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The objective of the current study was to evaluate the chemical composition and the in vitro gas production (GP) of some non-leguminous forage trees in presence or absence of polyethylene glycol (PEG). Guazuma ulmifolia, Crescentia alata, Ficus glabrata, Ficus cotinifolia, Spondias purpurea, Mangifera indica, Licania arborea, Simira mexicana were collected during the rainy season, in the Bejucos locality, State of Mexico. Metabolizable energy (ME), partitioning factor (PF), in vitro organic matter digestibility (OMD), short chain fatty acids (SCFA) and microbial biomass production (MBP) were estimated as tools to detect the adverse effects of tannins in tree foliage. The chemical composition data were analyzed in a random design, and the in vitro digestion parameters on a randomized design with 8 × 2 factorial arrangement. Chemical composition showed a wide variation (P < 0.05) between species. The use of PEG increased (P < 0.05) GP from the foliage of S. purpurea, L. arborea, F. glabrata and G. ulmifolia, showing activity of total phenolics and condensed tannins. Similarly, ME (5.9 MJ kg DM), OMD (354.5 g kg DM) and SCFA (2.3 mol/150 mL) increased (P < 0.05); it was higher for S. purpurea, because of the PEG addition effect. The PF and MBP were different between species (P < 0.05), and decreased due to PEG addition (P < 0.05); the species with lower production was S. purpurea. It could be concluded that S. purpurea and F. cotinifolia represent important sources of fodder for livestock in the south region of Mexico. [ABSTRACT FROM AUTHOR]

The strategy for decreasing volatile organic compound emissions in Mexico has been focused much more on tailpipe emissions than on evaporative emissions, so there is very little information on the contribution of evaporative emissions to the total volatile organic compound inventory. We examined the magnitudes of exhaust and evaporative volatile organic compound emissions, and the species emitted, in a representative fleet of light-duty gasoline vehicles in the Metropolitan Area of Mexico City. The US 'FTP-75' test protocol was used to estimate volatile organic compound emissions associated with diurnal evaporative losses, and when the engine is started and a journey begins. The amount and nature of the volatile organic compounds emitted under these conditions have not previously been accounted in the official inventory of the area. Evaporative emissions from light-duty vehicles in the Metropolitan Area of Mexico City were estimated to be 39 % of the total annual amount of hydrocarbons emitted. Vehicles built before 1992 (16 % of the fleet) were found to be responsible for 43 % of the total hydrocarbon emissions from exhausts and 31 % of the evaporative emissions of organic compounds. The relatively high amounts of volatile organic compounds emitted from older vehicles found in this study show that strong emission controls need to be implemented in order to decrease the contribution of evaporative emissions of this fraction of the fleet. [ABSTRACT FROM AUTHOR]

Abstract: Recently a “Biofuels Promotion and Development Law” was approved in Mexico that requires increasing volumes of renewable to blend into the transportation fuel pool, much of which is likely to be ethanol. Emissions data under the three different driving conditions of the United States FTP-75 certification cycle were obtained for regulated, toxic and carbonyl compounds using recent model year vehicles representing 61% of the typical fleet available in Mexico. Ozone-forming potential and specific reactivity of tailpipe and evaporative emissions were also calculated. Comparison were performed using the traditional methyl-tertiary butyl ether employed in Mexico with an ethanol fuel at the same level of oxygen content, taking into account the current fuel specifications and the stream stocks available at the Mexican refineries. The results suggest that the contribution of cold start to regulated emissions range from 37% to 40% whiles those of toxic from 40% to 47% in both fuels. Results also indicate an increase in the rates of evaporative emissions of higher Specific Reactivy with the ethanol fuel. Estimation of the percent reduction of pollutants using the Complex Model of the USA Environmental Protection Agency suggests that volatile organic compounds will exceeds the limits imposed by the model if vapour pressure of the ethanol gasoline is not properly adjusted. [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]

Abstract: Most major metropolitan areas in Mexico have continually violated government health standards for ozone. Throughout this period policy plans have been developed for lowering urban ozone, and bringing cities into compliance with the law, among them, fuel reformulation. In this work, 12 fuels were prepared in several sets, to study the ozone-forming potential effects of individual fuel properties of Tier 0 and Tier 1 in-use vehicles of the Metropolitan Area of Mexico City. The results indicate that the specific reactivities for Tier 1 vehicles are in general much higher than those reported in similar studies performed by other groups. An emission inventory for the 2010year was calculated for each fuel in order to provide different scenarios for future formulations. [Copyright &y& Elsevier]

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]

Abstract: The level and nature of air pollution varies substantially from city to city. Hence, the first requirement is the creation of an adequate knowledge base on local air quality on which to develop an air quality policy. Because the availability of data used in traditional on-road mobile source estimation methodologies is limited in Mexico, an alternative methodology was implemented to estimate motor vehicle emissions. In the year 2000, on-road gasoline powered vehicle emissions in the Metropolitan Area of Mexico City (MAMC), were characterized using fuel sales as a measure of vehicle activity, and exhaust emissions factors from remote sensing measurements. In a similar way, remote sensing data obtained by researchers of the University of Denver back in 1991 and 1994 were used to estimate a fuel-based emission inventory for those years. Average emissions factors were estimated in 113.5±13, 13.1±1.9 and 9.84±2.3gl-1 for CO, hydrocarbons (HC) and nitrogen oxides (NOx), respectively, based on remote sensing measurements of 42,800 vehicles. For year 2000 light and medium gasoline vehicles exhaust emissions contributed with 2065, 238, and 179 metric ton day-1 of CO, HC and NOx, respectively. The inventory is 48% and 26% lower in CO and NOx, respectively, than official inventory estimates for the year 1998 using travel-based models. Calculated CO reduction from 1991 to 1994 is approximately 46% while the atmospheric CO measurements, as indicator of mobile activity, in the same period decrease 51%. For the period 1994–2000 the reductions were 36% and 31%, respectively. The calculations indicate a continually decreasing inventory over the study period, and represents and ideal alternative for locations such as Mexican cities lacking the resources to develop an emissions model. [Copyright &y& Elsevier]

A driving cycle derived from driving behavior and real traffic conditions in Mexico City (MC) is proposed. Data acquisition was carried out over diverse MC routes, representing travel under congested and uncongested conditions, using the chase-car approach. Thirteen different on-road patterns, including the four main access roads to MC, trips in both directions and different timetables, a total of 108 trips spanning 1044 km were evaluated in this study. The MC cycle lasts 1360 seconds with a distance of 8.8 km and average speed of 23.4 km h-1. Both maximum speed (73.6 km h-1) and maximum acceleration (2.22 km h-1 s-2) are lower than those of the new vehicles certification employed in Mexico , FTP-75 cycle., that is, the MC cycle exhibits less cruising time and more transient events than the FTP cycle. A total of 30 light duty gasoline vehicles were classified into different technological groups and tested in an FTP-75 and MC driving cycles in order to compare their emission factors A potential concern is that in Mexico manufacturers design vehicles to meet the emission standards in the FTP, but emission levels increase significantly in a more representative cycle of present driving patterns in the Metropolitan Area of Mexico City (MAMC). The use of a more representative cycle during certification testing, would provide an incentive for vehicle manufacturers to design emissions control systems to remain effective during operation modes that are not currently represented in the official test procedures used in the certification process. Based on the results of the study, the use of MC cycle, which better represents current day driving patterns during testing of vehicle fleets in emissions laboratories, would improve the accuracy of emissions factors used in the MAMC emissions inventories [ABSTRACT FROM AUTHOR]

The Inspection/Maintenance Program in the Metropolitan Area of Mexico City (MAMC) mandates a test every 6 months for allgasoline motor vehicles as one of the strategies to decrease emissions of vehicular pollutants. FTP-75 and ASM procedures were performed in our facilities to a fleet of 108 in-use motor vehicles before and after the approval of the I/M mandatory test. When our laboratorysimulated ASM data were compared with those of the official certificate, a large difference was observed between them. On the other hand, audits at the test-only centers indicate poor maintenance of the analytical instruments and dynamometers. On the basis of our FTP results, an estimation of the emissions change for the MAMC fleet shows a net 4% decrease in CO emissions, while total hydrocarbons and N0[sub x] increased 9 and 8%, respectively. Our results indicate that the I/M system in the MAMC lacks the technical capability and investment to ensure that software and hardware are properly maintained, calibrated, and upgraded. Sometimes limited attention is paid to ensure adequate training of inspectors, auditors, and quality control staff. [ABSTRACT FROM AUTHOR]

In the San Antonio Agricultural Center of Training and Sustainable Development, in the Chiapa de Corzo municipality, Chiapas State, Mexico, this study was developed with the objective of determining the effect of the use of forage trees on the ethological performance of cattle under intensive grazing conditions. Twelve young bulls wee used (Swiss x Zebu), with an average live weight of 157±3 kg, in a completely randomized design with two treatments (T1: Silvopastoral system) and T2: Monocrop system) and six repetitions. The herbaceous stratum was formed by Panicum maximum var. Tanzania, in both sites. Regarding the time the animals destined to the grazing activity, no significant differences were found between treatments. A lower temperature was observed during the morning and afternoon hours in the silvopastoral system (23,9 and 26,6 °C), as compared to the monocrop system (26,4 and 28,1 °C). Between the variables grazing and in situ temperature a negative correlation was found in both systems, but more remarkable in T2 (R=-0,41166-P=0,0003) than in T1 (R=-0,28453-P=0,0154). However, the growth rate showed significant differences (P<0,05) in favor of the silvopastoral system, with the best weight gains (486 g/animal/day), with regards to the animals under monocrop conditions (369 g/animal/day). [ABSTRACT FROM AUTHOR]

En el Centro Agropecuario de Capacitación y Desarrollo Sustentable San Antonio, en el municipio Chiapa de Corzo, Estado de Chiapas, México, se desarrolló esta investigación con el objetivo de determinar el efecto del uso de árboles forrajeros en el comportamiento etológico de bovinos en condiciones de pastoreo intensivo. Se utilizaron 12 toretes encastados (Suizo x Cebú), con un peso vivo promedio de 157±3 kg, en un diseño completamente al azar con dos tratamientos (T1: Sistema silvopastoril y T2: Sistema monocultivo) y seis repeticiones. El estrato herbáceo estaba formado por Panicum maximum var. Tanzania, en ambos sitios. Con relación al tiempo que los animales destinaban a la actividad de pastoreo, no se encontraron diferencias significativas entre tratamientos. Se observó una menor temperatura durante las horas de la mañana y la tarde en el sistema silvopastoril (23,9 y 26,6°C), en comparación con el sistema en monocultivo (26,4 y 28,1°C). Entre las variables pastoreo y tempera- tura in situ se encontró una correlación negativa en ambos sistemas, pero más marcada en el T2 (R=-0,41166- P=0,0003) que en el T1 (R=-0,28453-P=0,0154). Sin embargo, la tasa de crecimiento mostró diferencias significativas (P<0,05) a favor del silvopastoreo, con las mejores ganancias de peso (486 g/animal/día), en comparación con los animales en monocultivo (369 g/animal/día). [ABSTRACT FROM AUTHOR]

Highlights the contribution of the gasoline distribution cycle to volatile organic compound emissions in the metropolitan area of Mexico City, Mexico. Concentration of emissions in the gasoline transportation; Causes of organic compound emission; Measurement of organic compound emissions.

Linear infrastructures such as agricultural irrigation channels produce physical changes and negative impacts to habitats, wildlife populations, communities, and ecosystems. Open irrigation channels act as a pitfall for wildlife and can affect vertebrates of all sizes. Nonetheless, small channels have received relatively little attention by conservation biologists. The objective of this study was to analyze vertebrate species richness and mortality in relation to different sections of an irrigation channel system and the surrounding landscape characteristics. For two years, we conducted monthly surveys along an open-channel irrigation system to estimate its effect on vertebrates through records of dead and alive individuals. We examined the spatial relation of species richness and mortality with transects using a canonical correspondence analysis and chi-squared tests to determine possible variations in the different structures of the channel and seasonality. Further, a landscape diversity index was used to analyze the importance of surrounding habitat structure and composition on these parameters. Most vertebrates (61%) were found dead, small mammals and reptiles were the most affected. Our results indicate that mortality of small vertebrates varies depending on species, structures of the open-channel agricultural irrigation system ( i.e. , concrete channel and floodgates), seasonality ( i.e. , wet, and dry), and landscape heterogeneity ( i.e. , high, medium, and low landscape diversity). The open-channel irrigation system is a threat to populations of small vertebrates in anthropized landscapes, conservation efforts should be directed at protecting water bodies and restructuring the open-channel agricultural irrigation system to avoid mortality of species such as small rodents ( M. mexicanus ) and reptiles ( C. triseriatus , B. imbricata , and Thamnophis spp.)., Competing Interests: Armando Sunny is an Academic Editor for PeerJ., (©2024 Gómez-Ortiz et al.)

Background: Non-pharmacological interventions (NFI) or preventive actions (PA) are the best alternatives to control future pandemics, especially in vulnerable populations, such as semi-urban areas., Objective: To describe the predominant health behavior groups (HBG) and associated factors during the third wave of COVID-19 in a semi-urban area., Material and Methods: A survey which included characteristics, factors related to COVID-19, perceptions of health behavior and PA was applied in a probabilistic sample in a first-level hospital in the State of Mexico. People of both sexes over 18 years of age were included. Using a hierarchical cluster analysis, HBGs were obtained and characterized with a descriptive and multivariate statistical analysis., Results: In a probabilistic sample (n = 260), 4 HBGs were identified: 2 of high-risk (HRG) and 2 of low-risk (LRG), and the proportions were 43.5% y 56.5%, respectively. The sociodemographic characteristics of both groups were similar. Perceptions of severity and COVID-19-related barriers significantly influenced health behaviors in LRG. In HRG, low security played a significant role, highlighting the importance of comorbidities as a clinical factor., Conclusions: In a semi-urban area, 2 crucial health behaviors were identified: one associated with low risk and the other with high risk. In the HRG, the perception of insecurity was particularly relevant, emphasizing the importance of comorbidities as a clinical factor., (Licencia CC 4.0 (BY-NC-ND) © 2024 Revista Médica del Instituto Mexicano del Seguro Social.)

Background: Weight changes in adults have strong repercussions on people's health status. During the COVID-19 pandemic, these changes could be more evident due to the mandatory confinement, as well as eating habits and lifestyle. In this study, changes in diet and body weight in Mexican population at the beginning of COVID-19 lockdown period (weeks 4-7) were evaluated using an online survey., Objective: To identify the characteristics of the diet and the perceived change in body weight at the beginning of the COVID-19 pandemic in Mexico., Material and Methods: Descriptive, cross-sectional study of 1281 people over 18 years of age, electronic survey in weeks 4-7 of confinement with sociodemographic data, food consumption and perception of body weight., Results: The change in food consumption was 53.9%, finding differences according to gender in beverages (carbonated, juices, alcoholic), coffee/tea, fruits, legumes (p < 0.05). The perception of body weight increases by 3.4 (increased) and 2.1 (lowered) times more than the risk of change in diet., Conclusions: The dietary differences refer to a tendency to the type of food consumed, mainly sugary drinks, with the perception of changes in positive body weight in women., (Licencia CC 4.0 (BY-NC-ND) © 2023 Revista Médica del Instituto Mexicano del Seguro Social.)

Agave lechuguilla Torr., of the family Agavaceae, is distributed from southwestern United States to southern Mexico and is one of the most representative species of arid and semiarid regions. Its fiber is extracted for multiple purposes. The objective of this study was to generate a robust model to predict dry fiber yield (Dfw) rapidly, simply, and inexpensively. We used a power model in its linear form and bioclimatic areas as dummy variables. Training, generation (80%) and validation (20%) of the model was performed using machine learning with the package 'caret' of R. Using canonical correlation analysis (CCA), we evaluated the relationship of Dwf to bioclimatic variables. The principal components analysis (PCA) generated two bioclimatic zones, each with different A. lechuguilla productivities. We evaluated 499 individuals in four states of Mexico. The crown diameter (Cd) of this species adequately predicts its fiber dry weight (R2 = 0.6327; p < 0.05). The intercept (β0), slope [lnCd (β1)], zone [(β2)] and interaction [lnCd:Zona (β3)] of the dummy model was statistically significant (p < 0.05), giving origin to an equation for each bioclimatic zone. The CCA indicates a positive correlation between minimum temperature of the coldest month (Bio 6) and Dwf (r = 0.84 and p < 0.05). In conclusion, because of the decrease in Bio 6 of more than 0.5°C by 2050, the species could be vulnerable to climate change, and A. lechuguilla fiber production could be affected gradually in the coming years., Competing Interests: The authors have declared that no competing interests exist.

Pertussis is a highly contagious disease caused by Bordetella pertussis, which may be preventable by vaccination. There are two types of vaccines: whole-cell vaccines and acellular vaccines. Since pertussis control worldwide is heterogeneous, re-emergence of whooping cough has been observed in some countries. This re-emergence has been related to several factors: increased susceptibility to infection, better detection of disease, problems in obtaining adequate vaccination coverage, increase in susceptible subjects (mainly under 6 months of age), loss of immunity in adolescents and young adults, and likely genetic and adaptive B. pertussis changes. This paper discusses whole-cell and acellular vaccines' characteristics, advantages, and disadvantages. International recommendations are presented, and the participants' position is offered regarding the influence of the use of acellular vaccines and the potential disadvantages of reintroducing whole-cell vaccines, mainly due to their reactogenicity. Finally, strategies to achieve better control of pertussis in Mexico are discussed.

Background: Acute otitis media (AOM) is one of the most prevalent acute conditions in the pediatric population worldwide. This work aimed to elaborate a Clinical Practice Guideline with clinical recommendations systematically developed to assist decision-making of specialists, patients, caregivers, and public policymakers involved in managing patients with AOM in children., Methods: This document was developed by the College of Pediatric Otorhinolaryngology and Head, and Neck Surgery of Mexico (COPEME) in compliance with international standards. The SIGN quality of evidence classification was used. On behalf of the COPEME, the Guideline Development Group (GDG) was integrated, including otolaryngologists, infectologists, pediatricians, general practitioners, and methodologists with experience in systematic literature reviews and the development of clinical practice guidelines., Results: A consensus was reached on 18 clinical questions, covering what was previously established by the GDG in the scope document of the guidelines. Scientific evidence answering each of these clinical questions was identified and critically evaluated. The GDG agreed on the final wording of the clinical recommendations using the modified Delphi panel technique. Specialists and patient representatives conducted an external validation., Conclusions: This Clinical Practice Guideline presents clinical recommendations for the prevention, diagnosis, and management of AOM to assist shared decision-making among physicians, patients, and caregivers and improve the quality of clinical care., (Copyright: © 2022 Permanyer.)

COVID-19 affects the paediatric population less frequently than adults. A retrospective study was performed in a tertiary paediatric hospital in Mexico City in children <18 years of age who were hospitalized with a positive reverse transcription-polymerase chain reaction for SARS-CoV-2. Included in the study were 86 patients with a median age of 10 years old (IQR 2.6-14.3 years), who were classified in three groups: previously healthy, with chronic disease and immunosuppressed patients. The principal signs and symptoms were fever (81%), cough (51%) and headache (35%). A total of 20 patients (23%) required management in the paediatric intensive care unit (PICU) and 17% needed mechanical ventilation for an average of 12.7 days (IQR 2-29 days). There was no statistically significant difference between the three clinical classification groups in those patients admitted to the PICU, most of which were previously healthy patients. The mortality rate was 5% (four patients). Given that the paediatric population is susceptible to infection, potential transmitters and to clinical presentations with variable degrees of severity, it is important to continue reinforcing social distancing measures., (© The Author(s) [2021]. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

A clinical and entomological investigation was performed to identify flavivirus infections in humans and mosquitoes in impoverished areas of Guerrero, a coastal state in southwestern Mexico. A total of 639 patients with acute febrile illness and 830 resting female mosquitoes in low-income communities of Guerrero in 2019 were tested for evidence of flavivirus infection. Sera were collected from all patients and screened at a dilution of 1:20 by plaque reduction neutralization test (PRNT) using dengue virus (DENV)2. A total of 431 (67.4%) patients were seropositive. Sera from a subset of seropositive patients ( n  = 263) were tested for flavivirus NS1 by enzyme-linked immunosorbent assay. Forty-eight (18.3%) sera contained viral antigen. All NS1-positive sera were titrated and further tested by PRNT using DENV-1 to -4, St. Louis encephalitis virus, West Nile virus, and Zika virus (ZIKV). Seven patients were seropositive for DENV-1, five patients were seropositive for DENV-2, one patient was seropositive for DENV-3, and two patients each were seropositive for DENV-4 and ZIKV. The remainder had secondary flavivirus infections or antibodies to an undetermined flavivirus. Comparative PRNTs were also performed on 60 randomly selected NS1-negative sera, identifying patients seropositive for DENV-2, DENV-3, and ZIKV. The entomological investigation yielded 736 Aedes aegypti and 94 Culex quinquefasciatus that were sorted into 183 pools and 20 pools, respectively. Mosquitoes were assayed for flavivirus RNA by RT-PCR and Sanger sequencing. DENV-2 RNA was detected in three pools of A. aegypti . In summary, we provide evidence for the concurrent circulation of all four DENVs and ZIKV in Guerrero, Mexico. The public health authorities reported no cases of DENV-3, DENV-4, and ZIKV in Guerrero in 2019 and thus, we provide evidence of under-reporting in the region.

Objectives: The study sought to correlate fear, stress, knowledge regarding COVID-19 in Nursing students and recent graduates in Mexico., Methods: Correlational design, sample comprising 912 nursing students and graduates during the last 18 months from public and private universities of Mexico. To measure the variables, the study applied the instrument Fear of COVID-19 Scale, knowledge subscale of the scale Knowledge, attitudes, and practices towards COVID-19, and the instrument COVID Stress Scale., Results: Relationship was found of the age variable with fear, danger of contamination, traumatic stress, knowledge and minor socioeconomic consequences (p<0.05). Likewise, relationship was observed of fear with stress regarding COVID-19, danger of contamination, socioeconomic consequences, xenophobia, traumatic stress, and compulsive checking (p<0.05). Stress and knowledge explain the presence of fear regarding COVID-19 in 50.3%, and fear and knowledge explain stress regarding COVID-19 in 50.4%., Conclusions: Nursing students and recent graduates have high levels of stress and fear, besides low level of knowledge. The presence of high stress and low knowledge predict fear regarding COVID-19. Interventions are required on knowledge, stress, and fear regarding COVID-19 in the population studied., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright by the Universidad de Antioquia.)

A particular type of miniature ceramic vessel locally known as "veneneras" is occasionally found during archaeological excavations in the Maya Area. To date, only one study of a collection of such containers successfully identified organic residues through coupled chromatography-mass spectrometry methods. That study identified traces of nicotine likely associated with tobacco. Here we present a more complete picture by analyzing a suite of possible complementary ingredients in tobacco mixtures across a collection of 14 miniature vessels. The collection includes four different vessel forms and allows for the comparison of specimens which had previously formed part of museum exhibitions with recently excavated, untreated containers. Archaeological samples were compared with fresh as well as cured reference materials from two different species of tobacco (Nicotiana tabacum and N. rustica). In addition, we sampled six more plants which are linked to mind-altering practices through Mesoamerican ethnohistoric or ethnographic records. Analyses were conducted using UPLC-MS metabolomics-based analytical techniques, which significantly expand the possible detection of chemical compounds compared to previous biomarker-focused studies. Results include the detection of more than 9000 residual chemical features. We trace, for the first time, the presence of Mexican marigold (Tagetes lucida) in presumptive polydrug mixtures.

The energy reforms implemented in Mexico promote the use of ethanol in gasoline but exclude the country's ozone nonattainment areas oxygenated with methyl-tert-butyl ether (MTBE) in view that further scientific studies are required. To address a potential implementation scenario in areas of ozone high VOC-sensitive regimes, the impact on performance and emissions characteristics between the regular MTBE fuel available and a formulated gasoline containing 10% v/v ethanol having similar Reid vapor pressure (RVP) were compared in a single cylinder spark-ignited engine and a set of tier I vehicles. Included in the assessment were the "criteria" pollutants (THC, CO, and NO x ), toxic compounds, and speciated hydrocarbons in order to calculate the ozone-forming potential (OFP). The change in combustion speed of ethanol fuel vs. regular gasoline seems to be small and depends mainly on base gasoline formulation. Vehicle dynamometer testing showed no statistically significant differences in the average THC, CO, and NO x results when comparing both fuels. Statistically significant differences were seen in total speciated hydrocarbons, total carbonyls emitted, the increases in acetaldehyde emissions, and the decreases in OFP with E10. The results show roughly 20% increase in evaporative emissions when E10 is used, but the OFP of the emissions is lower than that of the Metropolitan Area of Mexico City fuel (MAMC). The increase in the oxygen content using ethanol fuel seems to have no deleterious effect on the vintage of vehicles tested. Taking into consideration that the evaporative emissions standard in Mexico is less stringent than that in other countries, the substitution of the actual regular gasoline for ethanol fuels should uphold the least volatile AA class in areas with ozone problems.

Introduction: Hybrids from species and subspecies of Mexican triatomines have shown outstanding biological and behavioral characteristics as compared with their parental groups. This could lead to an increasing risk of transmission of Trypanosoma cruzi to human and animal reservoir hosts., Objective: To describe and compare biological parameters related to the life cycle of Triatoma recurva, Meccus phyllosomus phyllosomus and their laboratory hybrids and estimate their risk as transmitters of T. cruzi to humans., Materials and Methods: We kept a cohort of each one of the three groups (T. recurva, M. p. phyllosomus and their hybrids) under similar laboratory conditions and then compared them to record the data related to their life cycles, number of blood meals to molt, mortality rates, egg eclosion rates and female fecundity., Results: The hybrid cohort showed the lowest mean time from first-instar nymph to adult (136.6 ± 17.5 days). The number of blood meals from molt to next instar (13.4 ± 1.7; 15.6 ± 5.2) was higher in the hybrid and T. recurva cohorts. The hybrid cohort showed the lowest mortality rate (29.5%) and the highest rate (70%) of adult females at the end of the biological cycle. Fecundity per day per female (range: 1.1 ± 0.6- 1.6 ± 0.7 eggs) was similar in the three cohorts. Egg hatching rate was higher than 70% in both hybrid and M. p. phyllosomus cohorts., Conclusion: The hybrid cohort showed some outstanding biological characteristics, which would entail a higher risk of transmission of T. cruzi to hosts than their parentals.

Species conservation and their management depend on the availability of their population behavior and changes in time. This way, population studies include aspects such as species abundance and activity pattern, among others, with the advantage that nowadays new technologies can be applied, in addition to common methods. In this study, we used camera-traps to obtain the index of relative abundance and to establish activity pattern of medium and large mammals in Sierra Nanchititla, Mexico. The study was conducted from December 2003 to May 2006, with a total sampling effort of 4 305 trap-days. We obtained 897 photographs of 19 different species. Nasua narica, Sylvilagus floridanus and Urocyon cinereoargenteus were the most abundant, in agreement with the relative abundance index (RAI, number of independent records/100 trap-days), and according to previous studies with indirect methods in the area. The activity patterns of the species showed that 67% of them are nocturnal, except Odocoileus virginianus, Nasua narica and others. Some species showed differences with previously reported patterns, which are related with seasonality, resources availability, organism sex, principally. The applied method contributed with reliable data about relative abundance and activity patterns.

Recently, the Mexican government launched a national program encouraging the blending of renewable fuels in engine fuel. To aid the assessment of the environmental consequences of this move, the effect of gasoline fuel additives, ethanol and methyl tert-butyl ether, on the tailpipe and the evaporative emissions of Mexico sold cars was investigated. Regulated exhaust and evaporative emissions, such as carbon monoxide, non-methane hydrocarbons, and nitrogen oxides, and 15 unregulated emissions were measured under various conditions on a set of 2005-2008 model light-duty vehicles selected based on sales statistics for the Mexico City metropolitan area provided by car manufacturers. The selected car brands are also frequent in Canada, the USA, and other parts of the world. This paper provides details and results of the experiment that are essential for evaluation of changes in the emission inventory, originating in the low-blend ethanol addition in light vehicle fuel.

In this work tailpipe and evaporative emissions from a set of normal and high emitter vehicle models, year 2006-2008 (low mileage) certified when new to meet the Tier 1 emission standard, were characterized for criteria pollutants (carbon monoxide, nitrogen oxides and hydrocarbons), and a suite of unregulated emissions including aliphatic and aromatic aldehydes, monocyclic aromatic compounds, 1,3 butadiene, n-hexane and acrolein. Data were obtained under the three different driving conditions of the United States Federal Test Procedure, FTP-75 cycle. High emissions of both regulated and unregulated pollutants were observed in the cold-start phase of the driving cycle for low mileage Tier 1 normal and high emitters engines. Data were compared with results obtained for a set of MY > 1992-2005 that included vehicles with no catalytic converters, Tier 0 and MY 2000-5 Tier 1 emission standard with high mileage. The calculated average cold-start emissions for normal emitters in grams are 0.93, 8.21 and 1.06 for NMHC CO, and NOx, respectively for Tier 1 low mileage vehicles. The reductions in emissions for Tier 1 normal emitters are 76%, 56% and 56% for NMHC, CO and NOx, respectively, but 58%, 30% and 25% for the high emitters. Differences in emission can be ascribed to the mileage accumulation more than technological improvements. Cold-start emissions account in the USA roughly 10% of emissions from gasoline-powered vehicles. In Mexico the fractions are likely to be higher because one must account also for the contribution of Tier 0 and the running exhausts emissions of vehicles with no catalytic converters.

Motor vehicle emission tests were performed on 12 in-use light duty vehicles, made up of the most representative emission control technologies in Mexico City: no catalyst, oxidative catalyst, and three way catalyst. Exhaust regulated (CO, NOx, and hydrocarbons) and toxic (benzene, formaldehyde, acetaldehyde, and 1,3-butadiene) emissions were evaluated for MTBE (5 vol %)- and ethanol (3, 6, and 10 vol %)-gasoline blends. The most significant overall emissions variations derived from the use of 6 vol % ethanol (relative to a 5% MTBE base gasoline) were 16% decrease in CO, 28% reduction in formaldehyde, and 80% increase in acetaldehyde emissions. A 26% reduction in CO emissions from the oldest fleet (< MY 1991, without catalytic converter), which represents about 44% of the in-use light duty vehicles in Mexico city, can be attained when using 6 vol% ethanol-gasoline, without significant variation in hydrocarbons and NOx emissions, when compared with a 5% vol MTBE-gasoline. On the basis of the emissions results, an estimation of the change in the motor vehicle emissions of the metropolitan area of Mexico city was calculated for the year 2010 if ethanol were to be used instead of MTBE, and the outcome was a considerable decrease in all regulated and toxic emissions, despite the growing motor vehicle population.

A 1999 ordinance by the Government of Mexico City bans 1993 model-year vehicles from on-road operation if their catalytic converters are not replaced with new ones. To validate the benefits of this action, we examined three issues related to exhaust emissions of vehicles equipped with catalytic converters. After selecting representative fleets of in-use vehicles, a comparison between emissions and catalyst efficiency in cars with two categories of exhaust emission limits was carried out. For that purpose, two fleets were selected, each made up of 10 vehicles run under similar conditions. A third, larger fleet with emissions control systems was used to evaluate and simulate real-world conditions of vehicles in a controlled laboratory. Finally, the aging effect on the catalytic converter was studied on vehicles run for 100,000 km, replacing their old emission control devices for new ones. The 1991-1992 model-year vehicles showed a high percentage of compliance with the corresponding emissions standard (90%) in comparison with 1993 model-year and later vehicles (Tier 0). However, NOx emissions were higher for the newer vehicles. Fifty percent of the 1991-1992 model-year vehicles evaluated under the official inspection/maintenance (I/M) procedure did not meet the regulated emissions standard when the results were compared with those of the U.S. Federal Test Procedure FTP-75. Our results suggest that the replacement of old catalytic converters with new ones will have little effect on decreasing polluting emissions because these vehicles were in very bad mechanical condition. Results of catalytic activity as a function of mileage indicated inefficient catalyst performance for the fleets tested. All pollutant conversions were below 90% efficiency, and they deteriorated by an average of 30% after the vehicles were run for 100,000 km.

Measurements of hydrocarbon (HC) emissions generated by the use of liquefied petroleum gas (LPG) in the metropolitan area of Guadalajara City (MAG) are presented in this work. Based on measurements in the course of distribution, handling, and consumption, an estimated 4407 tons/yr are released into the atmosphere. The three most important contributors to LPG emissions were refilling of LPG-fueled vehicles and commercial and domestic consumption. The MAG shows a different contribution pattern of LPG emission sources compared with that of the metropolitan area of Mexico City (MAMC). These results show that each megacity has different sources of emissions, which provides more accurate strategies in the handling procedures for LPG to decrease the impact in O3 levels. This work represents the first evaluation performed in Guadalajara City, based on current measurements, of the LPG contribution to polluting emissions.

In this work, the primary objective was to assess the impact of oxygenated fuel on the exhaust emissions from an important fraction of vehicles in the Metropolitan Area of Mexico City (MAMC). The results aim to provide information on the actual effect of MTBE on a fleet that represents more than 60% of the in-use vehicles in the MAMC. Ten vehicles were tested with a low-octane base gasoline, and 10 more with a regular-grade unleaded base gasoline. Three MTBE concentrations, 5, 10, and 15 vol %, were tested following the U.S. Federal Test Procedure (FTP). CO, total HC, and NOx from the exhaust gases were quantitatively evaluated and also characterized for FTP speciated organic emissions. From this data, the O3-forming potential of the fuels was calculated. Results show that for the fleet using low-octane gasoline, the addition of 10% MTBE substantially reduced CO emissions, but total HC concentration in the exhaust showed a modest decrease. For the regular gasoline, the 10% MTBE blend seemed to be the best choice, but there was not a significant decrease in emissions. The specific reactivity of each fuel, expressed in grams of O3 per gram of nonmethane organic gases, increased with MTBE concentration in both cases. This result is important to consider, especially for a region like Mexico City, which has high atmospheric O3 concentrations.

An estimation of hydrocarbon emissions caused by the consumption of liquefied petroleum gas (LPG) in the Metropolitan Area of Mexico City (MAMC) is presented. On the basis of experimental measurements at all points of handling, during the distribution process, and during the consumption of LPG in industrial devices and domestic appliances, an estimated 76,414 tons/year are released to the air. The most important contribution is found during the domestic consumption of LPG (70%); this makes the control initiatives available to the consumer. By developing a control program of LPG losses, a 77% reduction in emission is expected in a 5-yr period. The calculated amounts of LPG emissions when correlated with the consumption of LPG, combined with information from air samples from the MAMC, do not point to LPG emissions as the most important factor contributing to tropospheric ozone in the air in Mexico City.

The environmental agency in the metropolitan area of Mexico City has launched a program to introduce more energy-efficient modes of transport, one of which is the use of alternative and less polluting fuels. With the perspective in mind, a liquefied petroleum gas (LPG) fleet of vehicles is exempt of the mandatory "one day without a car" program if the emission of pollutants is below the standard authorized for that specific purpose. Today, about 28,000 light-duty vehicles and heavy-duty trucks circulate in the area, most of them as aftermarket converted vehicles. In this work, we evaluated regulated exhaust emission and other parameters on 134 representative vehicles of that fleet. From the data obtained, an estimate of emission factors and their contribution to the global emission in the metropolitan area is provided. It is concluded that more than 95% of the in-use vehicles using LPG presented regulated emissions which exceeded in one or more the environmental regulations values required for certification. The poor maintenance of the vehicles and the type of conversion kit installed could be the culprits of the results obtained.

Considering that the prevalence of some hematologic malignancies may have a geographic distribution that could be related with its etiology, a group of 2,387 patients with acute leukemia (1,968 adults and 419 children) was studied along a 5-year period in six different locations within México. Twenty-seven patients (16 males and 11 females) with hairy cell leukemia (HCL) were identified. The adjusted overall proportion of HCL, after excluding data from centers reporting only adults, was 1.12% of all leukemia cases; this figure is lower than that reported in the United States or England. The proportion of adult leukemic patients with HCL was significantly higher in the northern region of the country-where there are more people devoted to farming and agricultural activities-as compared with the central or southeastern regions (3.07 vs. 1.03% vs. 0%; P < 0.05); possible explanations for these differences are briefly discussed.