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The first European settlements in the new world faced technical issues with the help of the XVI century scientific advances. Besides briefly exposing the scientific and technological situation, this paper explores, with the help of reverse engineering, two singular mechanical wits representative of the technological advances introduced in America to overcome different problems. Firstly, a pump, based on an alternative movement system through crankshafts and pistons used against the continuous flooding suffered in the Ciudad de México valley. Although flooding remained a problem (it was solved in the XX century), hydraulic pumps were essential for continuous soil drainage. Secondly, a port crane for handling cannons, military devices, and construction materials during the Lima fortification in the XVII century. For both cases, reverse engineering, through engineering methods, Computer-Aided Design CAD programs, and additive manufacturing, provides virtual and/or tangible mockups that help to analyze and improve our knowledge about the dimensions, materials, and functions of used (and currently lost) mechanical systems during the American colonization. [ABSTRACT FROM AUTHOR]

Hybrid simulation (HS) is an experimental technique possessing advantages over other testing methods and, in several cases, it is the only available method to test structural systems with reliability. In this paper, HS is used to assess the effects of upgrading a soft-storey frame building using a Buckling-Restrained Brace (BRB). This topic is of paramount significance in seismic regions like Mexico, where more than 40 structures collapsed and thousands resulted with different levels of damage during the September 19, 2017 Mw 7.1 Earthquake. Unfortunately, one of the still-remaining challenges in many seismic countries is the use of seismic protective technologies (SPT) that help to mitigate damages in structures. With the aim of encouraging the use of SPT, this paper presents the results of an experimental program that shows the effectivity of buckling-restrained braces (BRBs) to improve safety and reduce damages in structures with one of the most typical causes of failure, i.e. the soft storey problem. A reinforced concrete five-storey frame building was selected first. Then, a numerical 2D model of the structure was subjected to nonlinear dynamic analyses using several earthquake ground motions. In many analyses, collapse was observed in the structure model. After that, the model was upgraded by introducing a BRB in the soft storey. HS was used to assess the performance of the upgraded structure under severe earthquake action. While the frame building was modelled numerically, the BRB was tested physically. The tests were repeated using a conventional brace instead of the BRB. The results show that introducing the BRB in the soft storey was an effective measure to improve the structure performance under seismic loading; while the disadvantages of the conventional brace were exposed. [ABSTRACT FROM AUTHOR]

In this paper, we analyze a massive dataset with registers of the movement of vehicles in the bus rapid transit system Metrobús in Mexico City from February 2020 to April 2021. With these records and a division of the system into 214 geographical regions (segments), we characterize the vehicles' activity through the statistical analysis of speeds in each zone. We use the Kullback–Leibler distance to compare the movement of vehicles in each segment and its evolution. The results for the dynamics in different zones are represented as a network where nodes define segments of the system Metrobús and edges describe similarity in the activity of vehicles. Community detection algorithms in this network allow the identification of patterns considering different levels of similarity in the distribution of speeds providing a framework for unsupervised classification of the movement of vehicles. The methods developed in this research are general and can be implemented to describe the activity of different transportation systems with detailed records of the movement of users or vehicles. [ABSTRACT FROM AUTHOR]

Alegoría de la construcción and Alegoría del trabajo were the first mural paintings commissioned to Saturnino Herrán (1887–1918), and they occupied a significant place in one of the most important schools in Mexico. The non-invasive methodology employed included different documentation phases and in situ multi-technique analyses. Hyperspectral imaging and digital radiography were used for a general characterization of the materials and were complemented with localized analyses by portable microscopy, and XRF and FORS spectroscopies. A complete identification of the original and the restoration palettes was achieved. Results from this work allowed us to understand the production context, painting technique, and conservation state, thus providing insights for the proper conservation of these murals, while also unveiling a new perception of the artist and his historical place among the muralist movement. [ABSTRACT FROM AUTHOR]

Acute respiratory infections (ARIs) are a major cause of morbidity and mortality among children. The causative pathogens show geographic and seasonal variations. We retrospectively evaluated the frequency and seasonality of respiratory pathogens in children and adolescents (age: 0–19 years) with ARIs treated between January 1, 2021, and March 31, 2022, at a single center in Mexico. Out of 2400 patients, 1,603 were diagnosed with SARS-CoV-2 infection and 797 were diagnosed with other common respiratory pathogens (CRPs). Of the 797 patients, 632 were infected with one CRP and 165 with > 2 CRPs. Deaths occurred only in SARS-CoV-2-infected patients. Rhinovirus/Enterovirus, respiratory syncytial virus B, and parainfluenza virus 3 were the most prevalent in cases with single and multiple infections. CRP showed a high frequency between autumn and winter of 2021, with higher incidence of hospitalization compared to COVID-19. The main comorbidities were immunosuppression, cardiovascular disease (CD), and asthma. The frequency of CRPs showed a downward trend throughout the first half of 2021. CRPs increased in single- and co-infection cases between the fourth and fifth waves of COVID-19, probably due to decreased nonpharmaceutical interventions and changes in diagnostic tests. Age, cyanosis (symptom), and immunosuppression (comorbidity) were found to differentiate between SARS-CoV-2 infection and CRP infection. [ABSTRACT FROM AUTHOR]

The quality of the urban environment is crucial for societal well-being. Yet, measuring and tracking the quality of urban environment, their evolution, and spatial disparities is difficult due to the amount of on-the-ground data needed to capture these patterns. The growing availability of street view images presents new prospects in identifying urban features. However, the reliability and consistency of these methods across different locations and time remains largely unexplored. We aim to develop a comprehensive index of urban quality and change at the street segment level using Google Street View (GSV) imagery. We focus on eight object classes that indicate urban decay or contribute to an unsightly urban space, such as potholes, graffiti, garbage, tents, barred or broken windows, discolored or dilapidated façades, weeds, and utility markings. We train an object detection model on a dataset of images from different cities and assess the performance of these urban indices. We evaluate the effectiveness of this method in various urban contexts over time and discuss its potential for urban planning and public policy. We demonstrate the use of these indices in three applications: the Tenderloin in San Francisco, the Doctores and Historic Center neighborhoods in Mexico City, and South Bend, Indiana. [ABSTRACT FROM AUTHOR]

In this paper, we consider several modelling approaches for the mean time between exceedances of a given environmental threshold. The interest here resides in the time between ozone exceedances (also called ozone inter-exceedances times). The proposed models assume two basic density functions for the time between surpassings: the Weibull and the generalised exponential functions. Considering those distributions, a random effect with autoregressive structure is taken into account to determine unexpected changes in the mean of the inter-exceedances density functions. Those unexpected changes could be captured either by their scale parameter or by both their scale and shape parameters. The models are applied to ozone data from the monitoring network of Mexico City. Selection of the model that best explains the data is performed using the deviance information criterion and also the sum of the absolute values of the differences between the estimated and observed means of the inter-exceedances times. An analysis to detect the possible presence of change-points is also presented. [ABSTRACT FROM AUTHOR]

In this paper we make use of some stochastic volatility models to analyse the behaviour of a weekly ozone average measurements series. The models considered here have been used previously in problems related to financial time series. Two models are considered and their parameters are estimated using a Bayesian approach based on Markov chain Monte Carlo (MCMC) methods. Both models are applied to the data provided by the monitoring network of the Metropolitan Area of Mexico City. The selection of the best model for that specific data set is performed using the Deviance Information Criterion and the Conditional Predictive Ordinate method. [ABSTRACT FROM AUTHOR]

Ozone air pollution is a serious problem in several cities of the world. Hence, to analyse the behaviour of this pollutant is a very important issue. One problem of interest is to study the behaviour of the inter-occurrences times between two ozone exceedances, i.e. between two days in which the pollutant's measurement surpasses a given threshold. Another interest resides in comparing the behaviour of ozone measurements in different seasons of the year. In this paper we use some Poisson models to analyse this problem. The time interval at which the ozone measurements were taken is split into subintervals corresponding roughly to the seasons of the year. We consider three parametric forms for the mean of the Poisson model, and consequently for the mean of the inter-occurrences times. In each model, the parameters describing its mean are estimated using Bayesian inference via Markov chain Monte Carlo methods. The models are applied to the ozone measurements provided by the Mexico City monitoring network. Theoretical results suggest that an increase has occurred in the mean inter-exceedances times and this is corroborated by the observed data. Differences between the behaviour of the pollutant during different seasons of the year are also detected as well as similarities in the same season in different years. Besides estimating the mean of the Poisson models, inference for the possible presence and location of change-points indicating change of parameters of the model is also performed. [ABSTRACT FROM AUTHOR]

The parameterization of the energy balance from a residential and commercial neighborhood of Mexico City was investigated using direct measurements of radiative and heat fluxes carried out during the MILAGRO/MCMA-2006 field campaign as a reference. The measured fluxes were used to evaluate different models of the energy balance based on parameterizations that require standard meteorological observations: ambient temperature, relative humidity, atmospheric pressure and cloudiness. It was found that these models reproduce with reasonable accuracy the diurnal features of the radiative and heat fluxes. The largest differences between modeled and observed fluxes correspond to the incoming longwave radiation, mainly due to errors in the cloudiness data. This paper contributes to the understanding of the energy partitioning in (sub)tropical urban environments, particularly in the developing world, where energy balance models have not been evaluated. [ABSTRACT FROM AUTHOR]

In many Third Wave democracies large classes of people experience diminished forms of citizenship. The systematic exclusion from mandated public goods and services significantly injures the citizenship and life chances of entire social groups. In democratic theory civil associations have a fundamental role to play in reversing this reality. One strand of theory, known as civic engagement, suggests that associations empower their members to engage in public politics, hold state officials to account, claim public services, and thereby improve the quality of democracy. Empirical demonstration of the argument is surprisingly rare, however, and limited to affluent democracies. In this article, we use original survey data for two large cities in Third Wave democracies-São Paulo and Mexico City-to explore this argument in a novel way. We focus on the extent to which participation in associations (or associationalism) increases 'active citizenship'-the effort to negotiate directly with state agents access to goods and services legally mandated for public provision, such as healthcare, sanitation, and security-rather than civic engagement, which encompasses any voluntary and public spirited activity. We examine separately associationalism's impact on the quality of citizenship, a dimension that varies independently from the level of active citizenship, by assessing differences in the types of citizenship practices individuals use to obtain access to vital goods and services. To interpret the findings, and identify possible causal pathways, the paper moves back-and-forth between two major research traditions that are rarely brought into dialogue: civic engagement and comparative historical studies of democratization. [ABSTRACT FROM AUTHOR]

In this paper, we use some non-homogeneous Poisson models in order to study the behavior of ozone measurements in Mexico City. We assume that the number of ozone peaks follows a non-homogeneous Poisson process. We consider four types of rate function for the Poisson process: power law, Musa-Okumoto, Goel-Okumoto, and a generalized Goel-Okumoto rate function. We also assume that a change-point may or may not be present. The analysis of the problem is performed by using a Bayesian approach via Markov chain Monte Carlo methods. The best model is chosen using the DIC criterion as well as graphical approach. [ABSTRACT FROM AUTHOR]

The article features chemist Mario Molina of Mexico City. It states that Molina won a Nobel Prize in Chemistry because of his postdoctoral research paper in 1974 which helped save the ozone layer and alarmed the world on atmospheric hazards caused by chlorofluorocarbons (CFCs). It adds that Molina has established the Mario Molina Center for Strategic Studies in Energy and the Environment in Mexico City to help Mexico City become the greenest megacity in Latin America.

We report the major highlights of the School of Cheminformatics in Latin America, Mexico City, November 24–25, 2022. Six lectures, one workshop, and one roundtable with four editors were presented during an online public event with speakers from academia, big pharma, and public research institutions. One thousand one hundred eighty-one students and academics from seventy-nine countries registered for the meeting. As part of the meeting, advances in enumeration and visualization of chemical space, applications in natural product-based drug discovery, drug discovery for neglected diseases, toxicity prediction, and general guidelines for data analysis were discussed. Experts from ChEMBL presented a workshop on how to use the resources of this major compounds database used in cheminformatics. The school also included a round table with editors of cheminformatics journals. The full program of the meeting and the recordings of the sessions are publicly available at https://www.youtube.com/@SchoolChemInfLA/featured. [ABSTRACT FROM AUTHOR]

Following the 1923 Kanto earthquake in Japan, Japanese researchers noticed the strong effects of surface geology on seismic motion (ESG) and began to investigate these effects to quantify the site amplification factors (SAFs) associated with soft surface sediments. On the other side of the Pacific Ocean, ESG received limited attention until the 1985 Michoacan, Mexico earthquake revealed significant long-period amplification inside Mexico City that manifested as the source of devastating damage to high-rise buildings. Since then, seismologists and earthquake engineers have performed a lot of studies on various ESG issues worldwide. We have not yet reached common conclusions on how to quantitatively predict SAFs over a broad frequency band of engineering interest, 0.1 to 20 Hz, for moderate to strong input from different types of earthquakes in different tectonic settings. However, we found here several basic guidelines useful for successfully modeling ground motions as a common approach to ESG studies. First, in this letter, we briefly review our history of understanding ESG, which is closely related to the key settings required for reliable quantifications of SAFs, and then introduce various emerging techniques for broadband quantitative evaluations of SAFs based on the vast amount of observed ground motions primarily from dense Japanese strong-motion networks. Based on the findings of our investigation and the physical relationships behind the parameters, the authors would like to recommend that researchers on ESG and related topics would refer to the five basic guidelines proposed in the conclusions for the successful implementation of techniques to delineate SAFs in a specific region of interest, such as the use of Fourier spectra instead of response spectra. We have started applying the proposed techniques to regions outside Japan. The implementation of the statistical validation exercises will follow. [ABSTRACT FROM AUTHOR]

Previous empirical studies on the correlation between residential burglary and concentrated disadvantage (CD) in Latin America commonly omit the spatial elements of the relationship. Using Mexico City (CDMX) residential burglary data for the period 2016 to 2018, we examine the predictive capacity of concentrated disadvantage in relation to residential burglary patterns, using a Geographically Weighted Regression approach to check whether their correlation varies across CDMX police quadrants. Controlling for relevant structural variables associated with residential burglary in previous studies, we find that the relationship between CD and residential burglary is positive in 844 out of 846 police quadrants (99.7%) and significantly much steeper in some quadrants than others –up to four times the median local slope. Thus, one key implication is that as this relationship is affected by spatial heterogeneity, traditional regression-to-the-mean analyses may misinform evidence-based crime prevention policies. [ABSTRACT FROM AUTHOR]

This article seeks to explain the multiplication of social environmental conflicts in Mexico as a consequence of expanding and intensifying extractive activities. It examines how the Mexican state has provided private and foreign capital greater access to the country's natural resources in the transition from state-led import-substituting industrialization to export-oriented market-led development. This, it argues, has led to accelerating material extraction rates in the context of rising global demand for primary commodities; while the negative environmental and social impacts have in turn led to a growing number of conflicts involving the inhabitants of directly affected rural communities, who organize to resist. Based on standardized procedures for material flow analysis, it presents the results of an investigation into the domestic extraction rates of minerals, metal ores, biomass, and fossil fuels from Mexico, between 1990 and 2018. It finds that domestic extraction rates increased significantly during this period, with the exception of fossil fuels, which peaked in 2006, declining thereafter due to the exhaustion of the country's most important oil reserves. The evolution of domestic extraction rates is juxtaposed with the emergence of related social environmental conflicts by drawing on multiple databases of conflicts around extractive activities in Mexico. [ABSTRACT FROM AUTHOR]

We report the main conclusions of the first Chemoinformatics and Artificial Intelligence Colloquium, Mexico City, June 15–17, 2022. Fifteen lectures were presented during a virtual public event with speakers from industry, academia, and non-for-profit organizations. Twelve hundred and ninety students and academics from more than 60 countries. During the meeting, applications, challenges, and opportunities in drug discovery, de novo drug design, ADME-Tox (absorption, distribution, metabolism, excretion and toxicity) property predictions, organic chemistry, peptides, and antibiotic resistance were discussed. The program along with the recordings of all sessions are freely available at https://www.difacquim.com/english/events/2022-colloquium/. [ABSTRACT FROM AUTHOR]

The results of a study of the elemental concentrations in PM10 samples collected at a site in southwest Mexico City during 2016 and 2019, are presented. The concentrations of up to 19 elements were measured with X-ray fluorescence (XRF). These analyses were complemented with ion chromatography for eight ionic species (for the samples collected in 2016). The behaviors of the gravimetric mass and elemental concentrations are described for the morning, afternoon, and night-time periods in 2019. The elemental concentrations observed in the PM10 samples did not present significant changes as compared to those published in previous works. It was found that the gravimetric mass concentrations were always below the official standards, except during a contingency period in May 2019. The positive matrix factorization (PMF) receptor model was used to identify contaminating sources and their relative contributions to the concentrations of the detected elements. The soil-related factors were the most abundant contributors, with other components associated to traffic, biomass burning, fuel oil, secondary aerosol, and dust resuspension. The occurrence of episodes in 2019 is explained with the aid of PMF and back-trajectories, while the contingency period is due to other chemical species not detected in PM10 with XRF. A comparison with data collected in 2005 in downtown Mexico City is also carried out, as well as with urban areas in other countries. [ABSTRACT FROM AUTHOR]

Cocaine use disorder (CUD) is a substance use disorder (SUD) characterized by compulsion to seek, use and abuse of cocaine, with severe health and economic consequences for the patients, their families and society. Due to the lack of successful treatments and high relapse rate, more research is needed to understand this and other SUD. Here, we present the SUDMEX CONN dataset, a Mexican open dataset of 74 CUD patients (9 female) and matched 64 healthy controls (6 female) that includes demographic, cognitive, clinical, and magnetic resonance imaging (MRI) data. MRI data includes: 1) structural (T1-weighted), 2) multishell high-angular resolution diffusion-weighted (DWI-HARDI) and 3) functional (resting state fMRI) sequences. The repository contains unprocessed MRI data available in brain imaging data structure (BIDS) format with corresponding metadata available at the OpenNeuro data sharing platform. Researchers can pursue brain variability between these groups or use a single group for a larger population sample. Measurement(s) functional brain measurement • Diffusion Weighted Imaging • Abnormality of brain morphology • Alteration Of Cognitive Function • Clinical Study Technology Type(s) Functional Magnetic Resonance Imaging • Diffusion Weighted Imaging • Turbo Field Echo MRI • neuropsychological test • Clinical Evaluation Factor Type(s) Cocaine Dependence Sample Characteristic - Organism Homo Sample Characteristic - Location Mexico City [ABSTRACT FROM AUTHOR]

Corruption has a significant impact on economic growth, democracy, and inequality. It has sever consequences at the human level. Public procurement, where public resources are used to purchase goods or services from the private sector, are particularly susceptible to corrupt practices. However, government turnover may bring significant changes in the way public contracting is done, and thus, in the levels and types of corruption involved in public procurement. In this respect, México lived a historical government transition in 2018, with the new government promising a crackdown on corruption. In this work, we analyze data from more than 1.5 million contracts corresponding from 2013 to 2020, to study to what extent this change of government affected the characteristics of public contracting, and we try to determine whether these changes affect how corruption takes place. To do this, we propose a statistical framework to compare the characteristics of the contracting practices within each administration, separating the contracts in different classes depending on whether or not they were made with companies that have now been identified as being involved in corrupt practices. We find that while the amount of resources spent with companies that turned out to be corrupt has decreased substantially, many of the patterns followed to contract these companies were maintained, and some of those in which changes did occur, are suggestive of a larger risk of corruption. [ABSTRACT FROM AUTHOR]

Light duty gasoline vehicles account for most of CO hydrocarbons and NOx emissions at the Metropolitan Area of Mexico City (MAMC). In order to ameliorate air pollution from the beginning of 2001, Tier 1 emission standards became mandatory for all new model year sold in the country. Car manufacturers in Mexico do not guarantee the performance of their exhaust emissions systems for a given mileage. The purpose of this study was to assess whether the Tier 1 vehicles will stand the certification values for at least 162000 km with the regular fuel available at the MAMC. Mileage accumulation and deterioration show that certified carbon monoxide emissions will stand for the useful life of the vehicles but in the case of non-methane hydrocarbons will be shorter by 40%, and nitrogen oxides emissions above the standard will be reached at one third of the accumulated kilometers. The effect of gasoline sulfur content, on the current in use Tier 1 vehicles of the MAMC and the impact on the emissions inventory in year 2010 showed that 31000 extra tons of NOx could be added to the inventory caused by the failure of the vehicles to control this pollutant at the useful life of vehicles. [ABSTRACT FROM AUTHOR]

Nopal (Opuntia ficus-indica) is widely cultivated in Mexico as a food raw material. However, the environmental impact caused by the growth and harvesting life cycle of this feedstock has been poorly studied. In this study, the environmental consequences of the growing, harvesting and transportation processes of nopal were evaluated with the aid of a life cycle assessment (LCA) method using SimaPro software version 8.5.2. The results showed that global warming (83.13%) and ozone depletion (99.25%) were significantly affected by the cultivation process due to current fertilization methods. The number of estimated gasses and chemicals emitted like ammonium (18.88 kgNH3/ha/year), nitrogen oxides (35.32 kgNOX–NO2/ha/year) and nitrous oxide (28.57 kgN2O/ha/year) were believed to be the result of the chemical fertilizers employed. The current cultivation process additionally reported emissions of nitrate (886.48 kgNO3/ha/year) and phosphorus (0.041 kg P/ha/year) caused by soil water erosion. The transportation process reported low levels of environmental impact; however, a significant amount of acidification (88.54%), mineral depletion (80.95%) and water consumption (84.06%) resulted from the process utilized to produce nopal in brine. In summary, the entire process resulted in a Global Warming Potential (GWP) of 0.562 kg/CO2 eq. [ABSTRACT FROM AUTHOR]

Background/objective: Changes in metabolism and extensive hemodynamic adjustments occur during normal pregnancy. The presence of maternal obesity imposes an overload to these physiological adaptations that may result in increased risk for the development of cardiometabolic complications during and after pregnancy. The aim of this study is to describe total cholesterol (TC), triglycerides (TG), glucose, and arterial blood pressure (BP) trajectories and to analyze the association of these cardiometabolic risk indicators during pregnancy with pre-pregnancy body mass index (pBMI) and monthly gestational weight gain (MGWG). Subjects/methods: A prospective cohort study of pregnant women was conducted in Mexico City. Monthly samples of blood were taken during clinical follow-up and biochemical and blood pressure were measured during each visit. Adjusted linear mixed-effect regression models were fit to describe the trajectories of these biomarkers during pregnancy and to analyze the association with pBMI and MGWG. Results: Seven hundred and twenty women were included of which 16.6% had pre-gestational obesity, 33.2% had pre-gestational overweight, 45.8% had normal pBMI and 4.4% had pre-gestational underweight. Women with pre-gestational obesity had higher lipids concentrations in the beginning of pregnancy (TC: β ̂ = 33.08, p = 0.010; TG: β ̂ = 31.29, p = <0.001) but the concentrations increased less than in women with normal pBMI (TC: β ̂ = −14.18, p = 0.001; TG: β ̂ = −5.42, p < 0.001). By the end of pregnancy, women with pre-gestational obesity had lower concentrations of lipids than women with normal pBMI. By contrast, women with pre-gestational obesity had higher glucose concentrations and higher BP levels than women with normal pBMI over pregnancy. Conclusions: pBMI is differentially associated with longitudinal trajectories of maternal biochemical markers of cardiometabolic risk. MGWG did not significantly affect the biochemical indicators or BP trajectories. Our results suggest that pBMI is more relevant to predicting adverse cardiometabolic markers trajectories during pregnancy than MGWG. [ABSTRACT FROM AUTHOR]

More than 7 thousand wildfires were recorded over Mexico in 2019, affecting almost 640 thousand hectares. Most of these fires occurred during the spring season generating dense smoke plumes, impacting urban areas in the central part of the Mexican plateau. From May 10 to 17, 2019, biomass burning (BB) plumes affected Mexico City (MC) and diffused across the basin, producing PM2.5 levels ~ 2 times higher than the nation's air quality standards. Average PM2.5 concentrations increased sharply from 29.4 ± 7.2 µg m−3 to 65.1 ± 13.6 µg m−3 when the dense smoke plumes were detected. The higher particle concentration impacted the aerosol optical depth (AOD) as values ~ 3 times greater than the annual mean (0.32 ± 0.12) were measured, which resulted in a 17% loss of global horizontal irradiation (GHI). Under these severe pollution conditions, the visibility (Va) was reduced by ~ 80%. The high incidence of strong absorbent particles, such as soot and tarballs was revealed through electron microscopy and X-ray fluorescence (XRF) analysis. These techniques show chemical similarities between MC aerosols and those from the high-altitude (~ 4010 m. a. g. l.) Altzomoni Atmospheric Observatory, evidencing a strong influence of the BB emissions, suggesting a regional transport of these pollutants. [ABSTRACT FROM AUTHOR]

Urban wastewater is a resource that can be reused, but its management must be carefully executed, considering its potential impact on public and environmental health. Unfortunately, marked differences in the quality of treatment, management, collection, and the monitoring of wastewater exist among low-, middle-, and high-income countries. This is the case of the Mezquital Valley, a semi-rural area that is composed of agricultural and industrial communities on the outskirts of Mexico City. For over 100 years, wastewater from Mexico City and its areas of conurbation has been sent to the Mezquital Valley, with few studies having been conducted to assess the existence and severity of bacterial and pathogen infiltration into the local aquifer. In this research, we present an assessment of wastewater infiltration transported from Mexico City, used for irrigation, with potential infiltration into the Mezquital Valley aquifer. We utilized stable isotope analysis of deuterium and oxygen-18 to determine whether a mixture of untreated wastewater from the Mexico City Metropolitan Area (MCMA) flows into the Mezquital aquifer. Also, tests for adenovirus, rotavirus, fecal coliform, fecal enterococci, Giardia lamblia, and Cryptosporidium parvum were employed to determine the presence of fecal indicators and pathogens in different water sources in the study area. The results show the presence of indicators and pathogens in local wells used as water supply in Mezquital Valley. The presence of such indicators suggests that pathogens can reach the water consumed by the inhabitants, posing a hazard to persons exposed to these waters during their normal daily-life activities. [ABSTRACT FROM AUTHOR]

Lower tropospheric thermal structure greatly affects atmospheric boundary-layer (ABL) stability and mixing processes with the free troposphere. In particular, in polluted urban zones, ABL stratification becomes a key variable in air quality research. This study focuses on generating a climatology (1990–2017) of the seasonal variability of ABL thermal structure in Mexico City by way of radiosonde analysis. Thermal inversion intensity and frequency are shown to be greater during winter and spring, a behaviour which coincides with greater pollutant concentrations. Higher concentrations are found during the dry season (November to May) than during the rainy months. In addition, significantly higher than normal surface pollutant concentrations are found on days with simple thermal inversion layers as well as during multilayer inversion days. Furthermore, stable layers, determined by potential temperature, are found throughout the year but more frequently during winter, whereas stable layers based on the virtual potential temperature prevail all year. In regions of complex terrain, such multiple stable layers have also been identified by previous authors. Additionally, the most unstable surface layers (in which the bulk Richardson number ( Ri B ) is small) develop during the rainy season, whereas during winter there are more levels in the vertical column with higher Ri B values. Although the Mexico City ABL and pollution episodes have been widely studied, this represents the first long-term investigation to consider the thermal stability of the ABL. Therefore, the present study provides a baseline for further research employing different observational techniques and high-resolution numerical models. [ABSTRACT FROM AUTHOR]

Background: This study aimed to determine whether crime patterns in Mexico City changed due to the COVID-19 pandemic, and to test whether any changes observed were associated with the disruption of routine activities, as measured by changes in public transport passenger numbers. Method: The first objective was assessed by comparing the observed incidence of crime after the COVID-19 pandemic was detected in the country with that expected based on ARIMA forecasts based on the pre-pandemic trends. The second objective was assessed by examining the association between crime incidence and the number of passengers on public transport using regressions with ARIMA errors. Results: Results indicated that most crime categories decreased significantly after the pandemic was detected in the country or after a national lockdown was instituted. Furthermore, the study found that some of the declines observed were associated with the reductions seen in public transport passenger numbers. However, the findings suggested that the changes in mobility explain part of the declines observed, with important variations per crime type. Conclusion: The findings contribute to the global evaluation of the effects of COVID-19 on crime and propose a robust method to explicitly test whether the changes observed are associated with changes in routine activities. [ABSTRACT FROM AUTHOR]

Negative impacts of environmental degradation and climate change are exacerbated when they co-occur in a single region, threatening people's way of life. In addition, historical and territorial processes generate a complex mosaic of interactions of residents and nonresidents, with a wide diversity of livelihoods. This generates a series of social, environmental and political conflicts in the territory. These conflicts have triggered an accelerated process of degradation, overexploitation and pressure on the Lacustrine Zone of Xochimilco (LZX). Therefore, research on how people's opinions and perceptions into decisions could help to generate a baseline for further collaboration. We documented the perceptions of nonresidents that are involved in decision making in the LZX in terms of degradation and climate change impacts and their opinions on the actions that could help strengthen the resilience of this area. According to our results, environment and culture were the most relevant features of the LZX, while social and institutional features were the most problematic ones. Additionally, nonresident actors emphasized the tendency of the LZX to collapse, which could become even more likely due to the impacts of climate change. To address these problems, restoring the "chinampa" type of production and implementing alternative tourism were the most frequently proposed actions, while training, involving stakeholders, and strengthening governance were the most frequently proposed strategies. [ABSTRACT FROM AUTHOR]

In large industrialized cities, tons of particles containing heavy metals are released into the environment and accumulate on street surfaces. Such particles cause a potential risk to human health due to their composition and size. The heavy metal contamination levels, main emission sources, and human health risks were identified in 482 samples of street dust. Heavy metal concentrations were obtained by microwave-assisted acid digestion and ICP-OES. The results indicated that street dust in Mexico City is contaminated mainly with Pb, Zn, and Cu, according to the contamination factor and the geoaccumulation index. The pollution load index of the street dust was made with the concentrations of Pb, Zn, Cu, Cr, and Ni. The main sources of Pb, Zn, Cu, and Cr are anthropic, probably due to vehicular traffic. The highest levels of Cr and Pb in urban dust represent a health risk for children. Contamination limits were proposed for heavy metals in street dust of Mexico City. These limits might be useful to generate and apply public policies to decrease anthropic emissions of the heavy metals studied, particularly Cr and Pb. [ABSTRACT FROM AUTHOR]

Notwithstanding the high societal impact of disasters in Mexico, there is a lack of integrated efforts to establish a sound policy for reducing disaster risk to counterbalance the existing concentrated endeavors in disaster management. In the face of such segmentation, the science and technology community has advocated for a change of perspective, from civil protection to integrated disaster risk management. The first Multi-Sectoral Conference towards Integrated Disaster Risk Management in Mexico: Building a National Public Policy (MuSe-IDRiM Conference) was held in Mexico City at National Autonomous University of Mexico, 21–24 October 2019. In support of the implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030, the conference aimed at enhancing the dialogue between the science and technology community, citizens, civil society organizations, private and public sectors, and the federal, state, and municipal governments to foster the process of transforming the current National Civil Protection System into a national public policy oriented towards integrated disaster risk management (DRM). Barriers and challenges to the implementation of integrated DRM were identified. Implementation of integrated DRM challenges current socioeconomic structures and encourages all relevant stakeholders to think, decide, and act from a different perspective and within and across spatial, temporal, jurisdictional, and institutional scales. Understanding disaster risk from an integrated approach, learning skills that authorities have not learned or used, and hence, strengthening disaster risk governance are prerequisites to effectively manage disaster risk. [ABSTRACT FROM AUTHOR]

This study aimed to validate the interferometric synthetic aperture radar (InSAR) method by using relative and absolute Global Navigation Satellite System (GNSS) techniques. In this context, two land subsidence areas, one high (Mexico City) and one medium (Aguascalientes), were monitored between 2014 and 2018 by using Sentinel 1A satellite data. The monitoring was carried out with the Small Baseline Subset (SBAS) technique using 46 images for Mexico City and 18 images for Aguascalientes. Concordantly, the GNSS Continuously Operating Reference Station (CORS) data in the regions were analyzed with relative and Precise Point Positioning (PPP) GNSS analysis techniques. The time series obtained from three different analyses were compared and the results were evaluated in light of statistical criteria. According to the results, it is determined that the InSAR-SBAS technique can vary up to ± 20 mm from the displacement values obtained from GNSS due to various noise sources. Such deviations were limited to a few samples, and in general the differentiations were reasonable in the range of 7–8 mm. The difference between the deformation velocity estimation results obtained from the three different methods varied between 3 and 10 mm/year. In this context, these findings suggest that the InSAR-SBAS technique is an effective method for monitoring land deformation with the accuracy of sub-centimeter decided. In addition, PPP which has become an increasingly popular technique showed fast and reliable results in the range of 5–10 mm for InSAR verification. Moreover, with this study, most current results for Mexico City, which is the world's fastest subsiding metropole, were achieved. In the central region of the city, the detected 300 mm/year of subsidence rate was updated as 370 mm/year. In addition, Aguascalientes was monitored by using the Sentinel 1A satellite mission for the first time in this study. The 60 mm/year subsidence rate obtained for Aguascalientes in previous studies was updated and it was estimated that there are zones where this rate reaches up to − 115 mm/year levels. In this regard, it was concluded that the deformation rate has increased for both regions since the previous monitoring studies. [ABSTRACT FROM AUTHOR]

The diurnal and seasonal variability of the mixed-layer height in urban areas has implications for ground-level air pollution and the meteorological conditions. Measurements of the backscatter of light pulses with a commercial lidar system were performed for a continuous period of almost six years between 2011 and 2016 in the southern part of Mexico City. The profiles were temporally and vertically smoothed, clouds were filtered out, and the mixed-layer height was determined with an ad hoc treatment of both the filtered and unfiltered profiles. The results are in agreement when compared with values of mixed-layer height reconstructed from, (i) radiosonde data, and (ii) surface and vertical column densities of a trace gas. The daily maxima of the mean mixed-layer height reach values >3km above ground level in the months of March-April, and are clearly lower (<2.7km) during the colder months from September-December. Mean daily minima are typically observed at 0700 local time (UTC − 6h), and are lowest during the winter months with values on average below 500 m. The data presented here show an anti-correlation between high-pollution episodes and the height of the mixed layer. The growth rate of the convective mixed-layer height has a seasonal behaviour, which is characterized together with the mixed-layer-height anomalies. A clear residual layer is evident from the backscattered signals recorded in days with specific atmospheric conditions, but also from the cloud-filtered mean diurnal profiles. The occasional presence of a residual layer results in an overestimation of the reported mixed-layer height during the night and early morning hours. [ABSTRACT FROM AUTHOR]

Pollen is an important cause of allergic respiratory ailments in the Mexico City Metropolitan Area (MCMA). However, very little is known if ambient air temperature correlates with the early blooming of plants observed in other urban areas around the world. A research study was conducted during the dry season of 2012-2013 at three representative sites of the MCMA with different urban characteristics with the aim to understand the relationships between the profusion and diversity of pollen against temperature and other meteorological variables and degree of urbanization. Pollen samples were collected using a Hirst-type trap sampler in the sites: Merced (highly urbanized), Iztapalapa (medium-high urbanized) and Coyoacan (moderately urbanized). Urbanization levels were determined using a composite index based on population density, proportion of surface covered by construction and asphalt, and urban heat island intensity. A set of representative pollen sampling tapes were assayed under a light microscope at magnification of ×1,000 and converted to grains per cubic meter. The most representative pollen types found in the three sites were, regardless of urbanization levels were: Fraxinus, Cupressaceae/Taxodiaceae, Casuarina, Alnus, Myrtaceae, and Pinus. Total pollen concentration was greatest in the moderately urbanized area, although earlier blooming took place at the highly urbanized zone. Total pollen concentration in the medium-high urbanized site has the lowest because the green areas in this zone of MCMA are few. In a diurnal basis, the most abundant pollen types peaked near midday or in the afternoon evening at the three sites. A Spearman test showed a positive correlation among bihourly pollen concentrations, temperature and relative humidity in all sites, but wind speed just correlated in Iztapalapa and Coyoacan. The results obtained suggest that Urban Heat Island Intensity can disturb flowering periods and pollen concentrations, largely in the highly urbanized areas. A principal components analysis established that the concentrations of each pollen type differed across the urbanization gradients. Additionally, it was found that a large number of allergenic pollens are produced by ornamental trees, some only recently introduced by urban planners. [ABSTRACT FROM AUTHOR]

Tillandsia recurvata is an epiphytic bromeliad with a wide distribution in the Americas; however, little is known about the development of its post-seminal adaptations for survival in epiphytic environments. The purpose of this study was to define the temperature and water requirements for the germination of T. recurvata seeds. The absence of radicle emergence in T. recurvata seeds resulted in 2 stages of germination: swollen with broken seed coat (stage-1) and chlorophyllic embryos (stage-2). The effects of partial or discontinuous hydration on germinated seed survival were also assessed. The seeds were collected in a semi-arid shrubland of Mexico City. We explored: (1) whether water vapour can provide a sufficient water source for germination; (2) the temperature required for germination stage-1 and the optimal and critical osmotic potentials for germination in both germination stages; (3) the effect of seed incubation at different osmotic potentials that undergo subsequent dehydration on their survival in stage-2; and (4) the loss of dehydration tolerance during early post-seminal development. In addition, an image of T. recurvata seed anatomy was obtained to illustrate its structures. Germination stage-1 of T. recurvata seeds is rather similar across the tested temperature range. The seeds required to be in contact with liquid water to germinate. The interval of osmotic potential facilitating both germination stages was from 0 to −0.6 MPa. Although germinated seeds displayed dehydration tolerance, this tolerance decreased in germination stage-2. The osmotic potential during germination affected the tolerance of the chlorophyllic embryos (stage-2) to subsequent dehydration. [ABSTRACT FROM AUTHOR]

Extreme alkalinity and salinity affects different processes involved in the N cycle, such as mineralization and nitrification, so it might affect the denitrification process and the N2O-to-N2 ratio. An alkaline saline soil of the former lake Texcoco with electrolytic conductivity (EC) 12.6 dS m−1 and pH 10.0, and an ‘extreme’ alkaline saline soil with EC 56 dS m−1 and pH 10.4 were amended with 100 mg NO3 − -N kg−1, purged of all O2, shaken and incubated anaerobically for 72 h. A ‘normal’ agricultural soil of Acolman with EC 0.8 dS m−1 and pH 6.3 was used as control. Treatments were with or without acetylene (C2H2) (found to inhibit reduction of N2O to N2) and with or without chloramphenicol (found to inhibit de novo synthesis of reduction enzymes), while emission of CO2 and N2O and concentrations of NO3 − and NO2 − were monitored. The NO3 − reduction rate was not affected by C2H2 or chloramphenicol in the Acolman soil, but decreased >3.5 times when chloramphenicol was added to the Texcoco soils. The concentration of NO2 − increased 3 times when chloramphenicol was added to the Acolman soil after 72 h, was similar in the Texcoco soil with EC 12 dS m−1, but chloramphenicol decreased it 14 times in the Texcoco soil with EC 56 dS m−1. The emission of N2O in the unamended Acolman soil was 0.09 mg N kg−1 and N2 6.5 mg N kg−1 soil after 72 h resulting in a N2O-to-N2 ratio of 0.014, while N2O production was 0.05 mg N kg−1 in the Texcoco soil with EC 12.6 dS m−1 and N2 1.6 mg N kg−1 resulting in a N2O-to-N2 ratio of 0.031. The emission of N2O in the Texcoco soil with EC 56 dS m−1 was 1.3 mg N kg−1 soil after 72 h and that of N2 was 2.0 mg N kg−1 resulting in a N2O-to-N2 ratio of 0.65. It was found that the activity of NO2 − and N2O reductase decreased with increased pH and EC, so that the concentrations of NO2 −, N2O and the N2O-to-N2 ratio increased with increased EC and pH, although that the effect of other soil characteristics can not be excluded. [ABSTRACT FROM AUTHOR]

Urban development has important implications for farmland preservation and natural resource management in local peri-urban communities. Social science research on recent changes in rural landscape of mega-cities tends to be limited to case studies in Latin-American nations. This study analyses the socioecomic dynamics of farming land use and the interactions between multiple cultural variables and the environment. Fieldwork was carried out during the 2002–2003 period in rural livelihoods of the five high mountain towns of south Mexico City. Data obtained from participatory survey and ethnographic techniques were integrated to assess changes in rural landscape and resource management and how urbanization, deforestation and market oriented agricultural production result in different livelihoods within a similar urban fringe context. The dynamic of mixture of urban and rural landscapes is based on farm productivity and social capital factors. The study concludes that policy support for regional agricultural production systems through enhancing ecosystems services, environmental protection and economic development is needed for sustainable development of local communities. [ABSTRACT FROM AUTHOR]

A remote sensing study was conducted in year 2006 in four locations of the Metropolitan Area of Mexico City (MAMC). Two of the sites were the same studied back by us in year 2000 and by others in year 1994. A database was compiled containing 11,289 valid measurements for the carbon monoxide (CO), total hydrocarbons (THC), and nitric oxide (NO) exhaust vehicles emissions. Valid measurements were binned for each pollutant by the vehicle specific power (between −5 and 20 kW tonne−1) for the 2000 and 2006 databases. The mean average CO, THC, and NO emissions for year 2006 were determined to be 1.10 ± 0.18 vol.%, 299 ± 88.4 ppm, and 610 ± 115.0 ppm, respectively. Matching the vehicle driving patterns of the fleet measured in year 2000 with the emissions factors obtained in this work, allows estimating the trends in the exhaust emissions of vehicles in the MAMC. The adjusted results of the remote sensing study performed in year 2006 shows that the fleet has decrease 22% in CO and 17% in NO emissions, with small change in total hydrocarbons emissions. The improvements could be related with the introduction in year 2001 of vehicles that met tighter emissions standards, particularly for nitrogen oxides. [ABSTRACT FROM AUTHOR]

This is a summary of the conversation among scholars attending the special session on "Responsibility, Opportunity, and Vision for Higher Education in Urban and Regional Carbon Management" at the First International Conference on Carbon Management at Urban and Regional Levels: Connecting Development Decisions to Global Issues in Mexico City Sept. 4-8, 2006. It includes The Declaration for Carbon Management Education, agreed upon by the participants. Obstacles to such a vision were discussed along with exemplar models of transdisciplinary curricula and suggestions for scholarship. [ABSTRACT FROM AUTHOR]

Study question: We examined whether methods for measuring exposure to airborne particles less than 10 µm in aerodynamic diameter (PM[sub 10]) in the Mexico City metropolitan area give different estimates of PM[sub 10] levels, and the nature of these differences, and developed a model for estimating missing PM[sub 10] data for one measurement method. Methods: Government PM[sub 10] measurements using two different technologies at five sites (the Sierra-Anderson PM[sub 10] HighVolume Air Sampler System, Hi-Vol) (every sixth day) and the Rupprecht and Patashnik Tapered Element Oscillating Microbalance (TEOM) monitor (daily), as well as Harvard Impactor (HI) data collected for research purposes from one monitoring station were matched by day and monitoring site, then compared visually and with basic descriptive statistics. We fit linear regression models with airport visual range measurements, meteorological data, and in formation on other air pollutants to predict the Hi-Vol measured PM[sub 10] levels for those days when direct measurements were not available. Results: We found relatively low correlations (r ranging from 0.46 to 0.63) between PM[sub 10] measured with the TEOM and Hi-Vol methods, and highly variable differences (0-70 µg/m³) between the means of these measurements, depending on monitoring site. The HI measurements had a relatively high correlation with the Hi-Vol measurements (r = 0.90). The models developed for the missing Hi-Vol measurements provided a series of estimated values similar to the actual Hi-Vol measurements, although the estimated series did not have high values in the range observed in the measured data. Conclusions: The differences we observed in the PM[sub 10] measurements across methods in Mexico City may be important when studying health effects associated with particle exposure, evaluating method performance under conditions and operating protocols similar to those in Mexico City, and determining compliance with... [ABSTRACT FROM AUTHOR]

The migration of scholars is a major driver of innovation and of diffusion of knowledge. Although large-scale bibliometric data have been used to measure international migration of scholars, our understanding of internal migration among researchers is very limited. This is partly due to a lack of data aggregated at a suitable sub-national level. In this study, we analyze internal migration in Mexico based on over 1.1 million authorship records from the Scopus database. We trace the movements of scholars between Mexican states, and provide key demographic measures of internal migration for the 1996–2018 period. From a methodological perspective, we develop a new framework for enhancing data quality, inferring states from affiliations, and detecting moves from modal states for the purposes of studying internal migration among researchers. Substantively, we combine demographic and network science techniques to improve our understanding of internal migration patterns within country boundaries. The migration patterns between states in Mexico appear to be heterogeneous in size and direction across regions. However, while many scholars remain in their regions, there seems to be a preference for Mexico City and the surrounding states as migration destinations. We observed that over the past two decades, there has been a general decreasing trend in the crude migration intensity. However, the migration network has become more dense and more diverse, and has included greater exchanges between states along the Gulf and the Pacific Coast. Our analysis, which is mostly empirical in nature, lays the foundations for testing and developing theories that can rely on the analytical framework developed by migration scholars, and the richness of appropriately processed bibliometric data. [ABSTRACT FROM AUTHOR]

Due to the availability of Web 2.0 technologies, volunteered geographic information (VGI) is on the rise. This new type of data is available on many topics and on different scales. Thus, it has become interesting for research. This article deals with the collective potential of VGI and remote sensing to detect peri-urbanization in the conservation zone of Mexico City. On the one hand, remote sensing identifies horizontal urban expansion, and on the other hand, VGI of ecological complaints provides data about informal settlements. This enables the combination of top-down approaches (remote sensing) and bottom-up approaches (ecological complaints). Within the analysis, we identify areas of high urbanization as well as complaint densities and bring them together in a multi-scale analysis using Geographic Information Systems (GIS). Furthermore, we investigate the influence of settlement patterns and main roads on the peri-urbanization process in Mexico City using OpenStreetMap. Peri-urbanization is detected especially in the transition zone between the urban and rural (conservation) area and near main roads as well as settlements. [ABSTRACT FROM AUTHOR]

The study of airborne metals in urban areas is relevant due to their toxic effects on human health and organisms. In this study, we analyzed metals including rare earth elements (REE) in particles smaller than 2.5 μm (PM2.5), collected at five sites around the Mexico City Metropolitan Area (MCMA), during three periods in 2011: April (dry-warm season, DW), August (rainy season, R), and November (dry-cold season, DC). Principal component analysis allowed identifying factors related to geogenic sources and factors related to anthropogenic sources. The recognition of the high impact of geogenic sources in PM2.5 is in agreement with the REE distribution patterns, which show similar behavior as those shown by igneous rocks, confirming the influence of the regional geogenic material. Metals associated to geogenic sources showed higher concentration (p < 0.05) at NE of the MCMA and a significant correlation with prevalent winds. Geogenic metals show similar seasonal distribution, with the highest concentration during DW (p < 0.05), suggesting a possible metal resuspension effect which affects more significantly at lower relative humidity (RH). The metals associated with anthropogenic sources are in agreement with the urban complexity of the area, showing homogenous distribution throughout MCMA (p > 0.05) and no similar seasonal pattern among them. These unexpected results exposed outstanding information regarding the identification of different geogenic sources as the main contributors of metals in the atmospheric environment in the MCMA and highlighted the importance of meteorology in the spatial and seasonal metal patterns. [ABSTRACT FROM AUTHOR]

The article analyzes the magnitude of raindrops. Results of a research conducted by Fernando García-García at the National Autonomous University in Mexico in Mexico City, Mexico showed that some raindrops fall by as much as an order of magnitude faster than their terminal velocity. Moreover, García-García also found out that the fragments continue to move faster than the mother raindrop for some time before slowing down to their own terminal speeds. The results could help climatologists improve the representation of rain physics in weather models.