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This paper investigates the production of hydrogen (H2) and methane (CH4) from palm oil mill effluent (POME) using an integrated approach of thermophilic continuous stirred tank reactor (CSTR) and mesophilic microbial electrolysis cell (MECs). CSTR reactor was operated at pH 5.5, 80 rpm, 2 days HRT, 60 g COD L-1 d-1 organic loading rate (OLR) and 55 °C temperature with the given hydrogen yield of 205 ml H2 gCOD-1 along with acetic, butyric, propionic, and lactic acid as by-products. Continuous, single-chambered MECs fed with dark fermentation effluents were operated at an applied voltage of 0.5 V at 37 °C to obtain methane yield and production rate (MPR) of 290 ml CH4 gCOD-1 and 2700 ml CH4 L-1 at 8 days of hydraulic retention times (HRT). The overall process led to total energy recovery of 92.72% with 91% COD removal efficiency. Microbial community analysis reveals Thermoanerobacterium sp dominated in CSTR whereas exoelectrogens of Methanobacterium formicicum and Methanobacterium beijingense were found to be the chief dominant microbial species on anodic electrode of MECs.

The economy of an industrialized country is greatly dependent on fossil fuels. However, these non-renewable sources of energy are nearing the brink of extinction and which have caused serious adverse impacts on the environment. Hydrogen has emerged as a promising alternative and also has the highest calorific value. Bio-hythane is a hydrogen-methane blend can be produced from different organic substrates by two sequential anaerobic stages: a dark fermentation step followed by a second an anaerobic digestion step, for hydrogen and methane production, respectively. Bio-hythane is considered to be promising approach in sustainable energy sector. The advantages of two-stage technology include; high organic removal, high energy recovery and environment friendly. However, current efforts to recover bio-hythane energy from waste are still at bench scale level. The technical constraints in the fermentation must be removed for the indispensable bio-hythane recovery from waste. This short technical note highlights the two-stage fermentation and the technical barriers to be addressed for bio-hythane scale up from waste.

The utilisation of cellulosic fibre in removing organic and nutrients pollutants in polluted river is becoming an increasingly popular alternative cost-effective and sustainable option. However, the related empirical models are yet to be fully comprehensive to study the adsorption mechanisms of natural adsorbents. This paper discusses developed empirical model used to estimate the mass transfer of organic pollutants into two natural fibres – coconut fibres and oil palm fibres to filter pollutant molecules in water. An empirical model was developed to estimate the mass transfer of organic pollutants in water onto the fibres in a fabricated physical model. The mass transfer relations were derived based on the substrates loading rates and the predicted accumulation rates of substrates in fibres along with the percentage of outflows. Matching empirical results with experimental results showed that the modified model was able to accurately predict the mass transfer rate. The higher adsorption rate of CF (91.02% COD) depicted greater global mass transfer rate (1.3696 d−1) than OPF (82.35% COD) which only had 1.2768 d−1 of global mass transfer rate in 3% of COD outflow. The contribution of internal diffusion mechanism was significant due to the physical (porosity) and chemical (lignin and cellulosic content) characteristics of both CF and OPF. The study concluded that the performance of biological adsorption using CF and OPF is promising. 1. Introduction River has been the source of life since billions of years ago. Early human civilization had mainly flourished at riverbanks, such as Egypt’s Nile River, Indus River valley, and along major rivers in China. River forms a vital part of our ecosystem, providing food and shelter to many organisms, not to forget a mean of transportation for human [1]. In order to preserve its sustainability, it is important that river water bodies and riparian zones are maintained clean so that the delicate life balance is not disrupted. Ironically, as human civilization progresses by leaps and bounds throughout history, we are also stressing our river bodies through the tremendous amount of wastes generated. Many of these wastes are disposed irresponsibly into our river systems, overloading the rivers with excessive amount of nutrients that has resulted in harmful

The world is experiencing high rates of urbanisation and it has slowly become an alarming social process, especially in developing countries. This has demanded an urgent investigation on human thermal comfort, especially in tropical climates. In this study, a surrogate human sensor (SHS) was developed to establish a linkage between human skin surface and SHS with the surrounding environments. Black plastic corrugated cardboard was used in the SHS fabrication as its thermal conductivity was close to the thermal conductivity and emissivity of the human epidermal skin layer. The SHS was designed to correlate with human skin surface temperature and a regression model was developed. The regression equation was obtained for the human skin temperature prediction (Th) by using SHS. Statistical analysis of the ANOVA (F = 13,700; ρ

The heat generated from dark color asphalt, which is low in surface reflectance mainly contributes to the environmental problem called as urban heat island. Low reflectance at high energy wavelength of sunlight, such as visible light and infrared region will cause the pavement to have high surface temperature, due to high energy absorption from solar radiation. This paper presents the optimization result of cool pavement coating material based on selected tiles aggregate to achieve high near infrared region (NIR) reflectance. Three types of waste tiles were used in this study which are Full Body Porcelain (FBP), Monoporosa (MP) and Porcelain Glaze (PG). All the tiles were prepared in the form of aggregates. A linear model was formed as a function of mix tiles fraction and the analysis of ANOVA suggest that the linear term used for this model is significant. Diagnostics of the model was evaluated using box-cox plot, normal plot of residuals and optimized to predict the mix of the different type of tiles to produce the highest surface NIR reflectance value. The first solution suggests that 100% of MP tile can provide NIR reflectance of 0.53, whereas the second solution suggest that the combination of 50% FBP and 50% of MP tile aggregates could give NIR reflectance value of about 0.51. Experimental work on measuring surface temperature found that optimized samples, M1 and M2 with high NIR reflectance could significantly reduce surface temperature of asphalt pavement at range of 4.1 °C–9.6 °C. In conclusion, the results of optimization is reliable and this method able to provide significant information on optimizing mix of tiles material as to achieve high NIR reflectance value for coating materials of cool-pavement.

Hydrogen (H2) is often considered as the best option to store energy coming from renewable sources. Hydrogen production from lignocellulosic biomass via fermentation offers low cost and environmental friendly method in terms of energy balance and provides a sustainable pathway for utilization of huge amount of unused biomass. In this regard, special attention on potential of different lignocellulosic biomass is required. In this paper, the fermentative hydrogen production from three carbohydrates-rich biomass: water hyacinth, wheat straw and rice straw is comprehensively reviewed. In other point of view, usage of H2 has a 10% growth annually that will reach to 8–10% of total energy in 2025. Furthermore, research on recent trends of fermentative hydrogen production is crucial and vital. However, the majority of the published researches in the last decade confirmed that some challenges exists which are the process optimization, effecting parameters and commercialization aspects.

Malaysia is considered as one of the major palm oil producers in the world. Therefore, it is important to develop an environmentally friendly and economic method to treat palm oil mill effluent (POME). The main aim of this study was to investigate the potential of Lemna minor ( L. minor ) and Chlamydomonas incerta ( C. incerta ) with catalog number (KR349061) for the bioremediation of POME in order to achieve higher water quality standard and further produce organic fertilizer. In this study, three different experiments were conducted by using L. minor , followed by addition of C. incerta , and further combination of L. minor and C. incerta . The concentration of nitrate (NO 3 − ), ammoniacal nitrogen (NH 3 -N), phosphate (PO 4 -P), Electrical Conductivity (EC) and salinity in produced fertilizer were measured, and then they were compared with two current commercial fertilizers. Growth factors such as growth rates, average number of leaf and height of root of L. minor of plants were also determined. The results showed that the microalgae and macrophytes were capable of removing only 4.4% of chemical organic demand (COD) whereas the respective maximum removal rates for NO 3 − , NH 3 -N, and PO 4 -P were 12.5%, 11.3%, and 70.47%. Also, the average differences of NO 3 − , NH 3 -N, and PO 4 -P concentrations in produced fertilizer in comparison with two current commercial fertilizers were 95, 39.5, and 62.5 mg/g, respectively. The results of this study revealed that only L. minor was converted into fertilizer. This study elaborated that both L. minor and C. incerta are able to remove a part of organic pollutants and nutrients from POME.

Thermal performance are important parameter that represent the characteristic of cool pavement. The purpose of this paper is to present the findings on experimental result of thermal performance of the coating materials, which were developed from three types of waste tile aggregate, namely Full Body Porcelain (FBP), Monoporosa (MP) and Porcelain Glaze (PG). The samples were prepared based on the optimal design mix as proposed during optimization process based on surface temperature behavior of the samples. Experimental work was conducted in 24-h basis for continuously 14 days at actual tropical weather climate. The results showed that sample M1 with 100% of FBP provided the best result in terms of thermal performance, also the material was able to obtain highest surface temperature reduction up to 6.4 °C during peak period and solar reflectance of 0.49 at near infrared region. Statistical analysis shown that sample M4, 100% of PG tile aggregate, depicted a less desirable result due to its surface temperature reduction was not significant as compared with other investigated samples, which is only 4.32° during peak period. Overall result conclude that both material FBP and MP have a good potential to be used as cool pavement coating material based on its thermal and spectral performance. Thus, this study provides a useful information on the selection of tiles material that could be used as cool-pavement coatings, and contribute for a more potential measurement in mitigating urban heat island effects.

Fast industrialization has increased the demand for heavy metals, on the other hand, high-grade ore natural reserves are belittling. Therefore, alternative sources of heavy metals need to be investigated. Massive amounts of industrial wastes are being generated annually. The majority is sent to landfills or to incinerators, which eventually poses environmental challenges such as ecological contamination and health hazards to living beings. Such industrial wastes contain hazardous elements of various metals (Au, Ag, Ni, Mo, Co, Cu, Zn, and Cr), whose improper disposal leads to adverse effects to human being and the environment. As a result, methods for industrial waste management such as reuse, remanufacturing, and recycling have received much attention due to the fact that they improve cost effectiveness over time and enable the metal recovery businesses to thrive profitably. The present study provides a state of art review on the current technologies existing for the recovery of precious metals from industrial wastes streams to analyse the sustainability. Among the wastes, spent petroleum catalysts, medical waste, electronic scraps, battery wastes, metal finishing industry waste, and fly ash are some of the largest industrially-generated wastes. Various metal recovery processes involve physical, chemical, and thermal characteristics of waste streams and target metals for separation and extraction. The current challenges of pyrometallurgy, modification on the hydrometallurgy, physical and chemical methods and other advanced technologies are presented in this review. The hydrometallurgical method, which involves dissolving and leaching, is a proven and successful process for recovering metals from various raw materials. Several other recovery methods have been proposed and are currently being implemented; the problem is that most of them are only successful in retrieving certain metals based on specific properties of industrial waste. The recovered metal solutions are further concentrated and purified using adsorption, cementation, chemical precipitation, ion exchange, membrane filtration and ion flotation techniques, which can also be applied to other liquid waste streams. The recovery method only makes sense if the recovery cost is much less than the value of the precious metal. The limitations placed on waste disposal and stringent environmental legislation require environmental-friendly metal recovery technologies. This review paper provides critical information that enables researchers to identify a proper method for metal recovery from different industrial wastes, and also it benefits researchers and stakeholders in determining research directions and making waste management-related decisions.

River pollution from the agriculture industry has become an important cause of unscheduled water disruptions in Malaysia. Thus, rigorous control and treatment of high strength wastewater prior to discharge into the river are needed. This study aims at evaluating the performance of a pilot membrane bioreactor (MBR) for the treatment of palm oil mill effluent (POME). POME was subjected to MBR operating in an aerobic environment for 40 days, followed by 10 days without aeration and water pumping to simulate failure event, and finally resumed to operational condition. Higher proportions of protein (-PN) compared to polysaccharides (-PS) were present in both the mixed liquor and biofilm, indicating that protein was the main constituent of extracellular polymeric substances (EPS). Biological samples from the mixed liquor and biofilm on the membrane surfaces were collected on day 25, 50 and 75 to investigate taxonomic distribution of microbial community. High throughput sequencing of the 16S rRNA gene was used to investigate the composition of microbial communities in the MBR. Microbial groups such as the phyla Proteobacteria (19–23%), OD1 (11–15%), Chloroflexi (11–13%) were the dominant members in biofilm under operational condition while OD1 (20%), Proteobacteria (18%) and Planctomycetes (16%) were found to be dominant in biofilm under static and non-operational conditions. The taxonomic profile of the microbial community on day 75 is more similar to that of day 25, compared to day 50, suggesting the capability of the microbial communities to revert to the operational state despite a period of downtime.

Environmental pollution specifically water pollution is alarming both in the developed and developing countries. Heavy metal contamination of water resources is a critical issue which adversely affects humans, plants and animals. Phytoremediation is a cost-effective remediation technology which able to treat heavy metal polluted sites. This environmental friendly method has been successfully implemented in constructed wetland (CWs) which is able to restore the aquatic biosystem naturally. Nowadays, many aquatic plant species are being investigated to determine their potential and effectiveness for phytoremediation application, especially high growth rate plants i.e. macrophytes. Based on the findings, phytofiltration (rhizofiltration) is the sole method which defined as heavy metals removal from water by aquatic plants. Due to specific morphology and higher growth rate, free-floating plants were more efficient to uptake heavy metals in comparison with submerged and emergent plants. In this review, the potential of wide range of aquatic plant species with main focus on four well known species (hyper-accumulators): Pistia stratiotes, Eicchornia spp., Lemna spp. and Salvinia spp. was investigated. Moreover, we discussed about the history, methods and future prospects in phytoremediation of heavy metals by aquatic plants comprehensively.

In the present study we investigated the fuel properties of bio-briquettes made from a combination of water hyacinth and empty fruit bunch fiber (palm oil mill residue). Water hyacinth (WH) was mixed with empty fruit bunch (EFB) fibers in a ratio of 25, 50, 75, 90, and 100% by weight and cassava starch added as binder. The experimental results showed that the addition of WH had a little effect (p < 0.05) on the physical and combustion properties of the briquettes. The proximate analysis showed that the moisture content, ash content and fixed carbon content were increased with the increase in WH amount from 25 to 100%, while the volatile matter content and calorific value decreased. Combustion test showed that the increase in the WH percentage in bio-briquette resulted in the decreased of O2 and CO level, whereas, that of CO2 and NO, NO2 and SO2 were increased. Therefore, the results conclude that the WH: EFB biomass bio-briquette could be a great potential as an alternative source to conventional coal to minimize the emission of greenhouse gases.

Considering the era of industrialization and increasing growth of interest in the green bioconversion of biomass into efficient value-added products, this review discusses the hydrogen (H2) production using the hyperthermophilic bacteria as a promising strategy for the agriculture and industrial purposes towards the generation of clean energy. Production of microbial enzymes through hyperthermophiles is beneficial as they are more resistant and stable in a controlled closed production system. Among hyperthermophile bacteria, thermotogales include species with the ability to grow optimally at temperatures ≥80 °C and to produce high yields of H2. Thermostable enzymes are able to degrade different biomass materials and produce H2, it attained much attention for the scholars and have been used at the industrial scale. The biohydrogen pathways of thermotogales and the obstacles during the fermentation process need to be deeply examined. Therefore, this work critically reviewed the hydrogen production of Thermotoga species and their application to different biomass. Moreover, a critical discussion on the hyperthermophilic hydrogenic bacteria is provided followed by its genetic modifications and challenges associated to realize its future sustainability. In addition, this paper discusses the challenges of improving hydrogen production. Finally, it was concluded that using thermostable enzymes produced by extremophilic bacteria such as T. maritima will lead to green development through producing high hydrogen yields.

Effluent from the aquaculture industry discharged into water bodies and it impacts the environment severely. The shrimp industry is one of the developing aquacultures that releases a high amount of organic matters in the form of wastewater. As an effort to reduce the environmental impact, an integrated system with shrimp and macroalgae researched abundantly as the macroalgae are naturally capable of removing nutrient from wastewater. As a bioremediation potential, this study investigates the nutrient uptake and macroalgal growth performance in short term (21 days) using an outdoor recirculating water system stocked with two local macroalgae species Gracilaria edulis and Gracilaria changii as biofilter. The stocking density of 3 kg/m 2 with the flow rate of the water system set to 200 L/hr during the operation. The temperature, pH, dissolved oxygen (DO) and salinity was measured daily throughout the experimental period. Water temperature in all tanks were almost constant and ranged between 28.5 °C to 29.1 °C. The higher mean of pH of around 8.26 ± 0.15 and 8.28 ± 0.05 was observed in tanks with G. edulis and G. changii respectively. In the control tanks, mean pH was 7.87 ± 0.09. The mean concentrations of dissolved oxygen in G. edulis, G. changii and control tanks were 6.89 ± 0.05 mg/L, 6.84 ± 0.06 mg/L, and 6.10 ± 0.03 mg/L respectively. The mean growth rates of Gracilaria edulis and Gracilaria changii were found to be 4.3% day − 1 , 4.1% day−1 with carbon to nitrogen (C:N) ratio of 8.3 to 8.5 respectively. The removal rate of ammonium and nitrate by the two species were found to be 72.5%, 71.0%, and 58.8%, 56.8% respectively. The macroalgal biofilter is found to be an ecologically sustainable that has improved the shrimp water quality to an acceptable level that in turn ultimately enhanced shrimp and macroalgae productivity.

Malaysia is considered as a major palm oil producer in the world. Therefore, it is vital to utilize an environmentally friendly and inexpensive method to treat palm oil mill effluent (POME) in Malaysia. Nowadays, the use of microalgae to remove pollutants from POME has gained a lot of attention. The main objective of this research was to investigate the effect of POME as a nutrient on the microalgae growth and analyze the removal rate of pollution. In this study, a pure culture Chlamydomonas incerta was aseptically transferred to an Erlenmeyer flask containing POME. The effect of POME as a high nutritional substrate, different cultivation scales, carbon total nitrogen (C:TN) ratio, and the lipid productivity of microalgae C. incerta were assessed. C. incerta was grown at room temperature under continuous illumination with the intensity of ± 15 (μmol/m2/s) for 28 days, followed by the measurement of chemical oxygen demand (COD) reduction at different substrate concentrations. The results of this study demonstrated that organic carbon was removed by C. incerta for the ratio of 100:7, 100:13, and 100:31 respectively within the second day of cultivation. Fast growth of microalgae was observed in organic and inorganic substrates for adoption within the second day of experiment. The optimum achievement rate of nutrient removal with C. incerta was about 67.35% of COD for 250 mg/L of POME concentrations in 28 days. The significance of this study is regarding the introduction of a new microalgae strain with a high ability to remove nutrients from POME, which can contribute to the effort in finding an efficient and economic technology for improving our environment.

Water hyacinth was introduced as an ornamental crop in many countries more than a century ago, due to its attractive appearance and aesthetical value in the environment. Unfortunately, the flowers developed into invasive species due to their adaptability for a wide range of fresh water ecosystems and their interference with human activities. In the 21st century, they were considered as an alternative to fossil fuels, as many researchers found them capable of converting their content into fuel energy at less cost and recognized as an eco-friendly product. As water hyacinth is among the group of fastest growing plants, its biomass has the potential to become a potential renewable energy source and replace conventional fossil fuels, perhaps during the next decade. This is an essential mission to overcome the depletion of energy sources and also to fulfill the increasing demand of world energy. Instead of fuel energy, the dried biomass can also be fabricated as briquettes, which is suitable as co-firing agent in coal power plant. Thus, in future compacted biomass residues produced in the form of briquettes may decrease the dependence of coal to provide more energy The other application of water hyacinth into a co-compost material such as soil amendment to the sandy soil, can improve hydro-physical, chemical parameters of soil and will supply the growing crops with several nutrients. Water hyacinth has also drawn attention due to its bioremediation ability, capable of removing pollutants from domestic and industrial waste water effluents. Thus, the issue of water hyacinth should be evaluated from energy, engineering as well as environmental perspectives. In this review, the potential uses of water hyacinth are being classified and discussed.

High concentration of phosphate (PO3- 4) released from wastewater treatment plant effluent (WWTPE) can negatively impact aquatic ecosystems and human health. Even though adsorption techniques have been widely used to remove PO3- 4 from waters, an empirical model used to describe the adsorption of PO3- 4 onto a porous material is still not yet fully understood. In this study, the empirical models of bed depth service time (BDST), Thomas and mass transfer factor (MTF) are used to scrutinize the adsorption behaviors of PO3- 4 removal from a domestic WWTPE onto the granular laterites applied to a hybrid plug flow column reactor. Despite the applications of Thomas and MTF model are verified suitable for use with general-purpose data models, the BDST is only applicable to model the data of monitoring PO3- 4 after seeing a more than 50% outflow. The dynamic adsorption capacity, adsorption rate constants and equilibrium solute uptake are determined. The resistance of mass transfer for the adsorption of PO3- 4 onto granular laterites in aqueous solution before breakthrough occurred to continue until the outflow reaches at certain percentage is only dependent on porous diffusion. The application of experimentally verified adsorption data binding with three different models can make significant contributions to improving environmental quality.

The study explores on upstream and downstream process in Microcystis aeruginosa for biodiesel production. The alga was isolated from temple tank, acclimatized and successfully mass cultivated in open raceway pond at semi-continuous mode. A two step combined process was designed and harvested 99.3% of biomass, the daily dry biomass productivity was recorded up to 28gm(-2)day(-1). The lipid extraction was optimized and achieved 21.3%; physicochemical properties were characterized and found 11.7% of FFA, iodine value 72% and 99.2% of ester content. The lipid was transesterified by a two step simultaneous process and produced 90.1% of biodiesel; the calorific value of the biodiesel was 38.8MJ/kg. Further, the physicochemical properties of biodiesel was characterized and found to be within the limits of American ASTM D6751. Based on the areal and volumetric biomass productivity estimation, M. aeruginosa can yield 84.1 tons of dry biomass ha(-1)year(-1).

The present study examined the synergistic effect of alum-modified cassava peel starch as dual coagulants in removing total suspended solids and Escherichia coli in dam water. The optimisation study was carried out to evaluate the effects of pH, coagulant dosage, and settling time on the flocculation performance of the coagulants. Alum as sole coagulant and combination of alum and native cassava peel starch were also studied for comparison purpose. Characterisations of the coagulants using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy studies confirmed the successful modification of cassava peel starch. Characterization studies revealed changes in surface morphology, elemental distribution after the modification. Pores, rough surfaces and several new element including Cl and Ca were observed on the surface of the modified starch. The presence of important active groups such as citral that responsible for antimicrobial and flocculation function was also reflected in the modified starch coagulant. The optimisation study indicated distinct performance of alum-modified cassava peel starch compared to alum alone and alum-cassava peel starch in terms of both flocculation and antibacterial functionality. High removal of both TSS and E. coli was achieved with the treatment using the combination of alum-modified cassava peel starch with superior removal of 92.75% and 100%, respectively, within 10 min of settling time using the recommended working conditions of alum-modified cassava peel starch dosage of 7.5–50 mg/L at pH 7. Additionally, the characterisation of flocs indicated that the employment of alum as sole coagulant and alum combined with the modified starch possessed distinctive features. Scanning electron micrograph showed that the flocs formed using alum-modified cassava peel starch was highly compacted clusters with appearance of E.coli cells embedded in the floc matrix, whereas for alum as the sole coagulant, the flocs were irregular-shaped and aggregated. Besides, the difference in peak occurrence from analysis reflected different mechanisms of floc formation using alum alone and alum-modified cassava peel starch. From the floc analysis study, charge neutralisation, bridging and sweep flocculation were the mechanisms that are expected to govern the coagulation and flocculation process.

The views of the public on solid waste bound to be generated in Johor Bahru Malaysia are presented and appraised. This is because of the massive development currently going on to transform the city to an international standing by the year 2025. For this reason, attempts to raise stakeholder awareness on the need to embrace on how best to manage the current problem with reduced impacts to the environment currently and in the future was attempted. Data were collected through contacts and questionnaire survey. Analytical hierarchy process (AHP) technique was used to structure and assess the views and judgments of stakeholders on the environmental impacts of solid waste disposal. SuperDecision software was used to generate and compute results of stakeholder's judgments. The assessment revealed that fauna and flora, habitat depletion and land use among the criteria are most critical environmental impacts. Landfilling, recycling, incineration and composting were evaluated in terms of the environmental impacts. The choice of incineration is perceived to improve environmental visibility, preserves fauna and flora as well as stream ecology, improves environmental air quality and optimizes land use. Similarly, recycling of waste, is perceived to preserves fauna and flora, stream ecology, habitat depletion, improves air quality as well as land use. Composting is perceived to be the best option in terms of preservation of stream ecology, habitat depletion and land use practice. Landfill generates less noise and vibration but found to be responsible for more than 50% of the environmental impacts created by solid waste in this area. Composting and recycling are mostly preferred to landfilling and incineration and the reason why this is so was provided. The study also identified challenges ahead and highlights that benefits attached to some vital disposal options (such as incineration) are yet to be fully implemented.