Coconut Coir Fiber Research Articles

Sound Absorption Characteristics of Composite Panel Made from Coconut Coir and Oil Palm Empty Fruit Bunches Fibre with Polyester

The development of pure natural fibres as sound absorptive material remains overlooked due to their lack of mechanical and moist properties, low durability, and vulnerability to be damaged by the environment. Certain fibre treatments are needed to improve such disadvantages. This paper investigates sound absorption characteristics of coconut fibre (coir) and oil palm fibre made from empty fruit bunches (OPEFB) fibre bonded by polyester that can protect them from the ambient environment in order to increase their durability. Two types of fibre-polyester composites have been tested. The first is the fibre-polyester composite (FPC) type, which is totally coated with polyester as the composite matrix. Another type is the fibre-polyester bonded composite (FPBC), in which the polyester is brushed into slice by a slice of the fibre layer in order to coat and bond the fibre, although porous among the fibre remains possible. A two-channel impedance tube is used in the measurement within 200 Hz to 3000 Hz of the frequency range. It is found that FPBC type panel has almost similar sound absorption characteristics to its purely natural fibre as it is able to maintain the panel porosity. The coconut coir fibre panel and its composite have a maximum absorption coefficient of almost 100% within the frequency range 1500-2000 Hz, considerably better than the OPEFB fibre, with only about 80% of the absorption coefficient. If the FPC layer exists, the sound absorption is reduced, and the frequency peaks are also shifted. Additions of the FPC panel layer thickness produced lower sound absorptions and shifted the peaks to the lower frequency range. The FPBC panel type is viable to protect the fibre from the environment without changing its sound absorption characteristics.

EXPERIMENTAL STUDY OF ACOUSTICAL INSULATION OF CEMENT-BASED BOARD PREPARED WITH WASTE COCONUT COIR AND OIL PALM FIBERS

ABSTRACT Among the major challenges facing the modern era of technological and industrial advancements are pollution and exponentially growing energy consumption. Pollution continues to be a menace affecting different aspects of life such as health, productivity, and comfort. This paper focuses on the elimination or reduction of sound pollution in buildings using cement-based boards made from pretreated coconut coir and oil palm fibers obtained from agricultural residues. The study includes an account of the preparation of fiber cement boards made from Portland cement Type 1, limestone powder, water, sand, and pretreated coconut coir and oil palm fibers at 5, 10, 15, and 20% by weight of powder materials, respectively, and a high-range water reducer in order to make sure that the natural materials would be spread in an even way throughout the specimens. Sound insulation tests were performed as key indicators of the performance of the fiber cement boards. It was found that an increase in the proportion of natural materials resulted in fiber cement boards with decreased density, compressive strength, and flexural strength. Furthermore, in relation to both physical and mechanical performance, the boards incorporating coconut fibers were superior to those incorporating oil palm fibers. With an increased proportion of natural fibers, sound insulation performance tended to improve. The boards prepared with coconut coir and oil palm fibers in this study yielded acceptable physical and mechanical properties and showed promise in relation to providing insulative protection against sound.

Competitive sorption of Cd, Cr, Cu, Ni, Pb and Zn from stormwater runoff by five low-cost sorbents; Effects of co-contaminants, humic acid, salinity and pH

For a comprehensive estimation of metals removal by sorbents in stormwater systems, it is essential to evaluate the impacts of co-contaminants. However, most studies consider only metals (single or multiple), which may overestimate performance. This study employed a batch method to investigate the performance of five low-cost sorbents – coconut coir fiber (CCF), blast furnace slag (BFS), waste tire crumb rubber (WTCR), biochar (BC), and iron coated biochar (FeBC) – for simultaneous removal of Cd, Cr, Cu, Ni, Pb and Zn from simulated stormwater (SSW) containing other contaminants (nutrients and polycyclic aromatic hydrocarbons). BFS and CCF demonstrated the highest sorption capacity of all metals (> 95% removal) in all systems (single and multi-contaminant). However, the presence of other contaminants in solution reduced metals removal for other sorbents, as follows (highest to lowest removal): single-metal > multi-metal > multi-contaminant solutions, and removal efficiency ranking among metals was generally Cr~Cu~Pb > Ni > Cd > Zn. Humic acid (HA) negatively affected the metal sorption, likely due to the formation of soluble HA-metal complexes; NaCl concentration did not impact removal, but alkaline pH improved removal. These findings indicate that sorbents need to be tested under realistic stormwater solution chemistry including co-contaminants to appropriately characterize performance prior to implementation.

The Self-Adhesive Carbon Powder Based on Coconut Coir Fiber as Supercapacitor Application

Activated carbon powder is a popular material used as an electrode material for large scale applications, especially supercapacitors because of its excellent physical and electrochemical properties. Self-adhesive carbon powder based on coconut coir was prepared via single-step pyrolysis and chemical activation with NaOH solution. A single-step pyrolysis was performed, including carbonization and physical activation in the N2/CO2 atmosphere. The physical temperature of 750 °C, 800 °C, 850 °C and 900 °C is the major focus to evaluate the behavior of self-adhesive activated carbon. The density and the microcrystalline characteristics of the electrodes are influenced by the physical activation temperature. The density feature was evaluated based on the approach of self-adhesive carbon reduction dimensions such as mass, diameter, and thickness. Microcrystalline behavior was performed by using X-ray diffraction method, and it has shown the good amorphous properties of the activated carbon. The self-adhesive activated carbon electrodes were characterized and evaluated in symmetrical supercapacitor cells. The electrochemical characterization of the carbon electrodes using cyclic voltammetry method found that the high specific capacitance of 96 F.g-1 in 1 M H2SO4 electrolyte at a low scan rate of 1 mV.s-1 with energy specific and power specific of 13.33 Wh.kg-1 and 48.03 W.kg-1, respectively.

The properties of cement boards reinforced with coconut coir fiber (Cocos nucifera) as building materials

Cement board is a composite made from lignocellulosic biomass or other materials and bonded with cement, that has advantages such as fire and termite resistance, and can use for some purposes. The cement board’s quality is affected by the biomass’s chemical components, especially hemicellulose and extractives. Treatment to reduce the content of these two compounds in fiber can improve the cement board quality. This study aimed to evaluate the cement board’s properties reinforced with coconut coir fiber (CCF). Pretreatment was performed on fibers by soaking in cold water for 24 hours and soaking in hot water for 1 hour to reduce the chemical compounds. The ratio between fiber-cement used varied to 1:2.75, 1:3.0, and 1:3.25 based on weight, while magnesium chloride (MgCl2) uses at 2.5% of cement weight as an accelerator. The mixtures hand-matt formed and cold-pressed for 24 hours, with a density of the board was 1.25 g/cm3. The panels kept for 28 days before tested. Physical and mechanical tests conducted according to ISO 8335-1987. Results showed that the cement board’s physical and mechanical properties made from CCF soaked in hot water at the ratio fiber to the cement of 1:3.25 is the best properties compared to others.

Effect of sonification in the alkalization process of coconut fiber to improve fiber strength

Coconut coir fiber is a natural fiber obtained from the coconut mesocarp, where in Indonesia, its utilization is still not optimal. The use of fiber as a functional material in the structural and filter requires optimal characteristics and related to lignocellulose content and modification of the fiber’s surface structure. One method of fiber modification that is mostly used is the alkalization process using NaOH solution, which aims to degrade lignin, which is rigid and brittle. This paper will discuss the effect of ultrasonic wave exposure (sonication) on alkalizing the fiber using a low concentration NaOH solution. The variation of the concentrations of NaOH solution used was 1, 3, 5, 7, and 9% with ultrasonic wave exposure for 30 minutes at temperatures of 50, 60, and 70°C. The mechanical strength of the fiber was characterized using a Thwing-Albert Testing Machine. The measurement results show that the maximum mechanical strength values obtained in the alkalization treatment for 30 minutes with a concentration of 5% NaOH solution at a temperature of 70°C is 295.13 MPa. This tensile strength increased by 68.33% compared to the untreated sample of 175.33 MPa. The strain obtained in this sample was 31.86% of the initial fiber length.

Effect of Epoxy Resin on CBR Improvement of Soft Clayey Subgrade Mixed with Coconut Coir Fibres

Road infrastructure is a key factor for the development of an economy. For construction of road pavements, good sub grade soil is a major feature which influences the design, construction and durability of the pavement. Pavements built on soft subgrade soils experience faster degradation due to the low strength and high compressibility of soft soil. Replacement of soft soil with good soil is not sustainable, since it is expensive and also impacts the environment. Stabilization of soft soil is a sustainable alternative which can be used to improve the properties of soft soil in-situ. The use of various additives can improve the properties of soft soils. In this study, the effect of using coconut coir in combination with polymeric resin on the improvement of properties of soft soil is studied. Coconut coir is a waste material which can be used as bio-fibers, but since they are decomposable, are used in combination with polymeric resin. The effect of random percentages of coconut coir along with polymeric resin on the compaction and penetration behaviour of soil is presented.

Effect of coconut fiber treatment with limestone water media on the fiber surface, wettability, and interface shear strength

The development of technology has increased the need for composite materials, where the technology of composite materials with natural fiber reinforcement is growing. The existence of natural fiber is very abundant, and it has not been fully utilized. Until now, the use of coconut fiber was still limited to the furniture and household handicraft industries. Coconut coir fiber has the potential as a raw material for composite materials. The lack of strength of the bonds is due to the hydrophobic fiber, and the fiber surface is less rough, and dirty. This study evaluates the coir surface characteristic of the fiber and its bounding with the polyester matrix after being treated by limestone water. The scanning electron microscope was used for observing fiber surfaces and surface matrix. The wettability test to observe fiber surface energy was performed. Interface shear strength to evaluate the bonds between fibers and matrix was determined. Coconut coir fibers were immersed in limestone water, with a 5 % percentage of limestone and time variations of 0, 4, 8, 12, 16, and 20 hours. The scanning microscope electron observations of fibers show that the fiber surface tends to be clean, rough, and grooved. The highest surface energy was obtained at 40.74 mN/m during the limestone water immersion for 8 hours. The highest value of the interface shear strength between the fiber and the matrix is 3.80 MPa during 8-hour immersion, 0, 4, 12, 16, and 20-hour immersion, respectively, 3.02, 3.09, 3.52, 3.47, and 4.40 MPa. The results showed that coir fiber with limestone water immersion for 8 hours had a clean, rough, and grooved surface so that the bond between the fiber and matrix was better. This research shows that limestone water can be used as a fiber treatment medium which was natural

Mechanical properties of composite board based on coconut coir and terminalia catappa fruit fibers with Polyvinyl Acetate (PVAc) Matrix

The synthesis of composite board made from a mixture of coconut coir and Terminalia catappa fruit fibers using Polyvinyl Acetate (PVAc) matrix has been successfully carried out. The synthesis aims to determine the effect of a mixture of coconut coir and Terminalia catappa fruit fibers with PVAc matrix on the mechanical properties of the composite board. The samples were made with variations in the composition of the volume fraction of coir fiber and Terminalia catappa fruit fibers, namely (30:70), (40:60), (50:50), (60:40), and (70:30)%. The ratio of the volume fraction of the mixture of natural fibers and the PVAc) matrix made was (70:30)%. The sample production begins with taking the coconut coir and Terminalia catappa fruit, drying and cutting, then mixing the coconut coir and Terminalia catappa fruit fibers with a PVAc matrix, printing the composite with printing tools and drying. The finished sample was then mechanically tested using the UTM tool AnD, model R3010. The results showed that the value of the maximum tensile stress and the modulus of elasticity increased with the increase in the concentration of coir fibers used. The value added in length and strain decreased with the decrease in the concentration of coco fiber used. Overall, the composite sample has met the SNI 03-02105-2006 criteria where the maximum tensile stress value ranges from 8.21 MPa to 18.81 MPa and the modulus of elasticity ranges from 829.71 MPa to 1620.67 MPa.

Simultaneous removal of multiple polycyclic aromatic hydrocarbons (PAHs) from urban stormwater using low-cost agricultural/industrial byproducts as sorbents

The potential of five low-cost and globally available sorbents, including three raw waste products – waste tire crumb rubber (WTCR), coconut coir fiber (CCF) and blast furnace slag (BFS) – and two modified materials – biochar (BC) and iron coated biochar (FeBC) – were evaluated for removing a mixture of polycyclic aromatic hydrocarbons (PAHs): pyrene (PYR), phenanthrene (PHE), acenaphthylene (ACY) and naphthalene (NAP) from simulated stormwater. The physicochemical characteristics of the sorbents were assessed by BET-N2 surface area, CHN elemental analysis, FTIR and scanning electron microscope (SEM-EDS). The experimental data were well described by both linear and Freundlich isotherm and pseudo-second order kinetic models. The adsorption rate was mainly controlled by the film diffusion mass transfer mechanism. The magnitude of PAHs partition coefficients (Kd) followed the order of BC > FeBC > WTCR > CCF ≫ BFS, ranging from 80 to 390,000 L/kg. The sorption Kd values were positively correlated with both aromaticity of sorbents and octanol-water partition coefficients (Kow) of PAHs. Solution ionic strength and pH did not have significant effects on the sorption of PAHs by all sorbents. In contrast, humic acid, as dissolved organic carbon, decreased sorption capacities of WTCR and CCF, and increased sorption efficiency of BFS, which was confirmed with field-collected real stormwater. The hydrophobic π–π interactions were the main mechanism for the sorption of PAHs by various sorbents. These findings are promising for future development of cost-effective sorption filters for removal of hydrophobic organic pollutants from urban stormwater runoff.

Waste composite of “JOS” coffee waste and gauze as alternative basic material for manufacturing craft products

The growth of coffee business in Indonesia has given rise to coffee shops in big cities, in Yogyakarta and its surroundings (2017) reaching 1,200. This number is higher than Semarang 700 and Solo only 400 shops. Yogyakarta as a student city is famous for its “jos” coffee, which is coffee infused with burning charcoal so that the sound of “jos” can rise. This city has many students, artists and younger generation who enjoy “jos” coffee. The “jos” coffee waste produced, one of which is in Pak Agus’ shop, is 4-6 kg/night. The aim of this research is to use “jos” coffee grounds waste as a basic material for making composites. The research method was carried out through experiments in the laboratory by making a composite waste of coffee grounds mixed with water, gauze fiber, coconut coir fiber, alginate, glycerol and gelatin. Composite composition consisted of “jos” coffee grounds from 10, 20 and 30 grams, 120 ml water, gauze, coconut fiber, 3 grams of alginate, 2 drops of glycerol, gelatin from 2,3,4, and 5 grams. The ingredients are cooked for 5 minutes, printed and then left for 24 hours. he resulting composites were tested for tensile, tear test, flexibility tested and observed for surface texture Composites with coconut coir fibers have poor surface texture and are easily fractured so that the mechanical properties of what is tested are composites reinforced with gauze fibers. The mechanical properties of the best composites were reinforced with gauze with a composition of 20 grams of coffee and 4 grams of gelatin, the tensile strength was 15.58 kg/mm2 and the tear resistance was 11.51 kg. From the observation that the composite has a smooth surface texture and can be bent up to 1800, so that it can be formed as an alternative material for making handicraft products.

Effect of Sodium Hydroxide (NaOH) Treatment on Coconut Coir Fibre and its Effectiveness on Enhancing Sound Absorption Properties

Natural fibre has been conventionally and widely utilised as a sound absorber in order to replace the traditional synthetic absorber materials. In this study, coir fibre (CF) was prepared as an acoustic absorber and subjected to an additional surface treatment by using sodium hydroxide (NaOH) at various concentrations ranging from 1% to 8%. This was geared towards analysing the effect of alkalisation on the fibre morphology, diameter, and changes occurring in the CF functional groups, thus resulting in enhanced sound absorption properties. To this end, the fibre surface was analysed using a scanning electron microscopy (SEM) to study the surface morphology of treated and untreated CF materials, whereas the implementation of Fourier-transform infrared (FTIR) allowed an analysis of CF characterisation. The absorber sample was fabricated at a constant thickness of 45mm and a density of 0.4g/cm3 density prior to testing for the sound absorption coefficient (SAC) by using an impedance tube. The morphology of CF revealed the treated fibres to be free of impurities including lignin and hemicellulose layer, which were removed from their surface. This finding was supported by the peak changes observed on the FTIR spectra. Furthermore, the fibre diameter was reduced as the concentrations of NaOH increased. The results conclusively indicated that treated CF at the concentrations of 7% and 8% NaOH gained the highest SAC values across the low and high-frequency ranges, yielding an α coefficient average of 0.9 and above.

Coconut coir fiber reinforced polypropylene composites: Investigation on fracture toughness and mechanical properties

Nowadays, research and development is focused on environmentally benign, sustainable materials to replace and reduce the dependence on existing petroleum-based products. In this framework, the growth of natural and man-made fiber reinforced composite materials is rising at a faster rate in the field of engineering and technology due to its promising characteristics. The current research work is focused on the development of coir fiber reinforced polypropylene composites (PPC) that is having widespread variety of applications and their characteristics are equivalent to present synthetic composites.The work is focused on the study of fracture toughness behavior of these composites and further characterization of mechanical properties. The fabrication of the specimen was carried out using Injection molding technique. Fracture toughness (Compact Tension) tests were done as per ASTM D-5045 standards. The Tensile, Impact, Flexural Strength, and Hardness tests were done to evaluate the mechanical characteristics. It is found that natural coconut coir fiber reinforced composites showed higher fracture toughness values and improved mechanical properties when compared to neat polypropylene.

Penggunaan Serat Kelapa untuk Pengolahan Limbah Cair Domestik

The oil and fat content in domestic wastewater is an element that can cause pollution of water bodies and inhibits the continued process in the Waste Water Treatment Plant. For this reason, efforts should be made to eliminate the womb in wastewater by filtration. In this study the filtration process uses a laboratory scale that is making a waste water solution from a mixture of water with various types of cooking spices that are fried using cooking oil and butter. The purpose of the study was to analyze the effectiveness of coconut fiber as a filter for waste oil (fat) in domestic wastewater. The research starts from the process of making coconut fiber and filtration tanks until it continues to the filtration treatment process. The results showed there were significant differences in oil (fat) levels in domestic wastewater between before and after filtration using coconut coir fiber media with a thickness of 20 cm, 40 cm and 60 cm, which obtained the value of p (p-value) ≤ value α (0 , 05), i.e. 0.019, 0.02 and 0.006. There is no significant difference in effectiveness between variations in thickness of coconut coir fibers as a filtration media against decreasing levels of oil (fat) in domestic wastewater, where a p-value of 0.073> α (0.05) is obtained. The effectiveness of each reduction is 89.24 (thickness 20 cm), 0.02 (thickness 40 cm) and 0.006 (thickness 60 cm). Coconut fiber is effective as a filtration media for treating domestic wastewater that contains oil (fat). It is recommended to conduct further research by increasing the residence time of wastewater in the filtration bath.

Mechanical and Acoustic properties of Bagasse – Coconut Coir based Hybrid Reinforced Composites

ABSTRACT In this paper, a hybrid composite is developed from natural fibers of bagasse and coconut coir. The mechanical and acoustic properties of the hybrid composites are investigated. While preparing the hybrid composites, the polyester resin is used as a matrix. Treated and untreated specimens were prepared by varying the weight percentage of bagasse and coconut coir fibers and resin. Various mechanical tests including tensile test, hardness test, flexural test, impact test and impedance tests were carried out as per ASTM standards. Experimental results on comparison reveal that the developed hybrid composite has a better sound absorption coefficient values and mechanical properties. Hence, the proposed hybrid composite could be used in Industries.

The effect of post-curing temperature on mechanical properties of coconut coir fiber reinforced polyester composite

This study used post-curing training as a method of strengthening. The smoking process was a process carried out in the form of heating the specimen at a certain temperature to improve the properties possessed by the composite. The purpose of this study was to study the effect of post-curing temperature on the impact strength of coconut coir fiber composites with temperature variations of 600ºC, 700ºC, 800ºC, 900ºC, 1000ºC. Specimens were prepared using a mixing method for mixing ingredients and a hand lay-up where in the composite volume fraction is prepared according to each specimen, which is 70% polyester and 30% coconut coir fiber. Each specimen is heated for 60 minutes in a conventional oven. Average impact strength and impact energy per unit area increases with the increase in post-curing temperature due to the fact that the movement of composites as well as the reduction of holes in the composites and adhesion to one another (suturing) can improve mechanical testing. The highest strength values obtained in the specimen with an increase in T = 100°C, ie 18,509 J for the average impact energy and 0,1434 J/mm2 for impact energy per unit area average.

Improvement of erosion-resistance of bio-bricks through fiber and multiple MICP treatments

Bio-bricks through MICP exhibits brittle properties and low water resistance. The goal of this study was to use fiber reinforcement and multiple MICP treatment to enhance the resistance of bio-bricks against accelerated water erosion. The reinforcing effects of synthetic fibers, coconut coir fibers, and multiple MICP treatment on properties of MICP-treated bio-bricks were investigated. Experimental results showed a significant improvement in the performance of bio-bricks could be achieved through fiber reinforcement and multiple MICP treatment. The flexure strength and strain of bio-bricks reinforced by 0.3% synthetic fibers increased from 1185 kPa to 1210 kPa, and 1.0% to 2.3%, respectively. The optimum coconut coir fiber content was around 0.6%-0.9%. Multiple MICP treatment method enhanced the resistance of bio-bricks against accelerated erosion significantly.

Effect of Polyurethane Resin Addition on Acoustic Performance of Natural Coconut Coir Fiber

ABSTRACT During the last few years remarkable efforts were taken for the development of natural sound-absorbing material. Recent advances in acoustic materials lead to a variety of natural sound-absorbing materials like jute, arenga pinnata, hemp, corn husk, to name a few. This article speaks for the sound absorption characteristics of coconut coir fibers with polyurethane resin. Results of this study revel sound-absorbing characteristics of coconut coir fiber and polyurethane resin with the help of impedance tube setup as per ISO 10534–2 and ASTM E1050-98 standards for the frequency range 100–5000 Hz. The acoustic performance of coconut coir fiber is measured by the addition of polyurethane resin with varying weight percentages such as 10%, 20%, 30%, and 40%. The absorption coefficient of 0.95 is achieved at high frequency 3200 Hz for 40 mm thickness with 70% fiber and 30% resin composition without air gap which is comparable with many synthetic materials. Same sample exhibit better result in comparison with another sample for low and medium frequency region showing a sound absorption coefficient of 0.4 (100–500 Hz) and 0.81 (500–1900 Hz). Finally, alongside the effect of the air gap of 0 mm, 10 mm, 15 mm, 20 mm, and 30 mm on sound absorption coefficient were measured.

An experimental and theoretical investigation of coconut coir material for sound absorption characteristics

Abstract This is comprehensive study on sound absorption performance of coconut coir fiber using experimental and theoretical approaches. Samples of coconut coir fiber with different thickness and densities were prepared to get their effect on sound absorption coefficient. Measurement of sound absorption coefficient was done by using impedance tube set up based on ISO 10534-2 and ASTM E1050-98 standards. Delany- Bazley model was used to find effect of thickness and density. In this paper the result sound absorption coefficient of theoretical and experimental study presented and compared. The result of Delany- Bazley model shows promising results compared with experimental results up to 2700–2900 Hz, further deviation in results were observed. Sound absorption coefficient of 0.84 (2900 Hz) for 35 mm thick sample with density 220 Kg/m3 was recorded. Further Sound Transmission Loss (STL) for 21 mm, 28 mm, 35 mm thickness samples with 220 Kg/m3 were measured using transfer function method of impedance tube. It was established that coconut coir fiber samples effectively dissipitate the sound energy giving fair sound absorption properties.

Finite element analysis for predicting the vibration characteristics of natural fiber reinforced epoxy composites

Modal analysis is a tool to predict the vibration characteristics such as natural frequencies, mode shapes and viscous damping coefficients of the structures. These characteristics play an important role in engineering design and analysis. In this paper, the prediction of vibration characteristics or modal-modal of cantilever beam made of neat epoxy and various natural fiber composites carried out by using finite element analysis software ANSYS 20.0. In this study, the natural fibers such as jute, banana, coconut coir, hemp and kenaf fibers are used as reinforcement in the epoxy matrix. The size of beam is 160 mm × 20 mm × 3 mm. The volume fraction of fiber is 33.33% taken for all natural fiber composite materials. The natural frequencies, damping factor and frequency response function bode plot are obtained with the help of ANSYS software. The damping factor is found out using half power bandwidth method from frequency response function bode plot. The natural frequency and damping factors of different natural fiber composites are compared with epoxy material. It is found from this analytical study that the damping factor values for each natural fiber composite material have higher values corresponding to each mode than that of epoxy material. Hence, it is concluded that the natural fiber composites have better damping properties than epoxy material. Hemp and kenaf fiber composite materials have similar values of natural frequencies for lower modes (1st mode and 2nd mode) and at higher modes (5th mode and 6th mode) respectively.