City Of Athens Research Articles

Green Roofs as a Nature-Based Solution to Mitigate Urban Heating During a Heatwave Event in the City of Athens, Greece

Green Roofs as a Nature-Based Solution to Mitigate Urban Heating During a Heatwave Event in the City of Athens, Greece

Sensitivity Analysis and Parameterization of Gridded and Lumped Models Representation for Heterogeneous Land Use and Land Cover

Hydrological processes can be highly influenced by changes in land use land cover (LULC), which can make hydrological modelling also very sensitive to land cover characterization. Therefore, obtaining up-to-date LULC data is a crucial process in hydrological modelling, and as such, different sources of LULC data raises questions on their quality and applicability. This is especially true with new data sources, such as citizen science-based land cover maps. Therefore, this research aims to explore the influence of LULC data sources on hydrological models via their parameterization and by performing sensitivity analyses. Kiffissos catchment, in Greece, a poorly gauged and highly urbanized basin including the city of Athens, is the case study area. In total, 12 continuous hydrological models were developed by mainly varying their structure and parametrization (lumped and gridded) and using three LULC datasets: coordination of information on the environment (CORINE), Urban Atlas and Scent (citizen-based). It was found that excess precipitation is negligibly contributed to by soil saturation and is dominated by the runoff over impervious areas. Therefore, imperviousness was the main parameter influencing both sensitivity to land cover and parameterization. Lastly, although the parametrization as lumped and gridded models affected the representation of hydrological processes in pervious areas, it was not relevant in terms of excess precipitation.

Enhancing Sustainability: Quantifying and Mapping Vulnerability to Extreme Heat Using Socioeconomic Factors at the National, Regional and Local Levels

Population-dense urban areas often concentrate high commercial and industrial activity and intricate transportation systems. In crowded cities, extreme events can be even more damaging due to the high population they affect and the social inequalities that are likely to emerge. Extreme heat is a climate hazard that has been linked to high morbidity and mortality, especially in cities with high population densities. The way extreme heat events are felt in the population varies depending on a variety of factors, such as age, employment status, living conditions, air-conditioning, housing conditions, habits, behaviors and other socio-demographic parameters. In this article, we quantify and locate vulnerabilities of populations to extreme heat in order to formulate policy and practice recommendations that will make communities resilient and will shape the transition to a more sustainable future. This work contributes towards the achievement of Sustainable Development Goal 11—Sustainable Cities and Communities—by developing the tools to make cities and settlements resilient and sustainable. To this end, we analyze socioeconomic data at the NUTS3 level for the national case study of Greece and at the census tract level for the local case study of the city of Athens. The target variable for this study is defined as the average daily mortality during heatwaves per 100,000 individuals, and a methodology is developed for constructing this variable based on socioeconomic data available in public databases. The independent variables were selected based on their contribution to socioeconomic vulnerability; they include the percentage of elderly individuals, retirees, unemployed persons, renters, those living alone, those residing in smaller houses, those living in older houses and immigrants from developing countries. An ensemble gradient boosted tree model was employed for this study to obtain feature importance metrics that was used to construct a composite index of socioeconomic heat vulnerability. The socioeconomic heat vulnerability index (SHVI) was calculated for each prefecture in Greece and for each census tract in the city of Athens, Greece. The unique feature of this SHVI is that it can be applied to any geographical resolution using the same methodology and produces a result that is not only quantifiable, but also facilitates a comparison between vulnerability scores across different regions. This application aimed to map the SHVI of both prefecture and city, to examine the significance of scale, to identify vulnerability hotspots, and rank the most vulnerable areas, which are prioritized by authorities for interventions that protect public health.

Agent-based simulation model of micro-mobility trips in heterogeneous and perceived unsafe road environments

Safety concerns expressed by micro-mobility users seem to practically constrain the use and flexibility of these new modes. This paper introduces a new, parametric agent-based modeling approach for simulating micro-mobility, using MATSim as a platform. Perceived safety is introduced as a factor, which affects travel behavior of micro-mobility modes in a car-dominated, heterogeneous, and perceived unsafe road network. To meet the research objectives, different scenarios are simulated, using the city of Athens, Greece as a test bed, to examine the model performance and applicability. A universal scoring function based on travel time, cost, and safety, is proposed. This study also discusses the concept of unsafe discontinuities. Simulation results show that an unsafe road segment of 500 m long is sufficient to induce evident behavioral variations and hinder the practical use of e-bikes and e-scooters in the base scenario. The establishment of a cycle-friendly road network leads to significant changes in the chosen routes and decreases the average trip distance for micro-mobility users. In this case, the simulation process is guided by perceived safety, primarily focusing on formulating safer paths for micro-mobility mode users. Nevertheless, the routing behavior of car users is not modified due to the spatial uniformity of safety perceptions in a car-dominated road environment.

Innovative Strategies for Bio-Waste Collection in Major Cities during the COVID-19 Pandemic: A Comprehensive Model for Sustainable Cities—The City of Athens Experience

This paper introduces an innovative model for the organization and management of municipal bio-waste collection networks in major cities, particularly relevant in the context of the COVID-19 pandemic. Embracing circular economy principles and sustainable city practices, the proposed model addresses the urgent need for sustainable urban bio-waste management systems. Delving into the dynamic urban landscape, with a focus on the city of Athens, the study highlights the necessity of a robust decision-making methodology, the implementation of resilient processes, and the evaluation of their efficacy, especially during challenging times. The model centers on the effective collection, transportation, and monitoring of bio-waste, with a strategic aim to moderate environmental impacts, limit greenhouse gas emissions, and advance sustainable development goals. Utilizing the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, this paper thoroughly examines critical components of an innovative bio-waste collection network, including infrastructure, technology, and human resources. By merging best practices from global urban centers and accounting for the unique characteristics of Athens, the model envisions a transition toward a circular economy. Notably, the proposed municipal bio-waste collection network at the source anticipates substantial contributions to achieving Sustainable Development Goals in major cities. The study concludes by showcasing the successful application of these methodologies in the Municipality of Athens, providing tangible evidence of their positive impact.

Mapping the Potential of Zero-Energy Building in Greece Using Roof Photovoltaics

The present study investigates the incorporation of renewable rooftop photovoltaic systems in fully electrified residential buildings and estimates the zero-energy demand building potential in relation to the climatic data of Greece. Specifically, the aim of the analysis is to calculate the maximum possible number of stories and therefore the total building height for a complete transformation to zero-net-energy building. The energy analysis, which is conducted using the DesignBuilder software, focuses on single-floor up to seven-story buildings. The importance of the present work lies in the acknowledgment of the diversity of the Greek residential sector, the adherence to national energy policies, and the European goal of fully electrified buildings. The examined case studies are equipped with electrically driven air-to-air heat pumps serving the space heating and cooling demands and with an air-to-water heat pump covering the domestic hot water requirements. The investigated locations are the four main cities of Greece, Athens, Thessaloniki, Chania, and Kastoria, which represent the country’s four climatic categories. The conducted analysis allows for the mapping of the zero-energy building potential for the climatic data of Greece, demonstrating the possibility of striking a positive building energy balance through the integration of on-site renewable energy sources and the production of necessary electrical energy. The novelty of the present work lies in the identification of a key factor, namely, the building height, which determines the feasibility of transforming multifamily buildings into zero-energy buildings. According to the analysis results, the critical number of stories is calculated at six for Chania, five for Athens, four for Thessaloniki, and two for Kastoria. Regarding a three-story residential building, the incorporation of a renewable photovoltaic system can result in an annual surplus electricity production of 13,741 kWh (Chania), 10,424 kWh (Athens), and 6931 kWh (Thessaloniki), and a corresponding coverage of 100% (Chania), 69.0% (Athens), 38.9% (Thessaloniki) and 0% (Kastoria).

Athens as socio-material enactments: Experiencing the city through an art walk

In this article, I expand on the characterization of the city of Athens as a palimpsest. I embark on an analysis of the kaleidoscopic dynamics of the Greek capital, where contradictory elements can be traced. I draw on my ethnographic work on artistic practices in Athens to work towards a conceptualization of the city as multiple precarious enactments emerging simultaneously. As a way into this analysis, I follow an artistic guided walk, performed by the artist Aris Papadopoulos before an audience in the summer of 2020, throughout central parts of Athens. By describing scenes from this art walk, incoherencies emerge that, as I will argue, point to interfering and overlapping enactments of the same city. I adopt a science and technology studies approach to analyse how varying practices interweave into specific enactments. It is hoped that this approach can help us understand that no singular (and therefore reductive) representation of Athens is being sustained or promoted. Instead, it allows for inconsistencies and heterogeneous elements to come out and for silenced voices to be heard.

Ray-Tracing modeling for urban photovoltaic energy planning and management

The traditional Radiative Transfer Modelling solutions for Solar Energy monitoring and forecasting often provide outputs for a single point location or an area location. However, for high resolution representation of areas these solutions suffer due to low simulation speeds. This approach makes it difficult for decision-makers to accurately estimate the solar potential of the administrative area and plan installations accordingly. In this direction, the study introduces three-dimensional Ray-Tracing based radiative modeling which is a high-speed area-based solution for solar energy monitoring. The three-dimensional ray-tracing was simulated by using advanced graphic creation platforms and cloud computing in conjunction with satellite data of the clouds, aerosols, building shadows effects and three-dimensional representations of the city using Cesium 3D tiles and Unreal Engine ®. The entire system was developed in a hybrid model to be exploited by urban planners for solar PV installations and by electricity distribution system operators for energy management and efficient incorporation of the produced energy into the regular and smart grids. This study implements and analyses this Ray-Tracing model for solar photovoltaic energy potential estimation at a rooftop level for the city of Athens, Greece. The total rooftop exploitable area in Athens was found to be close to 34 km2, which is able to massively host distributed PVs followed by almost 4.3 TWh of annually produced energy, whilst Penteli (a Municipality in Athens) possessed a potential of 96.8 GWh with an exploitable area of just 0.8 km2. This amount of energy, in a hypothetical full coverage scenario, is able to provide for 48.7% of Athens’s total energy requirement. Similar year-long simulations were conducted using the EU’s largest rooftop solar installation at Stavros Niarchos Foundation Cultural Center and randomly selected rooftops having solar installations in different municipalities in Athens. With these estimated solar potential values, the gross savings in natural gas consumption and hence the CO2 equivalent emissions can be computed. With the current estimated solar potential of Athens, the analyzed savings accounted of nearly 2.43 billion euros and 18 MT CO2 equivalent emissions. These computed annual savings are capable of covering installation costs for nearly 100,000 new solar installations. The end-product of this study is the development of a solar cadastre web tool which will support the decision-makers in the energy transition policies and the solar PV penetration into the urban environment and eventually drive the effort into renewable energy transition across the globe.

Digital skills of and for lives marked by vulnerability: Being young, refugee, and connected in Europe

This article examines how teenage refugees in Europe develop digital skills in and through conditions of vulnerability. We argue that recognising vulnerability as a productive force, rather than merely as context, is crucial if we are to fully understand the emergence, limits and lack of skills among young people experiencing perpetual marginality. Drawing on 96 interviews and five creative workshops with teenage refugees in the cities of Athens, Brussels and London, we discuss three ways in which vulnerability and digital skills become entangled: (i) (dis-)connection, especially in conditions of scarce, interrupted and unsafe digital connectivity; (ii) learning, especially in contexts where digital and transnational literacies co-exist, compete or compensate for educational inequalities; and (iii) digital bordering, especially as this relates to restrictive regimes of mobility control that prolong risks for young refugees’ wellbeing and even life itself.

A Spatial Regression Model for Predicting Prices of Short-Term Rentals in Athens, Greece

Short-term house rentals constitute a growing component of tourist accommodation in several countries and the determination of factors affecting rents is an important consideration in relevant studies. Short-term rentals have shown increasing trends in the city of Athens, Greece; however, this activity has not been adequately studied. In this paper, spatial data of Airbnb rentals in Athens are analyzed in order to indicate the factors which are important for the spatial variation of rents. Factors such as property capacity, host attributes and review characteristics are considered. In addition, several locational attributes are examined. Regression analysis techniques are used to predict the cost per night, according to various explanatory factors, while the results of two models are presented: ordinary least squares (OLS) and geographically weighted regression (GWR). The results of the OLS model indicate several factors determining the rent, including capacity and host characteristics, as well as locational attributes. The GWR model produces more accurate results with a smaller number of independent variables. For the residuals analysis several additional amenities were examined that resulted in a small impact on rents. The unexplained spatial variation of rents may be attributed to neighborhood characteristics, socioeconomic conditions and special characteristics of the rentals.

Development of Experimental Low-Cost Rain Gauges and their Evaluation During a High Intensity Storm Event

The measurement of rainfall via ground sensors is fundamental in a variety of hydrological applications, including rainfall-runoff simulations, basin water balance and flood forecasting. The tipping bucket rain gauge (TBR) constitutes the most common type of automatic gauge for the measurement of rainfall intensity. The objective of this work is the development of low-cost and reliable rain gauges, including their data logger, which could be installed at remote, rural areas, in order to supplement with rainfall data the limited or non-existing network of hydrological stations. To achieve this target, two experimental TBRs with diameters of 20 cm (RG20) and 28 cm (RG28) were developed. Electronic boards Arduino UNO and Raspberry Pi were used for their data logger. The measurements of RG20 and RG28 were compared with those of a high quality rain gauge ARG100 and a daily non-recording rain gauge. The cyclone Daniel on 06-09-2023 caused an intermittent storm event in the city of Athens, Greece, which was measured by all three TBRs for purposes of evaluation. The results showed that the variations between ARG100 and RG28 were lower than 6%, while the variations between ARG100 and RG20 were about 10% during a few time intervals of high rainfall intensity. The return period of the storm event were estimated at 43, 59 and 45 years for rainfall durations of 10, 20 and 30 min, respectively.

Female Portrait Statuary in Roman-period Athens: the epigraphic and sculptural evidence

Female portrait statuary forms a large and important category of evidence for understanding the historical phenomenon of the visual representation and commemoration of women in the public spaces of the Greek city. With its rich body of both epigraphical and sculptural remains, the city of Athens is a particularly fruitful site to undertake such a study. While portraits of women begin to be set up in Athens in the early fourth century B.C., the chronological focus here is the Roman Imperial period, when inscribed bases for statues of women and marble sculpture representing female portrait subjects are the most abundant. I consider epigraphical evidence in the form of inscribed statue bases. The main sculptural evidence comes from the American excavations in the Athenian Agora. While a great deal of important research has focused on the epigraphic evidence, particularly from the Acropolis, this article analyzes and puts into conversation both strands of this extensive corpus of material.

The power of denial. From denial to creation: creative resistance in the city of Athens

The crisis leads to multiple denials in the face of everyday life and the conditions of reproduction of work it imposes. In this paper, I describe the basic denials in spaces of creative resistance in Athens during multiple crises. Through a systematic study of collaborative economy spaces, solidarity structures, and independent art spaces, I discern a progression of individuals from denial to creation and ultimately to action. I also strive to articulate the emerging modes of mobilization within these spaces. Faced with this reality, the act of denial emerges as the primary and transformative catalyst, sparking the forces of creativity and resistance. The denials of everyday life imposed by neoliberalism, as witnessed in Athens during the crisis, resulted in the creation of autonomous and self-organized spaces.

Athens Seen from Praeneste: Reforming the Image of the Prestigious City Sketched in Claudius Aelianus’ Miscellaneous Compilations

This article addresses the question of how the prestigious city of Athens, so central in the literary movement of the Second Sophistic, was represented in Claudius Aelianus’ miscellaneous compilations. These texts are the product of his readings and demonstrate the choices he made when selecting those facts that he thought worth remembering from the sources of which he made use. Therefore, the image of Athens reconstructed through the analysis presented in this article demonstrates how Aelianus refers to some well-chosen aspects of the city’s past and communicates them to his readers while reforming a specific image of the city. Indeed, the emphasis he uses when resorting to the use of literary practices, such as selection or collecting information, illustrates the cultural values of his time, characterized by a predilection for classical Athens.

Evaluation of energy consumption and electric range of battery electric busses for application to public transportation

Vehicle fleet electrification is the main target of the following decades, as a measure to decarbonize the transport sector. Electric urban busses consist of a solution for upgrading the bus fleet aiming to an improvement of urban areas and city centres air quality. To electrify the bus fleet at the city of Athens, Greece, the responsible organization, Athens Urban Transport Organization S.A. (OASA), organized a pilot program for using battery electric buses (BEB) in existing bus lines. The goal of the pilot program was to evaluate the energy consumption of the selected busses under real operation scenarios. The main target of this study is to describe the combined experimental and simulation methodology followed for the evaluation of the BEBs’ . The experimental part of the study is based on the monitoring of the BEBs under real operation for a specific bus line. During the operation of the vehicles, energy consumption along with environmental conditions and A/C usage were monitored. The simulation models were used to predict the energy consumption under different driving conditions and quantify the impact of operating parameters on energy consumption. Experimental results showed that the average daily energy consumption ranged between 96 kWh/km and 220 kWh/km, values strongly related to ambient temperature. Simulations highlighted that A/C usage can lead to two times higher energy consumption for the same route and load. Finally, the expected electric range of buses considered in the study calculated between 130 km and 170 km for the selected line, load equivalent of 25 passengers and 7 kW of A/C consumption.

Beyond linear regression: Modeling COVID-19 clinical cases with wastewater surveillance of SARS-CoV-2 for the city of Athens and Ohio University campus

Wastewater-based surveillance has emerged as a detection tool for population-wide infectious diseases, including coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Infected individuals shed the virus, which can be detected in wastewater using molecular techniques such as reverse transcription-digital polymerase chain reaction (RT-dPCR). This study examined the association between the number of clinical cases and the concentration of SARS-CoV-2 in wastewater beyond linear regression and for various normalizations of viral loads. Viral loads were measured in a total of 446 wastewater samples during the period from August 2021 to April 2022. These samples were collected from nine different locations, with 220 samples taken from four specific sites within the city of Athens and 226 samples from five sites within Ohio University. The correlation between COVID-19 cases and wastewater viral concentrations, which was estimated using the Pearson correlation coefficient, was statistically significant and ranged from 0.6 to 0.9. In addition, time-lagged cross correlation was applied to identify the lag time between clinical and wastewater data, estimated 4 to 7 days. While we also explored the effect on the correlation coefficients of various normalizations of viral loads accounting for procedural loss or amount of fecal material and of estimated lag times, these alternative specifications did not change our substantive conclusions. Additionally, several linear and non-linear regression models were applied to predict the COVID-19 cases given wastewater data as input. The non-linear approach was found to yield the highest R-squared and Pearson correlation and lowest Mean Absolute Error values between the predicted and actual number of COVID-19 cases for both aggregated OHIO Campus and city data. Our results provide support for previous studies on correlation and time lag and new evidence that non-linear models, approximated with artificial neural networks, should be implemented for WBS of contagious diseases.

High Resolution WRF Modelling of Extreme Heat Events and Mapping of the Urban Heat Island Characteristics in Athens, Greece

In recent decades, large-scale urbanisation has developed rapidly, resulting in significant changes in the local and regional environment and climate. Large metropolitan areas worldwide induce significant changes in local atmospheric circulation and boundary layer meteorology by modifying the underlying surface characteristics and through the emission of anthropogenic heat and pollutants into the atmosphere. We investigate the urban heat island (UHI) characteristics in the city of Athens, Greece, which is one of Europe’s largest metropolitan complexes with a population of approximately 3.7 million inhabitants. The UHI effect is intense due to the city’s size, dense construction, high incident solar radiation, and almost complete lack of natural vegetation, with previous studies suggesting a temperature rise of 4 °C on average in the city centre compared to summer background conditions. We used high-resolution WRF simulations (1-km horizontal grid) driven with ERA5 reanalysis data to produce surface temperature maps in the city of Athens and the surrounding areas (Region of Attiki) during the summer period of 1 July–20 August 2021. Different model parameterizations were tested, both with respect to urban characteristics and physical parameters. The daily minimum and maximum temperatures (Tmin and Tmax) derived from the model were validated against observational data from a dense network of weather stations covering metropolitan Athens and surrounding locations. We further investigate the influence of different meteorological conditions on the UHI gradients as produced by the model and the observational dataset, including the extreme heat wave of 28 July–5 August 2021, during which persistent maximum temperatures of >40 °C were recorded for nine consecutive days. The results indicate a strong correlation between WRF output and recorded minimum and maximum temperatures throughout the test period (R ranges from 0.80 to 0.93), with an average mean absolute bias (MAB) of 1.5 °C, and reveal the intensity and spatiotemporal variability of the UHI phenomenon in the city of Athens, with UHI magnitude reaching 8–9 °C at times. Our work aims to maximise the potential of using high-resolution WRF modelling for simulating extreme heat events and mapping the UHI effect in large metropolitan complexes.

Towards an urban ecosystem model through a cross-cultural Chinese and greek knowledge analysis

PurposeIn the post-pandemic era urban ecosystem planning has become critically important. Given the emphasis on relevant issues concerning the complex interactions between human civilizations and natural systems within urban environments in the new normal, this article aims to enrich the field of knowledge management developing a cross-cultural analysis for clarifying the role of knowledge in planning and urban ecosystems.Design/methodology/approachThis paper is conceptual in nature. Based on a theoretical foundation built by a critical literature review and data from the China Statistical Yearbook and China’s National Bureau of Statistics, this paper introduces some emerging real-impact topics regarding the connections between humanistic knowledge and urban planning. A comparative analysis between the capital city of Chang’an in the Tang dynasty of China and the capital city of Athens in Ancient Greek was used for explaining the influence of knowledge on successful urban planning.FindingsThe understanding the role of cross-cultural differences in knowledge management and practices for urban ecosystems offer the opportunities for rethinking consolidated approach to the interaction among social, economic, and environmental dimensions in urban settings.Originality/valueThis paper implies a new inter-disciplinary research field of great interest for the real impact KM community by illuminating how knowledge management is central in urban planning and across cultures.

Sustainable Supply Chain Management of COVID-19 Vaccines for Vaccination Delivery based on Routing Algorithms

Covid-19 pandemic has changed daily life in the city of Athens where vaccines are exploited with supply chain technology potentiality. Vaccines are tracked at the city’s airport till their delivery to vaccination centers. Due to the sensitivity of vaccines to the warm climate inherent in the city, delivery is assigned to a fleet of trucks. Specifically, two use cases, i.e., UC-I and UC-II, are proposed, which are based on global and local routing algorithms to exploit trucks’ load COVID-19 vaccine delivery from the airport and transport it to vaccination centers. In this paper, we focus on the supply chain routing algorithm technology of collecting COVID-19 vaccines from the airport and delivering them to vaccination centers in the smart city of Athens, Greece. Concretely, the purpose and the objectives of the research effort are in the areas of: (1) describing in deep detail the proposed supply chain system, (2) exploiting the adopted architecture based on certain separate use cases for system experimentation, (3) adopting specific vaccination routing algorithms to support vaccination distribution, and (4) evaluating experimentally the proposed supply chain system architecture with regards to the adopted use cases’ routing algorithms.

Allergic Rhinitis Systematic Review Shows the Trends in Prevalence in Children and Adolescents in Greece since 1990

Allergic rhinitis is the most common immune disorder worldwide, affecting approximately 10–40% of the general population. It is characterized by an inflammatory response of the nasal mucosa following exposure to non-infectious, inhaled, and airborne allergens that are defined based on the period of exposure to the allergen as annual, seasonal, or episodic. A variety of factors are found to relate to the prevalence of allergic rhinitis, i.e., sex, race, age, seasonality, personal and family-positive atopic history, as well as exposure to environmental and epigenetic factors. In addition to the local inflammation in the nasal mucosa, systemic inflammation is activated in the entire respiratory system, such as rhinoconjunctivitis, asthma, sinusitis, and otitis media with effusion. The aim of this study was to evaluate the trends in the prevalence of allergic rhinitis in the Greek pediatric and adolescent population since 1990. Research was performed in electronic databases (PubMed, ScienceDirect, and Cochrane Library) using appropriate MeSH terms for related studies from 1990 to 2023. We found 12 studies, 11 prospective and 1 cross-sectional, conducted in the cities of Athens, Thessaloniki, Patras and Evros prefecture, with sample sizes varying from 517 to 3076 subjects aged 6–17 years old. The prevalence of allergic rhinitis showed geographic and temporal variability, ranging between 2.1 and 32.5% in children and 25.3 and 30.8% in adolescents, with increasing trends. Factors such as gender (male), age (8–10 years), environmental exposures (moisture, mites, and fungi), positive atopic profile, and family history (asthma and eczema) were related to the manifestation of the disease. The need for systematic research in the Greek child and adolescent population is vital to recognize, prognosis, and control allergic rhinitis manifestations.