature (LST) for majority rock glaciers lies between 0 and −15°C. While, the mean NDSI of all the rock glaciers varies from 0.04 to 0.68 and mean NDVI varies from −0.06 to 0.08. Overall, the inventory along with labels is a valuable database for understanding the distribution and characteristics of rock glaciers in the Himachal Himalayas.

A High-Performance Organic Photovoltaic System with Versatile Solution Processability.

Recently developed organic photovoltaic (OPV) materials have simultaneously closed the gaps in efficiency, stability, and cost for single-junction devices. Nonetheless, the developed OPV materials still pose big challenges in meeting the requirements for practical applications, especially regarding the prevalent issues of solution processability. Herein, a highly efficient polymer donor, named DP3, incorporating an electron-rich benzo[1,2-b:4,5-b']dithiophene unit as well as two similar and simple acceptor units is presented. Its primary objective is to enhance the interchain and/or intrachain interactions and ultimately fine-tune bulk-heterojunction microstructure. The DP3:L8-BO system demonstrates the highest power conversion efficiency (PCE) of 19.12%. This system also exhibits high-performance devices with over 18% efficiencies for five batches with various molecular weights (23.6-80.8KDa), six different blend thicknesses (95-308nm), differenced coating speeds (3.0-29.1mmin-1), with promising PCEs of 18.65% and 15.53% for toluene-processed small-area (0.029cm2) cells and large-area (15.40cm2) modules, thereby demonstrating versatile solution processability of the designed DP3:L8-BO system that is a strong candidate for commercial applications.

Effect of B2O3 on the viscosity, structure and crystalline phase of CaO–MgO–Al2O3–SiO2–MnO-based high alumina slags

The effects of B2O3 on viscosities, structures and phase transitions of CaO–MgO–Al2O3–SiO2–MnO-(0-8.0 wt%)B2O3 slags were investigated in this work. From the viscosity experimental results, the slag viscosities declined and the Eη decreased from 205.19 to 175.95 kJ/mol with the addition of B2O3 in slags from 0 to 8.0 wt%. From the structure analysis by using FTIR and XPS, B2O3 entered into the silicate network to increase the slag polymerization degree, while the formation of simple two-dimensional BO3 trihedral units could significantly decline the symmetry and stability of the structure. The effects of decreasing the network stability and forming low-melting eutectics were more dominated than the effects of increasing the structure polymerization degree, which could reduce the slag viscosity. Furthermore, adding B2O3 could decrease the slag initial precipitation temperature and change the primary crystal phase of the slag from melilite to spinel. The comprehensive effects of reducing the slag structure stability and decreasing the influence of solid phase on viscosity eventually resulted in the improvement of the slag fluidity.

Influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags for casting of high-Ti steel

In the current study, the influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags was discussed through the measurement of viscosity-temperature relationship, melting temperature, crystallization temperature, crystallization rate and phases, and Raman spectrum. With the substitution of SiO2 by TiO2 in slags from 0 % to 12 %, the viscosity at 1300 °C, the melting temperature and break temperature decreased and then increased, while those of slags with the substitution of CaO by BaO from 4 % to 16 % decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, crystallization phases gradually changed from cuspidine (Ca4Si2F2O7) to perovskite (CaTiO3), the initial and complete crystallization temperatures had the tendency to increase from 918 °C to 1260 °C and from 857 °C to 1139 °C, respectively, and the overall crystallization ability of slags increased. With the substitution of CaO by BaO from 4 % to 16 %, the initial and complete crystallization temperature of these slags decreased, and the overall crystalline ability decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, structural units changed from the simple units to complex units, but the transition was opposite with the substitution from 10 % to 12 %, which was related to the transition of TiO2 from basic oxide to amphoteric oxide. With the substitution of CaO by BaO from 4 % to 16 %, the degree of polymerization and the viscosity of theses slags decreased, which was related to the supplement of more active O2− ion from BaO. Hence, the excessive substitution of SiO2 by TiO2 under the steel-slag reaction would cause the increase of the slag viscosity and crystallization ability, while the substitution of CaO by BaO could weaken the variation of slag viscosity and crystallization ability.

Modelling effective thermal conductivity in polymer composites: A simple cubic structure approach

In this study, we propose the simple cubic model, a distinctive thermal-conductive mathematics for modelling the effective thermal conductivity in polymer composites, taking both filler size and interface thermal resistance into account. This model is constructed by delineating heat transport paths within simple cubic structural units, leveraging principles involving Fourier's law, minimum thermal resistance, specific equivalent thermal conductivity, and thermal resistance network. Demonstrating broad applicability, the simple cubic model accurately predicts effective thermal conductivity within a 0–40 % volume fraction range of filler in polymer composites, maintaining less than 15 % error. Its robustness is validated across over 100 experimental datasets, encompassing various polymer matrices and granular filler types. This extensive validation underscores the model's efficacy, both with our experimental data and existing literature. The simple cubic model's insightful predictions make it valuable in designing and preparing thermally conductive polymer composites.

VR interactive input system based on INS and binocular vision fusion

In virtual reality interactive input systems, real-time and accurate spatial position and pose measurement is key to achieving a natural user interface. This study explores the application of inertial measurement units and binocular vision fusion technology in virtual reality interactive input systems, with the aim of improving the tracking accuracy of the system through optimized pose models and visual algorithms. A virtual reality measurement technology that integrates inertial measurement units and binocular vision is proposed by using an improved Kalman filtering algorithm to process inertial measurement units data, and combining it with the SURF algorithm optimized binocular vision system. Experimental results showed that fusion technology could reduce sensor noise and bias, improve the accuracy of pose estimation, and promote stable and robust motion tracking in virtual reality systems. In the angle range of -90 ° to 90 °, the average absolute error of the fusion system compared to the simple inertial measurement units pose calculation decreased from 3.371 ° to 1.369 ° In the experiment of measuring distance with a binocular vision system, the average absolute error value decreased to 1.532 mm, and the error range of the marker within the distance range of 500 mm to 650 mm was controlled within -1.3 mm to 1.2 mm. This study provides an effective solution for achieving high-precision virtual reality interactive input systems and is meaningful for the advancement of virtual reality technology.

Synthesis, biological activities, and molecular docking studies of triazolo[4,3-b]triazine derivatives as a novel class of α-glucosidase and α-amylase inhibitors.

In diabetes mellitus, amylase and glucosidase enzymes are the primary triggers. The main function of these enzymes is to break macromolecules into simple sugar units, which directly affect blood sugar levels by increasing blood permeability. To overcome this metabolic effect, there is a need for a potent and effective inhibitor capable of suppressing the enzymatic conversion of sugar macromolecules into their smaller units. Herein, we reported the discovery of a series of substituted triazolo[4,3-b][1,2,4]triazine derivatives as α-glucosidase and α-amylase inhibitors. All target compounds demonstrated significant inhibitory activities against α-glucosidase and α-amylase enzymes compared with acarbose as the positive control. The most potent compound 10k, 2-[(6-phenyl-[1,2,4]triazolo[4,3-b][1,2,4]triazin-3-yl)thio]-N-[4-(trifluoromethyl)phenyl]acetamide, demonstrated IC50 values of 31.87 and 24.64 nM against α-glucosidase and α-amylase enzymes, respectively. To study their mechanism of action, kinetic studies were also done, which determined the mode of inhibition of both enzymes. Molecular docking was used to confirm the binding interactions of the most active compounds.

The evolution of embedded systems in automotive industry: A global review

The evolution of embedded systems in automotive industry: A global review

Modular tissue-in-a-CUBE platform to model blood-brain barrier (BBB) and brain interaction

With the advent of increasingly sophisticated organoids, there is growing demand for technology to replicate the interactions between multiple tissues or organs. This is challenging to achieve, however, due to the varying culture conditions of the different cell types that make up each tissue. Current methods often require complicated microfluidic setups, but fragile tissue samples tend not to fare well with rough handling. Furthermore, the more complicated the human system to be replicated, the more difficult the model becomes to operate. Here, we present the development of a multi-tissue chip platform that takes advantage of the modularity and convenient handling ability of a CUBE device. We first developed a blood-brain barrier-in-a-CUBE by layering astrocytes, pericytes, and brain microvascular endothelial cells in the CUBE, and confirmed the expression and function of important tight junction and transporter proteins in the blood-brain barrier model. Then, we demonstrated the application of integrating Tissue-in-a-CUBE with a chip in simulating the in vitro testing of the permeability of a drug through the blood-brain barrier to the brain and its effect on treating the glioblastoma brain cancer model. We anticipate that this platform can be adapted for use with organoids to build complex human systems in vitro by the combination of multiple simple CUBE units.

Linguocognitive Approach to Text Analysis

Cognitive sciences were officially included in the nomenclature of scientific specialties in Russia in 2021. However, the issue of the subject and method of cognitive science in general and its projection on text analysis in particular remains little known to the general scientific community. Linguistic text analysis has gone through several stages of evolution. Each of them accumulates the critical aspects highlighting the necessity to search for new approaches. There are three such approaches in linguistics: structural, communicative, cognitive. The structural paradigm made it possible to solve scientific problems using the example of simple language units. However, it was experiencing serious difficulties in studying complex emergent phenomena, to which the text belongs. Some of these difficulties were leveled by including a communicative approach in the linguist’s methodological baggage. At the same time, a significant layer of factors influencing on the meaning generation of the text remained outside the scope of the research focus. As a result, the linguocognitive approach to text analysis was formed in linguistics. This made it possible to include not only linguistic structures, but also the widest range of mental structures (concepts, frames and slots, prototypes, categories, conceptual oppositions, gestalts, mental spaces and models, conceptual metaphors, precedent phenomena, semantic networks) and cognitive operations (conceptualization, categorization, inference, causal attribution, conceptual projections, blending) in the analysis. Thus, the linguocognitive approach to text analysis increases the heuristics of scientific research due to it is aimed at studying of semantic processes as mental processes.

XAI Driven Intelligent IoMT Secure Data Management Framework.

The Internet of Medical Things (IoMT) has transformed traditional healthcare systems by enabling real-time monitoring, remote diagnostics, and data-driven treatment. However, security and privacy remain significant concerns for IoMT adoption due to the sensitive nature of medical data. Therefore, we propose an integrated framework leveraging blockchain and explainable artificial intelligence (XAI) to enable secure, intelligent, and transparent management of IoMT data. First, the traceability and tamper-proof of blockchain are used to realize the secure transaction of IoMT data, transforming the secure transaction of IoMT data into a two-stage Stackelberg game. The dual-chain architecture is used to ensure the security and privacy protection of the transaction. The main-chain manages regular IoMT data transactions, while the side-chain deals with data trading activities aimed at resale. Simultaneously, the perceptual hash technology is used to realize data rights confirmation, which maximally protects the rights and interests of each participant in the transaction. Subsequently, medical time-series data is modeled using bidirectional simple recurrent units to detect anomalies and cyberthreats accurately while overcoming vanishing gradients. Lastly, an adversarial sample generation method based on local interpretable model-agnostic explanations is provided to evaluate, secure, and improve the anomaly detection model, as well as to make it more explainable and resilient to possible adversarial attacks. Simulation results are provided to illustrate the high performance of the integrated secure data management framework leveraging blockchain and XAI, compared with the benchmarks.

Effect of lepidolite on melting, viscosity and structure of CaO–SiO2 based melt

It will be an economic, environmental-friendly and energy-saving way to utilize lepidolite as a substitution of industrial grade lithium carbonate for preparation of commercial mold flux. Therefore, the melting behavior, viscosity and melt structure of mold fluxes with different lepidolite content were investigated in this study. The results show that the initial melting temperature of the fluxes increases from 1278.4 to 1301.2 K, meanwhile the complete melting temperature increases from 1622.0 to 1674.4 K with the addition of lepidolite from 15.10 to 37.80 wt%. The viscosity of mold fluxes at 1573 K increases from 0.12 to 0.44 Pa s, whereas the break temperature reduces from 1467.7 to 1386.9 K with the increase of lepidolite. The melt structure analyses suggests that the simple structural units, such as Q0, Q1, Q2 and [AlO4]5-- tetrahedral asymmetric stretching reduce; while the complex structural units, like Q3, Q4, [AlO4]5-- tetrahedral symmetric stretching and Al–O–Si bending increase with the addition of lepidolite. These changes suggest that the free oxygen transforms into bridging oxygen and non-bridging oxygen, and the structure of melt becomes more complex when lepidolite is added in the flux.

Use of IV Hydration Instead of Exchange Transfusion for Prophylactic Management of Pain Crisis in Homozygous (SS) Sickle Cell Disease Helps Maintain Hgb Levels and Prevents Further Escalation of Iron Overload

Introduction: Indications for exchange transfusion in the management of sickle cell disease and its complications are over time becoming limited. Currently accepted indications include acute chest syndrome and cerebrovascular accidents only. However, there is often consideration of using exchange transfusions for management of sickle cell pain crisis episodes resistant to opioid-based pain management. This is, however, of questionable efficacy due to concerns of iron overload as well as alloimmunization. The excessive utilization of blood products also presents a significant challenge. Therefore, it is important to explore alternatives to exchange transfusion in the management of pain crisis in sickle cell disease. Method: This study aimed at investigating the effects of transitioning patients with homozygous SS disease from routine exchange transfusions to IV hydration protocols. The main objective was to examine the changes in Hgb levels and the status of iron overload in these patients. A cohort of 16 patients with a Ferritin level above 1000 ng/ml, who were already receiving regular exchange transfusions, were included in the study. Their Hgb levels and Ferritin levels were measured periodically. This group was then given IV hydration twice a week, regardless of whether they were experiencing pain issues. We then compared the Hgb and Ferritin levels during a 6-month period of active exchange transfusions and 6-month period of being on IV hydration protocols. Both periods were a year apart, allowing for adequate homeostatic changes to take place. Additionally, we compared the number of simple transfusions during both these periods. Result: The mean ferritin level in patients getting exchange transfusions was 6097 ng/mL with the mean Hgb level maintained at 7.48 g/dL. During the initial study period, there were 14 exchange transfusion sessions involving 96 units of packed red blood cells (PRBCs). Additionally, 8 units of simple transfusion units were administered during the same period. Interestingly, as this cohort transitioned away from exchange transfusions, the number of simple transfusions increased to 30. Only one exchange transfusion occurred during the second 6-month observation period. During this time, ferritin level stopped increasing, and the mean was measured at 6076 ng/ml. The Hgb levels did show a slight decrease, with the mean being 6.90 g/dL, but the difference was not statistically significant. Conclusion: The findings of this study suggest that the use of IV hydration protocol is effective in managing iron overload issues and maintaining an adequate Hgb level in patients who were previously undergoing routine exchange transfusions to prevent or manage pain crisis episodes. The results indicate that IV hydration should be initiated when ferritin levels increase beyond 1000 ng/ml, rather than waiting for more advanced stages. Moreover, the study shows that even when IV hydration is started at a later stage of iron overload, it still appears to limit further iron accumulation, as evidenced by the stabilization of ferritin levels. Overall, the use of IV hydration as an alternative to routine exchange transfusions holds promise in managing pain crisis and iron overload in sickle cell disease.