The impact of the discharge of the wastewater drains on to the sediments of the river Yamuna was studied. For this, eight important river sites in the Delhi stretch were identified and sediments samples were collected from these sites in the pre post-monsoon seasons. The sediments samples were analysed and compared for their organic matter, Porosity, Water Holding Capacity, Bulk Density and heavy metals concentration. Different pollution indices were used to classify the sites based on the levels of heavy metals observed in the sediments during both seasons. The obtained Contamination Factor values suggest low sediments contamination at the entry point of Yamuna river into Delhi and it follows the order of Zn > Cr > Co > Mn > Fe > Ni > Cu > Pb. This order modifies to Pb > Cr > Cu > Zn > Ni > Co > Mn > Fe for the sediments samples collected at the 29 km downstream from the reference point. The obtained values of the Pollution Load Index (PLI), Contamination Index and Enrichment Factor indicate that the sediments samples collected from the Yamuna river bed at the entry point of the river into Delhi have moderate degree of contamination. The level of contamination further increases in the Delhi stretch suggesting the impact of discharge of wastewater into Yamuna during the pre-monsoon season. However, PLI values suggest minimal level of pollution at all sediments collection sites during the post-monsoon season. Similarly, the bulk density of the sediments increased and water holding capacity, porosity and organic matter contents of the sediments decreased during post monsoon season indicating flushing of the Yamuna bed during the monsoon floods when the river velocity is high and a lot of turbulence and churning takes place.

The accurate measurement of pollutant baseline concentration is a crucial step for robust assessment, prediction and forecasting of air pollution in any region, especially in metro cities that witness extreme high level of pollution. The present study is an attempt to fill this gap and derive the baseline concentrations of two critical air pollutants, i.e., PM 2.5 and NO x in Delhi city. The study critically analyzes the data of winter period having consistent rainfall followed by complete weekend lockdown due to COVID-19. The findings indicate that the estimated baseline concentration is in the range of 20 - 36 mu g/m 3 and 12 - 63 mu g/m 3 for PM 2.5 and NO x (NO + NO 2 ), respectively during winter period of year 2022. The estimated baseline levels can be reasonably well compared with other reported values, both in the past studies as well as estimated using other referred methods. The baseline values are found higher in central areas of the city compared to outskirt located stations. The estimated baseline concentrations can be used in models for predicting the actual urban increment (actual increase in the source contribution with respect to the baseline), which will further help in decision making of target -oriented control actions.

An effective micro-level air quality management plan requires high-resolution monitoring of pollutants. India has already developed a vast network of air quality monitoring stations, both manual and real time, located primarily in urban areas, including megacities. The air quality monitoring network consists of conventional manual stations and real time Continuous Ambient Air Quality Monitoring Stations (CAAQMS) which comprise state-of-the-art analysers and instruments. India is currently in the early stages of developing and adopting economical portable sensor (EPS) in air quality monitoring systems. Protocols need to be established for field calibration and testing. The present research work is an attempt to develop a performance-based assessment framework for the selection of EPS for air quality monitoring. The two-stage selection protocol includes a review of the factory calibration data and a comparison of EPS data with a reference monitor, i.e. a portable calibrated monitor and a CAAQMS. Methods deployed include calculation of central tendency, dispersion around a central value, calculation of statistical parameters for data comparison, and plotting pollution rose and diurnal profile (peak and non-peak pollution measurement). Four commercially available EPS were tested blind, out of which, data from EPS 2 (S2) and EPS 3 (S3) were closer to reference stations at both locations. The selection was made by evaluating monitoring results, physical features, measurement range, and frequency along with examining capital cost. This proposed approach can be used to increase the usability of EPS in the development of micro-level air quality management strategies, other than regulatory compliance. For regulatory compliance, additional research is needed, including field calibration and evaluating EPS performance through additional variables. This proposed framework may be used as starting point, for such experiments, in order to develop confidence in the use of EPS.

Healthy indoor environmental quality in the offices is a key factor for good health and productive work output. The ventilation facilities, construction materials and design of the buildings are the key factors to influence the indoor environmental quality, i.e., thermal comfort and pollutant concentrations. The present study attempted to evaluate the indoor environmental quality of a newly renovated office building in Naraina Industrial area using sensor based monitors. The study measured PM2.5, relative humidity and temperature in different indoor micro-environments of the building including canteen area. The monitoring is carried out in indoor as well as outdoor environment using real time sensors based affordable monitor during one week period in September, 2022. The data analysis includes pollutant concentrations with and without operation of the ventilation system, indoor/outdoor ratio of pollutants, indoor air quality during working and non-working hours etc. The study also emphasized on the emission of pollutants due to cooking practices in the canteen area. The findings of the study highlight the effect of ventilation rate in the office building, office and canteen activities and infiltration of outdoor pollution.

The elevated levels of fine particulate matter (PM) and its associated health concerns are one of the major cause of apprehension for society as well as for policymakers in the region of Delhi-NCR. Atmospheric secondary aerosols are reported to hold one of the major fractions of PM. Considering its adverse effects and complex process of formation, the present article focuses on a critical review of its categorization based on formation mechanism, contribution to overall ambient aerosol load in the Delhi region, and other responsible factors. The formation of secondary aerosol is primarily governed by the abundance of precursor pollutants with variations in relative humidity, temperature, and solar radiation, which is evident in the seasons of post-monsoon and winter when there are higher emissions of NOx, SOx, NH3, VOCs, HCl, etc., which along with conducive meteorology, favor the increased rate of particle formation. The review reveals that secondary inorganic aerosols comprising of sulfate, nitrate, and ammonium contribute 24%, 15%, 21%, and 23% of PM10 during winter, summer, monsoon, and post-monsoon seasons, respectively, whereas the same is found to be higher in PM2.5, with 29%, 22%, 27%, and 28%. Thus, highlighting the need for comprehensive knowledge of secondary aerosol formation and its contributions in metropolitan areas such as Delhi, which will assist policymakers in determining the policies needed to curtail city-specific precursor factors, thereby reducing the ambient secondary aerosol concentration.

Air pollution has been a matter of grave concern since time immemorial but was brought to the attention of stakeholders only in the last few decades. The adverse repercussions of air pollution are still being observed, which have indicated uncertainties and gaps in existing management policies and control strategies. Hence, to reduce the detrimental consequences of air pollution, a more stringent and impeccable set of decisions that could govern the issue coupled with technological advancements is the need of the hour. The prerequisite for effective and efficient air quality management is to understand research gaps so far. The article attempts to provide information about the evolution of air quality management policies in India by collating data from the past studies compiled in a virtual repository called Indian Air Quality Studies Interactive Repository (IndAIR). The study also highlights the research gaps in the past studies and spatial distribution over the country map using the Geographical Information Systems (GIS). The gap analysis indicates that air pollution has been well studied in Indo-Gangetic Plains (IGPs), and metro cities. In contrast, Eastern, Southern, and the Central States are the least researched regions of the country. Further, the spatial distribution of PM2.5 and NOx concentrations are analyzed and found that highly polluted cities are studied more and vice versa. One of the least studied areas of various air quality domains is the socioeconomic effects of air pollution. Therefore, these regions and domains should be explored more closely to understand location-specific problems to tackle air pollution. The present review revealed several gaps, classified into three categories: research, policies, and economics.

The success of any policy intervention depends on its emission reduction potential, ease of enforcement, scale of implementation and socio-economic feasibility. However, all these parameters are not considered in an integrated manner in the air quality management practices followed in Indian cities. The existing policies are at the city-scale which turn out to be ineffective in addressing extreme air pollution problems at hotspot locations within a city. The present study is an attempt to develop a coherent framework for effective air quality management at identified air pollution hotspot. The study methodology includes sources information, data collection, emission inventorization, control scenario simulations using dispersion modeling, socio-economic assessment, ease of enforcement and ranking of the actions for implementation. The suggested process has been applied at an urban industrial area, (also identified PM2.5-APH) in Delhi city. Estimation of micro-level emission inventory in the surrounding area (2 km x 2 km) of the PM2.5-APH suggests highest anthropogenic emissions from road dust (45-56%) followed by multiple type of industries (18-21%). The maximum reduction in PM2.5 concentrations can be achieved by allowing industrial operations at full capacity during day-time only (24-40%) and road dust cleaning by mechanized vacuum machines (30-31%). An integrated criteria is developed for prioritization/ranking of control actions. The most effective actions are found to be i) mad dust cleaning by mechanized vacuum machine, ii) operation of industries with full capacity during day time only, iii) installation of cyclone dust collector in industrial stacks and iv) increase in stack height by 50%. This strategic framework can aid air quality managers in selection of the most suitable and appropriate policy interventions for an air pollution hotspot. Further, it can be replicated at other hotspot to prioritize the control actions for effective air quality management in any city.

Delhi megacity’s high level of air pollution is a grave concern and calls for stringent and result-oriented efforts toward its reduction to meet the specified standards. It is necessary to understand the effectiveness of control actions implemented in the past and their response to air quality. The present study attempts to compile the information on the implemented control strategies in the city and evaluate their response in terms of pollution reduction during the years 2003–2019. The pollutant concentrations data are analysed monthly and annually at selected three representative stations being operated for more than two decades. The Respirable Suspended Particulate Matter (RSPM) showed an increasing trend from 2003 to 2019, with an annual average increment in the range of 0.98–3.19%. The increment percentage was found more at Industrial sites compared to residential and commercial sites. The SO2 showed a decreasing trend with an annual reduction in the range of 1.49–4.09%. However, NO2 increased with an annual average of 5.21–6.07%. The reduction observed in the increasing trend of NO2 and RSPM in recent years after 2015 compared to previous years might be due to various source-specific, short-term and long-term control actions within the city and surrounding regions. The present analysis showed the impact of policy interventions on the air quality of Delhi city. However, there is a need to develop a systematic mechanism to monitor/assess the improvement in air quality (pollutant wise) due to implemented control strategies.

Critical assessment of spatio-temporal variations in pollution levels is a crucial step for identifying and prioritizing air pollution hotspots (APH) in urban areas. There is no universally accepted methodology for defining and delineating air pollution hotspot which can be source-specific, pollutant-specific and time-specific. The present research article is an attempt to develop a protocol for identifying APH for any pollutant within a city where-in three criteria-based innovative methodology has been derived. The three criteria are frequency of exceedance (% of days), scale of exceedance and consistency in exceedance (consecutive number of days) to the specified standards that need to be met continuously for at least three years. The suggested methodology has been applied on a three-year database (2018–2021) of 37 continuous ambient air quality stations to identify PM2.5 specific APH. The analysis indicates 11 APH in April, 9 in May, 2 in June and almost the entire city during the October–February months. Given prioritization of implementation of control actions, the identified APH during summer has been further physically examined to map source activity types and their suitability for ambient air quality monitoring stations as per the guidelines. The APH can be the priority areas for the implementation of control actions by urban local bodies. The management of air pollution at these priority areas would be more effective instead of city-scale management practice, which is difficult to implement and monitor.

The emergence of COVID-19 put pressure on the Governments of most of the countries in the world to enforce nationwide lockdown (restriction of all non-essential activities) to curtail the spread of infection. The nationwide lockdown created an adverse impact on the economies around the world and altered the day-to-day life of people. The restrictions on pollution generating activities during the lockdown period resulted in an overall improvement of the air quality throughout the world including India. This study evaluated the impact on air quality in 46 cities throughout India and the findings indicate that on average, PM2.5 and NOx, concentrations reduced by about 34% and 60%, respectively at different locations in India. PM2.5 concentrations reduced by about 23%, 16%, 32%, and 28% in small, medium, large and megacities, respectively. However, the reduction in NOx concentrations was dissimilar to PM2.5 in these cities. The findings further suggested that the impact of lockdown on air quality was not homogenous across the country and was probably due to varying background contributions. The average concentrations of PM2.5 and NOx at background stations were found higher in large and mega cities than the smaller cities. The PM2.5 concentrations at background stations were higher in North India in comparison to other parts of India.

Urban air pollution and exposure-related health impacts are being noticed and discussed very intensely in India. On the other hand, source-specific control is the primary focus for policymakers; however, diverse and complex sources make it difficult to immediately see the action and consequent impacts on better air quality. Many cities across the world have witnessed high air pollution levels at traffic junctions, more so in all Indian cities. Site-specific air pollution reduction can be a promising solution for managing the pollution level at highly polluted locations. CSIR-National Environmental Engineering Research Institute, India, has designed and developed Wind Augmentation and purifYing Unit (WAYU) to remove particulate and gaseous pollutants from urban hot spots such as traffic locations. In the present study, the authors attempted to evaluate the performance of two different designs of WAYU for the removal of particulate matters from polluted air at different traffic locations in Delhi City, the national capital territory of India. The performance analyses show that the current design of WAYU removes PM10 and PM2.5 concentrations in the range of 34–49% and 19–25%, respectively from the inlet air. The total PM collected from all WAYU devices was 34.19 kg from 120,557 operating hours’ at all the sampling sites. The PM removal rate depends on the size-segregated particulate matter pollution load in the ambient air.

Source apportionment studies are expected to provide relative contribution of different sources responsible for deteriorated air quality in an urban area, so that the agency responsible for urban air quality management can adopt prioritized source-specific control measures. Robust assessment of source contributions in a typical urban land-use pattern is the prime step for development of effective emission control strategies. This necessitates a critical review of the PM2.5 source apportionment studies conducted in different urban land uses and delineation of the dominant sources along with its contribution to reveal the diversifications among the peculiar land use classifications even within the same city. The present study reviewed the source apportionment studies carried out at 37 locations from seven Indian cities and categorized the sources contribution on seasonal (winters and summers) average basis for residential, commercial, industrial, kerbside, and mixed locations. The findings of the review studies inferred considerable variations in the source's contribution to air pollution with land use change. For example, during winter, domestic/biomass emission was reported as a significant source in residential (34%), commercial (26%), mixed (46%), industrial (31%), and road side (27%) locations in Delhi city in North India. However, vehicle (57%) was found to be the dominant source in residential area whose contribution increased up to 76% at road side location in Bangalore City in South India. It is also observed that source contributions vary in different seasons depending upon the activity levels. More or less similar observation was found in other cities selected for this study. The variations in source apportionment findings for a particular city might be attributed to heterogeneity of sources/major activity areas, nonuniform adoption of methodology. The study emphasizes on the need for the development of urban air quality management plan based on the land use specific source apportionment studies.

An air quality monitoring network (AQMN) having the ability to provide high spatial resolution real-time information is one of the key tools for developing management strategies for air quality improvement. National Environmental Engineering Research Institute (CSIR-NEERI) has deployed a Sensor-based Wireless Air Quality Monitoring Network (SWAQMN) to monitor real-time particulate matter (PM10 and PM2.5) concentrations in a highly urbanized megacity, Delhi, the capital of India. The sensors are equipped in a device, called Polludrone and located at ten locations covering different land use and source activities in the city. The Polludrone monitored data was compared with another calibrated PM monitor (GRIMM) for PM10. and PM2.5 concentrations and found a similar trend with correlation coefficient (r(2)) values of 0.73 and 0.85, respectively. The hourly average concentrations of PM10. and PM2.5 were found to be 446 and 242 mu g/m(3) by PM monitor, whereas the Polludrone recorded corresponding values as 314 mu g/m 3 and 176 mu g/m(3), respectively. Daily, diurnal and seasonal variability in PM a . and PM2.5 levels are analyzed at 09 locations in Delhi city using SWAQMN. Further, sensor's monitored data were compared with nearest located Continuous Ambient Air Quality Monitoring Stations (CAAQMS) in the form of Air Quality Index (AQI) and found the AQI values are comparable in all the four seasons. The sensor monitored low AQI values as compared to CAAQMS during monsoon and summer seasons. The present analysis suggests that the sensor-based network (low/affordable cost) can be successfully operated to get the real time air quality levels in an urban area.

Indoor air quality (IAQ) has drawn the attention of all the scientific community around the globe as it ranked one of the top five risks to public health throughout the world. People spend most of their time in indoor environments, be it in  their home or workplace, without knowing that they are inhaling substantially high concentrations of different indoor air pollutants (IAPs). In developing countries, IAP concentrations are generally found high due to poor ventilation and numerous indoor sources. Poor IAQ can adversely obstruct the mental, physical and social ability of a person, which can affect the working efficiency and result into loss in overall productivity. Along with other IAPs, high level of PM in indoor environments is one of the major concerns. The present study is an attempt to assess the exposure levels of PM10, PM2.5 and PM1 in one of the research laboratories, located in an industrial area of Delhi city. The monitoring is carried out at different indoor environments of the building. The preliminary results indicate that average concentration of PM10, PM2.5 and PM1.0 are highest in chemical laboratory, i.e., 114 ± 25 µg/m3, 58 ± 10 µg/m3, 33 ± 5 µg/m3, respectively and lowest at un-disturbed area, i.e., 42 ± 4 µg/m3, 33 ± 2 µg/m3, 22 ± 2 µg/m3, respectively. Ratio of PM2.5/PM10 and PM1.0/PM2.5 are found higher at un-disturbed area, i.e., 0.79 and 0.75, respectively as compared to other areas. It indicates that fine and ultra-fine particles travel more from outdoor compared to larger particle and suspend for longer time in the environment. Further, the study also discusses the possible measures to control the indoor air pollution and prioritize the indoor air-purifying plants based on their efficiency.

Numerous management strategies are implemented for the improvement in urban air quality worldwide, including control at tailpipe emissions. Control at the source is one of the best practices for pollution control, but this approach needs very stringent enforcement, public support, and monitoring for implementation. Besides, scientific processes-based technology to remove the pollutants from the ambient environment is also one of the approaches to improve air quality; however, high efficiency of such devices is one of the major challenges for the researchers. The present article is an attempt to review the state-of-the-art literature on such science-based technologies used to remove the pollutants from the ambient environment. The article highlighted the issues of high spatiotemporal variations in air pollution level in urban areas and methodologies available for the removal of pollutants. The efficiency of developed prototypes/devices using these processes is also compared worldwide. The technologies are available for particulate matter, and/or for gaseous pollutants. The air purification devices are designed and developed using scientific principles of bio-filtration, ionization, phytoremediation, photo-catalytic, and physical filtration. Based on the literature, it is found that ionization and physical filtration can remove particulate matter in the range of 61–95% and ~ 70%, respectively, while phytoremediation can remove in the range of 24–40%. The phytoremediation can remove NOx in the range of 10–15%. The efficiency of devices varies as pollution load and particle size distribution pattern varies. It is suggested that such control devices would be very useful in the reduction in air pollution at the hot spot area having high spatiotemporal variations.

Increasing air pollution levels in Delhi city is a major concern for regulators and stakeholders because of its associated critical and acute health impacts on human beings. During the onset of winter every year (in the months of October and November), people of Delhi were facing an increased level of pollutant concentrations from the last few years. The present study is an attempt to analyze the increased air pollution level episodic situation that occurred during 5–6th November 2016 in Delhi city. Four differently located air monitoring stations data on Air Quality Index, pollutant concentration, and meteorology from 25th October to 15th November 2016 are considered for the present analysis. The results indicate that PM2.5 concentrations exceeded 12–14 times whereas PM10 levels exceeded 8–17 times of NAAQS values of 60 µg/m3 and 100 µg/m3, respectively on 5–6th November 2016. The meteorological conditions were found worst for pollution dispersion on these two days which may be one of the reasons for high air pollution occurrence. However, NOx and SO2 concentration peaks were observed during Diwali days (Oct. 29–31, 2016). Critical analysis of the situation indicates that local sources are influencing the pollutant concentration significantly at the monitoring stations. Further, the qualitative evaluation of the graded response action plan (GRAP) indicates that the efficacy of a particular mitigation action on pollution reduction shall vary from site to site. Hence, in order to improve air quality in different zones, more emphasis needs to be given on regulating local activities as per suggested actions in addition to the regional level action plans.

INTRODUCTION:Open comminuted distal femur fractures are notorious for septic or aseptic non-union. The recommended fixed angle distal femur locking plate in such situations can lead to a septic non-union due to its extensive approach and further periosteal stripping. Supracondylar nails, though have a minimally invasive approach, are not suitable for type C2 and C3 (AO/ASIF) fractures. A monolateral fixator as damage control followed by plating may be recommended. But if wound healing is delayed it results in difficult articular reduction, poor alignment and a stiff knee. We therefore used ilizarov circular external fixators (ICEF) for such open fractures (type C1, C2 and C3) and analysed its radiological and functional outcomes.MATERIALS AND METHODS:25 male patients, with a mean age of 31.04 ± 6.62 years (range, 22-44 years), with open grade III type C distal femoral fractures were treated with ICEF. There were 7 fractures of type C1and C3 each, 11 were of type C2. Articular reduction and compression was achieved with inter-fragmentary screws through minimal open technique by extending the open wound and then stabilising the fracture with ICEF. The main outcomes evaluated were union, range of motion, final shortening, Knee Society scoring and ASAMI scoring system for radiological and functional outcomes.RESULTS:The mean follow-up period was 19.12 ± 1.14 months. All fractures except two united at a mean period of 30 ± 3.02 weeks, without the need of bone grafts. The bony assessment (according to ASAMI score) was excellent in 8 cases (33.33%), good in 9 cases (37.5%) and fair in 5 cases (20.83%), while there were 2 poor clinical end results. The functional results were excellent in 6 cases (25%), good in 9 cases (37.5%) fair in 6 cases (25%) poor in 3 cases (12.5%). The complications included shortening, extension lag and pin tract infections.CONCLUSION:With the encouraging results, the use of ICEF with minimal internal fixation in grade III open comminuted distal femur fractures as a primary definitive treatment is a valuable alternative.

High level of particulate matter pollution in the urban areas of major cities is significantly affecting the human health due to its toxic chemical constituents. Re-suspension of road dust along with tyre and brake wear are the dominant sources of PM pollution in the urban area in both developed and developing countries. This paper mainly reviews the contribution of road dust in ambient PM level, factors affecting re-suspension of road dust and chemical reagents available for dust suppression. The emission of road dust re-suspension significantly varies based on amount of silt deposited on the road, type of road (paved and unpaved road, concrete material of the paved road), number and types of vehicles movement. The chemical reagent such as calcium magnesium acetate, magnesium chloride and calcium chloride are reported to significantly reduce the PM emissions from road dust in developed countries. Therefore, the efficacy of these chemicals in reducing the road dust from the urban road in developing countries needs to be evaluated along with the cost–benefit analysis and comparison with the conventional approach of dust control (road cleaning and washing). However, the associated factors in different countries may vary significantly as compared to Western countries.

Delhi National Capital Region (Delhi NCR) is facing serious challenges linked to worrying levels of air pollution (mainly NO2, PM10 and PM2.5).The CADTIME prject (Clean Air in Delhi through Implementation, Mitigation and Engagement) aims to understand what is required to deliver significant reductions in levels of air pollution.This paper presents the results of the first stage of the project: it firstly contextualises the challenges of air quality management in Delhi within the broader evolution of environmental policies and governance in India, with particular consideration to the tensions between environmental protection and the country's development objectives.Secondly, it sets out how CADTIME will combine multiple source qualitative and quantitative data to develop an air quality action plan and an implementation strategy.In particular, through two workshops with local and national experts and stakeholders, and two rounds of focus groups with citizens of Delhi we will contrast stakeholders' priorities and preferences for existing and potential solutions to air pollution with citizens' lived experiences, thus assessing the political/technical feasibility and public acceptability of current and proposed measures.Furthermore, we will complement the primary qualitative data with a critical review examining the successes and failures of UK and European policies to draw lessons that can be relevant for Delhi and to avoid ineffective policies and achieve cost-effective solutions for the city in the shortest possible time.

Uncertainty/variability in measurement of NO2 in ambient air using Sodium Arsenite (SA) manual monitoring method (also known as modified Jacob & Hochheiser method) has been assessed through co-located sampling. Three sampling systems have been deployed and operated simultaneously for five days to find out variations in actual concentration determination. Significant variation in NO2 concentrations has been observed during sampling for 16 h (representing daytime activities) and 8 h (representing nighttime activities). Monitoring during co-located sampling showed considerable variation in flow rate, which can greatly influence the measured NO2 concentration, as in calculation a factor (82 %) for absorption efficiency of NO2 gas in absorption medium is used. At 0.5 l/min flow rate, the absorption efficiency for 8 h sampling is found to be about 69 %, which reduces to about 45 % at 1 l/min for the same sampling duration. Therefore, determination of actual NO2 concentration using this method at different conditions of flow rate and sampling duration may lead to under/over estimation of NO2 concentration, depending upon the specific sampling conditions, and may also affect decision making process involving this parameter. Further, efforts are made to minimize the variations in concentration determination through use of empirical relationships developed in laboratory studies carried out earlier by the present author. The variations are found to be reduced considerably after applying certain correction factors for absorption efficiency of NO2 due to sampling condition variations. This demonstrates the usefulness of lab scale experiments to the actual field monitoring scenario for appropriate decision making.