High Environmental Impact Research Articles

The Heteropolyacid-Catalyzed Conversion of Biomass Saccharides into High-Added-Value Products and Biofuels

The industrial processes used to produce paper and cellulose generate many lignocellulosic residues. These residues are usually burned to produce heat to supply the energy demands of other processes, increasing greenhouse gas emissions and resulting in a high environmental impact. Instead of burning these lignocellulosic residues, they can be converted into saccharides, which are feedstock for high-value products and biofuels. Keggin heteropolyacids are efficient catalysts for obtaining saccharides from cellulose and hemicellulose and converting them into bioproducts or biofuel. Furfural, 5-hydroxymethylfurfural, levulinic acid, and alkyl levulinates are important platform molecules obtained from saccharides and raw materials in the biorefinery processes used to produce fine chemicals and biofuels. This review discusses the significant progress achieved in the development of the processes based on heteropolyacid-catalyzed reactions to convert biomass and their residues into furfural, 5-hydroxymethylfurfural, levulinic acid, and alkyl levulinates in homogeneous and heterogeneous reaction conditions. The different modifications that can be performed to a Keggin HPA structure, such as the replacement of the central atom (P or Si) with B or Al, the doping of the heteropolyanion with metal cations, and a proton exchange with metal or organic cations, as well as their impact on the catalytic activity of HPAs, are detailed and discussed herein.

Optimization Strategies of Hybrid Lithium Titanate Oxide/Carbon Anodes for Lithium-Ion Batteries

Lithium-ion batteries, due to their high energy density, compact size, long lifetime, and low environmental impact, have achieved a dominant position in everyday life. These attributes have made them the preferred choice for powering portable devices such as laptops and smartphones, power tools, and electric vehicles. As technology advances rapidly, the demand for even more efficient energy storage devices continues to rise. In lithium-ion batteries, anodes play a crucial role, with lithium titanate oxide standing out as a highly promising material. This anode is favored for its exceptional cycle stability, safety features, and fast charging capabilities. The impressive cycle stability of lithium titanate oxide is largely due to its zero-strain nature, meaning it undergoes minimal volume changes during lithium-ion insertion and extraction. This stability enhances the anode’s durability, leading to longer battery life. In addition, the lithium titanate oxide anode operates at a voltage of approximately 1.55 V vs. Li+/Li, significantly reducing the risk of dendrite formation, a major safety concern that can cause short circuits and fires. The material’s spinel structure, with its large active surface area, further allows fast electron transfer and ion diffusion, facilitating fast charging. This review explores the characteristics of lithium titanate oxide, the various synthesis methods employed, and its integration with carbon materials to enhance cycle stability, coulombic efficiency, and safety. It also proposes strategies for optimizing lithium titanate oxide properties to create sustainable anodes with reduced environmental impact using eco-friendly routes.

Innovative Approaches in Water Decontamination: A Critical Analysis of Biomaterials, Nanocomposites, and Stimuli-Responsive Polymers for Effective Solutions

In recent years, smart materials have emerged as a groundbreaking innovation in the field of water filtration, offering sustainable, efficient, and environmentally friendly solutions to address the growing global water crisis. This review explores the latest advancements in the application of smart materials—including biomaterials, nanocomposites, and stimuli-responsive polymers—specifically for water treatment. It examines their effectiveness in detecting and removing various types of pollutants, including organic contaminants, heavy metals, and microbial infections, while adapting to dynamic environmental conditions such as fluctuations in temperature, pH, and pressure. The review highlights the remarkable versatility of these materials, emphasizing their multifunctionality, which allows them to address a wide range of water quality issues with high efficiency and low environmental impact. Moreover, it explores the potential of smart materials to overcome significant challenges in water purification, such as the need for real-time pollutant detection and targeted removal processes. The research also discusses the scalability and future development of these materials, considering their cost-effectiveness and potential for large-scale application. By aligning with the principles of sustainable development, smart materials represent a promising direction for ensuring global water security, offering both innovative solutions for current water pollution issues and long-term benefits for the environment and public health.

Eco-Control and Its Dual Impact on Environmental and Economic Performance

This study examines the dual impact of eco-control on both environmental and economic performance in the manufacturing sector. Drawing on data from 183 managers of manufacturing companies in Indonesia, this research employs Partial Least Squares Structural Equation Modelling (PLS-SEM) to analyse the relationships between eco-control, environmental performance, and economic performance. The findings reveal that eco-control significantly enhances environmental performance, which in turn positively influences economic outcomes. Additionally, eco-control has a direct positive effect on economic performance, suggesting that firms with robust eco-control mechanisms are more likely to achieve greater operational efficiency and financial success. The mediation analysis further confirms that environmental performance plays a crucial role in transmitting the positive effects of eco-control to economic performance. These results contribute to the growing body of literature on sustainability and corporate strategy by demonstrating the value of integrating eco-control systems to achieve both environmental and economic objectives. The study also highlights the importance of eco-control in aligning corporate sustainability initiatives with long-term profitability, particularly in sectors with high environmental impact. Limitations and directions for future research are discussed, including the need for broader studies across different industries and regions.

Unveiling The Impact of Green Accounting and Sustainability Disclosure On The Firm Value

This study examined the impact of green accounting and sustainability disclosure on firm value in the Indonesian palm oil industry. The objective was to empirically assess how environmental performance measured by PROPER and sustainability reports affects firm value. Using quantitative research methods, the study analyzed data from 124 palm oil company observations listed on the Indonesia Stock Exchange from 2018 to 2022. The research variables included firm value proxied by Tobin’s Q, green accounting proxied by PROPER scores, and sustainability disclosure indexed from the companies’ sustainability reports. The study also included profitability, firm size, and leverage as control variables. The results indicated that green accounting had a negative impact on firm value, suggesting that environmental compliance imposes short-term financial burdens on companies. However, sustainability disclosure did not significantly influence firm value, indicating that investors in the palm oil industry may prioritize short-term financial performance over long-term sustainability considerations. These findings contribute to the literature on corporate governance and sustainability, particularly in industries with high environmental impact, like palm oil.

Application of a decision tree approach to predict energy consumption in lightweight buildings under subtropical climate

PurposeLightweight building systems have emerged as alternatives to reduce the high environmental impact of conventional masonry. However, in subtropical climates, the low thermal inertia of lightweight envelopes negatively affects energy performance. The purpose of this paper is to investigate the thermophysical parameters that influence heating and cooling energy consumption in lightweight residential buildings under subtropical climates and develop a model to predict these parameters using statistical and machine learning tools.Design/methodology/approachA database was created with computer simulation data on the energy performance of 2048 building conditions generated by factorial combination of 10 parameters. Sensitivity analysis was performed to identify which parameters contribute most to energy performance indicators. Subsequently, decision trees were created using a classification and regression tree (CART) algorithm to visualize parameters and improve energy performance indicators, particularly cooling energy consumption.FindingsLow thermal transmittance and ground contact are interesting strategies for low thermal capacity buildings. Furthermore, the findings showed that relying only on the most influential properties does not ensure good energy performance; rather, it is the adequate combination of envelope properties that leads to good energy efficiency. The tree developed by CART can be used as a guide to assist designers and researchers in the initial selection of building envelopes, demonstrating the impact of each choice on electrical energy consumption for indoor climate control.Originality/valueBy adopting a global approach to assess the thermal performance of lightweight buildings, this study makes a significant contribution to synthesizing the results of a complex and time-consuming methodology into a guide for optimizing envelope design decisions and directing efforts and resources toward efficient strategies.

Enhancing food sustainability in the acute hospital setting - a nurse-led study of patient food.

Intensive global food production causes soil, water and air pollution, which has a negative impact on our health and future ability to produce sufficient nutritious food. Plant-based diets have the potential to reduce the environmental damage associated with the global food chain. The project sought to understand drivers of food waste and to improve food sustainability in a busy, tertiary referral hospital in England. Ward-level food waste was quantified. Qualitative data were collected using informal interviews with staff and additional data utilised the patient feedback survey. Ward-level food packaging waste and patient food choices were quantified using data on patient menu choices. The carbon footprint of patient food choices was calculated. Beef was the most popular menu choice, and was the main contributing factor to the high environmental impact of the hospital food chain. Increasing the visibility of vegetarian options on the menu led to a four-fold rise in these meals being chosen, which reduced the carbon footprint of the patient meal service. Recycling food packaging was also started, but there are challenges to widespread implementation. The project was successful, but it remains a starting point from which to increase food sustainability across the NHS and care sector catering provision.

Optimizing Local Materials in Green Roofs Through Citizen Science Activities at a Primary School in Azores

Green roofs are a fundamental technology in the transformation of urban centers into more sustainable environments, with a positive impact on buildings, cities, and their inhabitants. Yet, green roof technology may require the use of materials with a high environmental impact, namely, when associated with large transport distances. The present work arises from the need to find an environmental solution to use in an eco-school on one of the Azores islands. It tests green roofs on a wooden structure using local and sustainable materials. Prototypes were built to monitor their performance and to complement the theoretical information investigated regarding the construction systems of green roofs with alternative materials. The installation of the prototypes was accompanied by the school community, and the performance was monitored. The pumice stone proved to be an efficient solution for the drainage layer of the green roof. The use of local soil (volcanic origin) instead of a commercial substrate proved to work properly, both for drainage and for vegetation growth. Finally, the results also contribute to a better understanding of green roofs on wooden structures and encourage the use of local materials in future projects, with a view towards a circular economy.

Modular steel panel for walls: life cycle environmental impact, life cycle cost, and potential for material circulation

The impacts of civil construction are widely recognized and justify the transition from a linear to a circular economy. Furthermore, with building users increasingly demanding greater adaptability, strategies such as modularity and flexibility to adapt to changing uses are being discussed. Modular wall panels allow quick installation and have the potential for disassembly, refurbishment, reuse, and recycling. We evaluate a modular steel panel system in two Brazilian case studies through life cycle assessment (LCA), life cycle cost (LCC), and building circularity index (BCI). The study applies the circular reuse and remanufacture, recycling, and life extension strategies for internal and external walls. For the external panel, the life extension strategy (SE02) stands out positively in all impact categories, with the lowest environmental impact and costs. However, the SE02′s BCI does not have the best result. The second best option is reuse (SE03), with the highest percentage of circularity. Furthermore, the differences between SE02 and SE03 are reduced in several impact categories, and the sensitivity analysis (transport, damage, and the number of reuses) shows that the differences could be even smaller. For the internal panel, life extension (SI02) and reuse (SI03) scenarios are the best options. Recycling (SI04) has the highest environmental impact and the best potential for circularity. BCI communication must be aligned with LCA and LCC, such that an increase in circularity is accompanied by a decrease in environmental impacts or with infeasible costs, especially for developing countries.

Unlocking sustainable lithium: A comparative life cycle assessment of innovative extraction methods from brine

The surging demand for lithium, driven by the widespread adoption of electric vehicles and renewable energy storage systems, underscores the urgent need to develop sustainable lithium extraction methods. This study presents a comprehensive Life Cycle Assessment Using the TRACI method to evaluate and compare the environmental impacts of solvent extraction, adsorption, nanofiltration, and membrane electrolysis as direct lithium extraction methods for recovering lithium from brine to produce lithium carbonate. In terms of global warming, the carbon dioxide emission for each process was determined as follows: solvent extraction emits 52.7 kg CO2eq/kg of lithium carbonate, adsorption emits 47.9 CO2eq/kg of lithium carbonate, nanofiltration emits 17.7 kg CO2eq/kg of lithium carbonate, and membrane electrolysis emits 80.57 kg CO2eq/kg of lithium carbonate. As a result, the nanofiltration process emerges as the most environmentally friendly method, offering a promising solution to the environmental challenges of lithium extraction. In contrast, the membrane electrolysis process has the highest environmental impact.

Comparative Environmental Impact Assessment of Resistant Starch-Rich Pastas Produced from High-Amylose Soft Wheat or Malted Bean Flour

Flours rich in resistant starch (RS) are crucial for producing low glycemic index foods, as per Commission Regulation (EU) No. 432/2012. This study assessed the environmental profiles of two high-RS fresh pasta variants: one from malted and decorticated Gradoli Purgatory beans, and another from amylose-rich soft wheat flour, using the Product Environmental Footprint standard method. Both pastas had similar carbon footprints, but the overall weighted score of malted bean pasta was 38% higher than that of the high-amylose wheat pasta, making the latter more economically and environmentally viable. Climate change and water use were major contributors to their environmental footprints, influenced by cultivation practices. Mitigation strategies, such as cultivating drought-resistant beans, are recommended. Although greenhouse gas emissions per gram of protein or RS were similar, overall scores varied, emphasizing the need for sustainable crop selection. Consumer preferences may favor high-amylose wheat for glucose metabolism, while gluten-free, protein-rich needs can be met with malted bean flour, despite its higher environmental impact.

UAV Hunter: A Net-Capturing UAV System with Improved Detection and Tracking Methods for Anti-UAV Defense

The abuse of UAVs poses a potential risk to social security, necessitating the investigation of anti-UAV methods to safeguard critical areas. However, the existing UAV countermeasures face challenges such as high environmental impact, restricted spatial deployment, and low cost-effectiveness. To address these limitations, we developed a novel anti-UAV system known as UAV Hunter, which adopts an airborne tether-net capture device with visual aids to counter unauthorized UAVs. This system employs an “Anti-UAV with UAV” scheme, comprising a ground control station and a net-capturing UAV. The operator utilizes the ground control station to determine the mission area and flight path and then controls the flight of the net-capturing UAV. During flight, the net-capturing UAV leverages its dual-mode sensor to continuously monitor the target area. Simultaneously, the onboard computer executes a UAV detection and tracking algorithm to search for unauthorized UAVs in real time. The results are relayed to the operator in real time, facilitating precise adjustments for the net-capturing UAV to launch the rope net accurately. The system successfully realizes the functions of dual-mode real-time detection and tracking, precise net capture, and efficient integrated control. Compared with existing methods, the developed system exhibits accurate recognition, rapid action, diverse application scenarios, and an enhanced human–machine interaction experience. Test results in the open environment further validate the feasibility and functional integrity of the system, demonstrating its capability to effectively capture low-altitude unauthorized UAVs.

By-Products Valorization: Peptide Fractions from Milk Permeate Exert Antioxidant Activity in Cellular and In Vivo Models.

The discarding of agri-food by-products is a stringent problem due to their high environmental impact. Recovery strategies can lead to a reduction of waste and result in new applications. Agri-food waste represents a source of bioactive molecules, which could promote health benefits. The primary goal of this research has been the assessment of the antioxidant activity of milk permeate, a dairy farm by-product, and the isolation and identification of peptide fractions endowed with antioxidant activity. The chromatographic extraction of the peptide fractions was carried out, and the peptides were identified by mass spectrometry. The fractions showed radical scavenging activity in vitro. Moreover, the results in the Caco-2 cell model demonstrated that the peptide fractions were able to protect from oxidative stress by stimulating the Keap1/Nrf2 antioxidant signaling pathway, increasing the transcription of antioxidant enzymes. In addition, the bioactive peptides can affect cellular metabolism, increasing mitochondrial respiration. The action of the peptide fractions was also assessed in vivo on a zebrafish model and resulted in the protection of the whole organism from the adverse effects of acute cold stress, highlighting their strong capability to protect from an oxidative insult. Altogether, the results unveil novel recovery strategies for food by-products as sources of antioxidant bioactive peptides that might be utilized for the development of functional foods.

Comparative analysis of the bioaccumulation of bisphenol A in the blood serum and follicular fluid of women living in two areas with different environmental impacts.

Bisphenol A (BPA) is a common contaminant widely used in many industrial sectors. Because of its wide use and dispersion, it can be accumulated in living human bodies through both oral assumption and nondietary routes. BPA exhibits hormone-like properties, falling under the class of endocrine disruptors; therefore, it can alter relevant physiological functions. In particular, in women, it can affect folliculogenesis and therefore reproduction, contributing not only to infertility, but also to endometriosis and premature puberty. We conducted a multicenter study on 91 women undergoing a first in vitro fertilization (IVF) treatment in the Campania region (Southern Italy). We investigated the presence and concentration of BPA in serum and follicular fluids to assess the effects of airborne BPA contamination. The analysis was conducted on 32 women living in a low environmental impact (LEI) area, from the Sele Valley River and Cilento region, and 59 women living in a high environmental impact (HEI) area, the so-called "Land of Fires", a highly contaminated territory widely exposed to illegal waste practices. A higher average BPA content in both blood serum and follicular fluid was revealed in the HEI group when compared with the LEI group. In addition, we revealed higher average BPA content in blood serum than in folliclular fluid in the HEI area, with opposite average content in the two fluids in the LEI zone. In addition, our results also showed a lack of correlation between BPA content in follicular and serum fluids both in the overall population and in the HEI and LEI groups, with peculiar trends in different subsets of women. From our results, we revealed a heterogeneity in the distribution of BPA content between serum and follicular fluid. Further studies are needed to unravel the bioaccumulation mechanisms of BPA in highly polluted and nonpolluted areas.

Transforming the feeding regime towards low-input increases the environmental impact of organic milk production on a case study farm in central germany

Abstract Purpose Despite the direct effect of the feeding regime on the environmental impacts of dairy farming systems, its level of intensity, particularly in organic systems, has rarely been investigated. This study compares the environmental impact of a high-input feeding regime with a grassland-based, low-input feeding regime scenario within an organic milk production system conducted on Gladbacherhof, the research farm of Justus Liebig University Giessen, in Central Germany. Methods An integrated Life Cycle Assessment (LCA) analysis was performed from a cradle-to-farm gate perspective to quantify five environmental impacts, namely Global Warming (GW), Non-Renewable Energy Use (NREU), Land Use (LU), Terrestrial Acidification (TA), and Freshwater Eutrophication (FE). All agronomic data of the Gladbacherhof research farm, averaged over the years 2010–2017, were included. When not directly measured on the farm, ecoinvent data were included. Results and discussion Contrary to our hypothesis, the results suggest that a grassland-based low-input system has a higher environmental impact as compared to a high-input system for each of the five impact categories when using fat and protein-corrected milk (FPCM) as the functional unit. A 50% reduction in concentrates and exclusion of maize silage from the feed ration in the modelled low-input production system lead to a 20% drop in milk yield. To balance the energy content in low-input feeding ration, longer grazing period and higher amount of hay, alfalfa, and grass silage are required. This in turn results in higher emissions from enteric fermentation, manure management, and feed production and hence in higher environmental impact, particularly for GW, TA, and FE. Conclusions This study is one of the few that directly explores the environmental impact of feeding intensity in an organic milk production system. Nevertheless, there is a lack of research on consolidated emission factors for several greenhouse gas (GHG) sources in organic livestock and cropping systems to perform more robust carbon footprint calculations that comply with the Intergovernmental Panel on Climate Change (IPCC) Tier 3 GHG reporting guidelines. To generalize the results at the regional or national scale, direct comparisons with a larger number of organic farms representative of high-input and low-input intensities are still essential.

Assessing the aerobic/anoxic enrichment efficiency at different C/N ratios: pilot scale polyhydroxyalkanoates production from waste activated sludge

Polyhydroxyalkanoates (PHA) can be produced using fermentation products of an excess sewage sludge fermentation process. An efficient method to enrich a PHA-producing community is an aerobic-feast/anoxic-famine enrichment strategy. The effect of different carbon to nitrogen (C/N) feed ratios of 1, 2 and 3.5 g COD/g N on the process performance was studied. The study was executed on a pilot plant scale using fermented waste activated sludge as the organic carbon source. The system's performance was monitored in terms of removing contaminants, producing PHA, and reducing N2O emissions. The results indicated that a lower C/N ratio results in lower PHA production, with PHA content in the sludge of 20, 24 and 36 % w/w for C/N ratios of 1, 2 and 3.5 g COD/g N, respectively. At the lowest C/N ratio, the highest nitrite accumulation rate (77%), nitrification efficiency (89%) and denitrification efficiency (89%) were observed, but the N2O production was also the highest (0.77 mg N2O-N/L). The long-term comprehensive monitoring carried out in this study revealed high carbon and ammonia removal efficiencies (never below 80%) despite the C/N shifts and high COD and ammonia concentrations. At the same time, the system showed relatively low PHA production and high environmental impact in terms of high gaseous N2O emission. These findings question the sustainability of the aerobic-feast/anoxic-famine enrichment strategy for PHA production in full-scale plants.

Mass finishing of additively manufactured AISI 316L using pecan nutshells as sustainable abrasive media

Abrasive processes represent the main methods for obtaining high-quality surface finish in metal parts. As one main characteristic, these processes have a relatively high consumption of energy per material volume removed, as well as many inputs, such as abrasive tools and equipment, and, consequently, a high associated environmental impact. Additive manufacturing is becoming a competitive method to produce customized parts, but the surface finish is often not good enough for the application, and post-processing is needed. In this work, a mass finishing process using a planetary mill with abrasive media made of sustainable materials (pecan nutshells) was used on AISI 316L stainless steel samples manufactured by selective laser melting (SLM). The main goal was to perform a multicriteria analysis of the sample surface before and after post-processing. Through the analysis, it could be observed that the nutshell abrasive media has results close to those of traditional ceramic media. The increase in the rotation speed of the planetary mill, increase of finishing time, and use of abrasive pastes can further increase the effectiveness of the process.

Environmental performance of a multi-energy liquid air energy storage (LAES) system in cogeneration asset – A life cycle assessment-based comparison with lithium ion (Li-ion) battery

Increase in energy demand is shaping both developed and developing countries globally. As a result, the endeavour to reduce carbon emissions also encompasses electrical energy storage systems to ensure environmentally friendly power production and distribution. Currently, the scientific community is actively exploring and developing new storage technologies for this purpose. The focus of this work is to compare the eco-friendliness of a relatively novel technology such as liquid air energy storage (LAES) with an established storage solution such as Li-Ion battery (Li-ion). The comparison is carried out through Life Cycle Assessment (LCA) methodology which aims to assess the environmental impacts from each life stage, according to different impact categories. In particular, the study refers to the unitary storage and the delivery of electricity as well as cooling energy, considering all the inefficiencies and limits of each technology. The results show that in the full electric case study Li-ion battery environmentally outperform LAES due to (1) the higher round trip efficiency and (2) the significantly high environmental impact of the diathermic oil utilized by LAES, accounting for 92 % of the manufacture and disposal phase. Conversely, the cogeneration case study highlights that the “flexibility” and “dualism” of LAES, capable to efficiently deliver both electricity and cooling, offset the impact related to the higher electricity consumption during the use phase. Notably in energy mix frameworks with high share of primary energy source from fossil fuels, cogenerative LAES demonstrates superior environmental performance compared to Li-ion battery (i.e. 1302 kgCO2eq/MWhe vs 1140 kgCO2eq/MWhe for Singapore energy mix), attributable to its reduced electricity consumption.

What Environmental Metrics Are Used in Scientific Research to Estimate the Impact of Human Diets?

Metrics drive diagnosis, and metrics will also drive our response to the challenge of climate change. Recognising how current scientific research defines and uses metrics of the environmental impact of human diets is essential to understand which foods, food groups, or dietary patterns are associated with a higher environmental impact. This research, aided by artificial intelligence (AI), aimed to search, map, and synthesise current evidence on the commonly used definitions and metrics of the environmental impacts of human diets. We identified 466 studies measuring the environmental impact of diets. Most studies were from North American or European countries (67%), with data mainly from high-income countries (81%). Most studies did not include methods to recall the provenance of the foods consumed. Most (53%) of the studies only used one metric to estimate the environmental impact of human diets, with 82% of the studies using GHGE. Agreement on how the environmental impact of diets is measured and more comprehensive and accurate data on the environmental impact of single foods is essential to better understand what changes in food systems are needed, at a consumer and policy level, to make a well-meaning change towards a more sustainable diet.

Life cycle assessment of polysilicon photovoltaic modules with green recycling based on the ReCiPe method

Polysilicon photovoltaic (PV) modules are about to enter the end-of-life (EOL) stage on a large scale, and making the exploration of effective recycling methods and comprehensive evaluations their environmental impact through life cycle assessment (LCA) are key issues that need to be urgently tackled. In this study, we innovatively propose a recycling method utilising the green organic solvents 1,3-dimethyl-2-imidazolidinone (DMI) and deep eutectic solvent (DES). Additionally, an LCA of 1 m2 polysilicon PV modules - from industrial silicon production to waste recycling - was conducted using the ReCiPe 2016 method. The results indicate that the recycling process of polysilicon has the lowest environmental impact (1.02 Pt), whilst the production process has the highest environmental impact (4.22 Pt), leading to greater uncertainty. Sensitivity analyses showed that the sensitivity of the whole process was higher for electricity consumption and global warming (GW). Comparing the green organic solvent recycling to downcycling and landfill further demonstrates that environmental impact can be significantly reduced by employing this green organic solvent recycling approach, providing an important theoretical and practical pathway to promote the circular economy and sustainable development of the PV industry.