Forest managers and policy makers increasingly demand to have access to estimates of forest fragmentation, human accessibility to forest areas and levels of anthropogenic pressure on the remaining forests to integrate...Forest managers and policy makers increasingly demand to have access to estimates of forest fragmentation, human accessibility to forest areas and levels of anthropogenic pressure on the remaining forests to integrate them into monitoring systems, management and conservation plans. Forest fragmentation is defined as the breaking up of a forest unit, where the number of patches and the amount of expose edge increase while the amount of core area decreases. Forest fragmentation studies in Mexico have been limited to local or regional levels and have concen- trated only on specific forest types. This paper presents an assessment of the fragmentation of all forest types at the national level, their effective proximity to anthropogenic influences, and the development of an indica- tor of anthropogenic pressure on the forests areas. Broadleaf forests, tropical evergreen forests and tropical dry deciduous forests show the greatest fragmentation. Almost half （47%） of the tropical forests are in close effective proximity to anthropogenic influences and only 12% of their area can be considered isolated from anthropogenic influences. The values for the temperate forests are 23% and 29% respectively. Anthro- pogenic pressure in the immediate vicinity of anthropogenic activities is much higher in the tropical forests （75 in a scale 0-100） than in the tem- perate forests （30）. When considering these results jointly, the tropical forests, and more specifically, the tropical evergreen forests and tropical dry deciduous forests are under the greatest pressure and risks of degra- dation.展开更多
This paper presents assessments of the fragmentation of the temperate and tropical forests in Mexico at the national level for two dates 1993 and 2002.The study was based on land use and vegetation cover data sets sca...This paper presents assessments of the fragmentation of the temperate and tropical forests in Mexico at the national level for two dates 1993 and 2002.The study was based on land use and vegetation cover data sets scale 1：250,000.Two broad forest types（Temperate Forests and Tropical Forests） and five more specific forest types（Broadleaf Forests,and Coniferous Forests;Tropical Dry Deciduous Forests,Tropical Sub-evergreen Forests,and Tropical Evergreen Forests） were defined to conduct the analyses.FragStats 3.3 was used to estimate nine metrics of the spatial pattern of the forests for each forest type and date considered.The results indicate that the land cover transitions that have occurred between 1993 and 2002 have resulted in more isolated forest patches with simpler shapes in both the Temperate and Tropical Forests.The remaining Tropical Forest patches have become smaller and more numerous.In contrast,the remaining Temperate Forest patches are fewer and on average larger.Of the more specific forest types defined in this study,the Broadleaf Forests have the highest indicators of fragmentation.However these forests are usually embedded or adjacent to Coniferous Forests.Of more concern for conservation purposes are the high values of fragmentation metrics found for the Tropical Evergreen Forests and Tropical Dry Deciduous Forests,because these forest types are usually surrounded by non-forest land covers or anthropogenic land uses.展开更多
The largest urban areas of Mexico cities have witnessed high levels of air pollution in the past few decades. The most important air pollutants are ozone and paniculate matter with levels that are still far above curr...The largest urban areas of Mexico cities have witnessed high levels of air pollution in the past few decades. The most important air pollutants are ozone and paniculate matter with levels that are still far above current air quality standard. In this work we studied exhaust and evaporative emissions of Mexico City metropolitan area （MAMC） vehicles using fuels in which sulfur content was varied from 89×10^-6 to 817×10^-6, and calculated the ozone forming potential of emissions as well as the specific reactivity of the exhaust for each average fleet-fuel combinations. Data on emission levels were compared to those obtained in 2000 for the same vintage of vehicles. The almost twofold increase in emissions found could be due to degradation of the exhaust emissions control systems.展开更多
The study of the triacylglycerols (TAG) by gas chromatography (GC) using capillary columns is an efficient technique for the determination of some characteristics of quality of fats and oils. The objective of the pres...The study of the triacylglycerols (TAG) by gas chromatography (GC) using capillary columns is an efficient technique for the determination of some characteristics of quality of fats and oils. The objective of the present study was to determine by GC the content of TAG present in fat of cow and goat milk produced in four zones of Mexico. According to criteria established in Mexican Standardization, 25 samples were obtained of 1 L of ultra-pasteurized cow milk (UHT) and 27 and 48 of raw cow and goat milk, respectively. The fat was extracted from all of the milk samples by detergent solution, and was stored at –20℃ until its analysis. The chromatographic conditions made it possible to identify and quantify TAG of 28 to 54 numbers of carbons, which were analyzed under descriptive and inferential statistical techniques. For the cow milk fat, the statistical analyses indicated significant difference (p < 0.05) in the TAG C34, C50 and C52, and for the goat milk fat in the TAG of C36 to C52. No equality of means was found among the TAG of the cow and goat milk fat. This study offers an advance in the characterization of the TAG present in the cow and goat milk fat produced in Mexico.展开更多
The genus Pterostemon Schauer (Iteaceae), is a group of three species restricted in distribution to Mexico. It includes: Pterostemon mexicanus Schauer, P. rotundifolius Ramírez, and P. bravoanus J. Jiménez-R...The genus Pterostemon Schauer (Iteaceae), is a group of three species restricted in distribution to Mexico. It includes: Pterostemon mexicanus Schauer, P. rotundifolius Ramírez, and P. bravoanus J. Jiménez-Ram. & Martínez Gordillo. On the basis of field observations and herbarium specimens, we review the morphology (vegetative and reproductive), and distribution to give an updated taxonomic treatment for the genus. Additionally the utility of morphological characters is evaluated for taxomic use, and detailed taxonomic descriptions and ecological associations are given for each species.展开更多
Background: Grit is used by birds mainly for grinding hard food items but can also serve a nutritional role as a source of minerals. Ingestion of grit by birds has been documented primarily in species that feed on see...Background: Grit is used by birds mainly for grinding hard food items but can also serve a nutritional role as a source of minerals. Ingestion of grit by birds has been documented primarily in species that feed on seeds and invertebrates.Although feeding mainly on nectar and small arthropods, hummingbirds also ingest grit, but why they do so is unclear. We quantified the number of grit particles in the stomachs of six species of hummingbirds during an annual cycle in a seasonal ecosystem of West Mexico.Methods: We compared the number of grit particles in the stomachs of different hummingbird species(Mexican Violetear Colibri thalassinus, Amethyst-throated Mountaingem Lampornis amethystinus, White-eared Hummingbird Basilinna leucotis, Rivoli's Hummingbird Eugenes fulgens, Broad-tailed Hummingbird Selasphorus platycercus, and Rufous Hummingbird S. rufus), and between sex and age categories during the different seasons of a year. To deter-mine if grit was used to grind ingested arthropods, we examined the relationships between the number of grit parti-cles, the biomass of arthropods ingested, and their chitin content.Results: Although species did not differ in the number of grit particles in their stomachs, we found that grit was mostly ingested by female individuals, with only one male of one species(Mexican Violetear) presenting grit in its stomach. We also found that female hummingbirds had grit in their stomachs during the rainy and the cold-dry season(June-February) but not during the warm-dry season(March-May). Our analyses revealed no relationship between the number of grit particles and the amount of ingested arthropods and arthropod chitin content. However,high grit consumption was related to wasp ingestion on Mexican Violetears.Conclusions: Our results indicate that grit is used mainly by female hummingbirds. The seasonal variation in the ingestion of grit by female individuals suggests that it can be used to meet mineral requirements related to breed-ing;however, this topic needs further exploration. Additionally, the use of grit was proportionally higher in juvenile individuals, suggesting it is used for grinding arthropods during a period of fast development.展开更多
The nature of organochlorine pesticides (OCP) and their physical-chemical properties exert immediate action of control on live systems, which has justified their use in agricultural practices. Their long life makes th...The nature of organochlorine pesticides (OCP) and their physical-chemical properties exert immediate action of control on live systems, which has justified their use in agricultural practices. Their long life makes them a persistent ecological aggressor and biomagnifier. They reach foods by biotic and abiotic means, and are absorbed and accumulate in adipose tissue. In lactation processes, they are excreted in milk through the mobilization of fats. Diverse studies have identified them as neurotoxic, affecting reproductive processes, altering the immunological response and act as endocrine disruptors. An analysis was made of the content of organochlorine pesticides in twenty-one samples of infant milk formulas marketed in the south of Mexico City in 2010. The determinations were made following the protocols of the International Dairy Federation, by means of gas chromatography with electron capture detector, and the majority presence was found of α-HCH (100%), β-HCH (95.2%), γ-HCH (90.5%), aldrin (85.7%), heptachlor (80.9%) and heptachlor epoxide (80.9%) with mean values of 0.24, 0.13, 0.32, 0.62, 0.92 and 0.18 μg/kg of fat, respectively;all below the limits permitted by the Codex Alimentarius. With null or lower recurrence and in lowerquantities, the family of DDT, endrin, endrin aldehyde and the endosulphanes were quantified.展开更多
The Paleozoic flora of the state of Puebla is characterized by the presence of ancient and conservative lineages;we focus this study on the taxonomical Annularia, Bjuvia and the new morphotype. These groups are found ...The Paleozoic flora of the state of Puebla is characterized by the presence of ancient and conservative lineages;we focus this study on the taxonomical Annularia, Bjuvia and the new morphotype. These groups are found in carbonaceous lutite, where paleosoils, small roots and trunks in situ are abundant, and have been associated with swampy environments. In this paper, we discuss the presence of a new architectural form of megaphyll size that has not been registered in other Permian locations. These lutite imprints are the second most abundant in this location and their degree of preservation supports their autochthonous nature. The large size of its funnel-shaped blade and its extremely long petiole support the idea that its size was a response to a competition for biotic resources and to the hydric stress to which communities of this region were exposed, as consequence of the environmental conditions prevailing at the end of the Paleozoic era. It is proposed that they lived in environments with seasonal humidity and this hypothesis is supported by both the abundance of fossil groups and lithology.展开更多
The largest accidental marine oil spill (4.9 million barrels) in the Gulf of Mexico (GoM) seabed (1600 m) caused by the sinking of the Deepwater Horizon oil rig in 2010, put to the test once again the resilient capaci...The largest accidental marine oil spill (4.9 million barrels) in the Gulf of Mexico (GoM) seabed (1600 m) caused by the sinking of the Deepwater Horizon oil rig in 2010, put to the test once again the resilient capacity of the pelagic and benthic realms of this Large Marine Ecosystem. Many are the ecological services provided by its waters (fisheries, tourism, aquaculture and fossil fuel reserves) to neighboring countries (US, Mexico and Cuba). However, the unprecedented volumes of hydrocarbons, gas and chemical dispersants (Corexit) introduced in the system, represent ecological stressors whose deleterious effects are still the subject of civil claims and scientific controversy. Presumably, the short scale effects were confined to the Gulf’s northeastern shallow waters, and the combined actions of weathering, biodegradation, and oil recovery left the system almost under pre-spill conditions. Unfortunately, surface and subsurface oil plumes were detected in the spill aftermath, and their dispersion trajectories threatened Mexico EEZ. Surface oil slicks were detected in the pristine waters of northern Yucatán, while subsurface oil plumes from the Macondo’s well blowout were dangerously advancing southwest towards key fishing grounds in the northwestern GoM. This disaster prompted the Mexican government to implement an ambitious ocean monitoring program adopting a bottom-up approach focused on building a base line for more than 42 physicochemical and biological variables for water, sediment and biota from the continental shelf-slope region of the NW GoM. Technological constraints have precluded systematic observations in the vast Mexican EEZ that could discriminate natural variability and oil seep emissions from antropic disturbances. Therefore, preliminary risk analyses relied on seasonal and historical records. Two years of field observations revealed subtle environmental changes in the studied area attributed to antropic disturbances. Waters maintained oligotrophic conditions and zooplankton and benthic infaunal biomass were also poor. Biomarkers in sediments and biota did not exceed EPA’s benchmarks, and sediment’s fingerprinting (δ13C) indicated marine carbon sources. Geomarkers revealed an active transport from the Mississippi towards the NW GoM of phyllosilicates bearing a weathered oil coating. Consequently, shelf and slope sediment toxicity begins to show an increasing trend in the region. The complexity of hydrocarbons bioaccumulation and biodegradation processes in deep waters of the GoM seems to indicate that meso-and large-scale observations may prove to be essential in understanding the capacity of the GoM to recover its ecological stability.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;"><strong>Objective:</strong> To test the hypothesis that the type 2 diabetes mellitus (T2DM) phenotype in...<div style="text-align:justify;"> <span style="font-family:Verdana;"><strong>Objective:</strong> To test the hypothesis that the type 2 diabetes mellitus (T2DM) phenotype in an indigenous population is characterized by proportionally short legs and obesity. <strong>Methods:</strong> Anthropometric characteristics were compared in females and males with T2DM (n = 20, n = 8, respectively) and without T2DM (n = 117, n = 93, respectively). Factor analysis derived dimensions were regressed on T2DM in logistic regression. <strong>Results:</strong> Weight, sitting height ratio and hip circumference were significantly lower (p < 0.0001) in females, while waist: hip ratio was significantly higher among women and men with T2DM (p < 0.0001 and p < 0.008, respectively). Arm circumference, triceps skinfold, arm muscle circumference, and right and left grip strength were significantly lower among T2DM women (p < 0.0001 for each). Five rotated principal components accounted for 86.7% of the variance: muscular (grip) strength (29.6%), body mass (27.9%), central adiposity (10.7%), body height (9.3%), and trunk length (9.2%). Regression of factors on T2DM status among females indicated muscle strength (OR = 0.16, 95% CI: 0.04 - 0.71) and central adiposity (OR = 13.76, 95% CI: 3.80 - 49.83) were predictors of T2DM. In males, muscle strength (OR = 0.28, 95% CI: 0.07 - 1.08, p < 0.06) and central adiposity significantly predicted T2DM (OR = 3.17, 95% CI: 95% 1.11 - 9.04, p < 0.008). <strong>Conclusion: </strong>Reduced muscle strength/mass and increased central adiposity characterize the T2DM phenotype.</span> </div>展开更多
Guadalajara city is the capital of the Mexican federal state of Jalisco. It is located close to the Pacific coast and is subjected to a large seismic risk. We present a seismic response study for some sites along the ...Guadalajara city is the capital of the Mexican federal state of Jalisco. It is located close to the Pacific coast and is subjected to a large seismic risk. We present a seismic response study for some sites along the city. We calculated response spectra of shear-waves by using seismic records of actual earthquakes registered on rock and near the source as Green functions and propagated them trough a flat and horizontal layered media using a linear equivalent method to compare them with the response spectra calculated according to the Federal Commission of Electricity (CFE) seismic design buildings Manual (MOC-2008, 2008) which is widely used as reference on construction projects in Mexico. Our results show that MOC-2008 manual underestimates the spectral amplitudes and frequency band for the response spectra.展开更多
The incidence of yeast infections has increased significantly over the past few years, constituting a leading cause of morbidity and mortality among hospitalised patients. The rapid identification of candidiasis is im...The incidence of yeast infections has increased significantly over the past few years, constituting a leading cause of morbidity and mortality among hospitalised patients. The rapid identification of candidiasis is important for the clinical management of patients and to facilitate tracing the sources of infections in hospitalized patients. Here, we report a retrospective, single-centre study of Candida spp. distribution and antifungal susceptibility from January 2011 to May 2013 at a hospital in México City, regarding the importance of elucidating the identity of the infection-causing Candida species in order to improve prophylactic measures and treatment. Clinical data were collected from patient medical records and the laboratory database. Isolates were initially identified using standard mycology techniques, and then confirmed by PCR-based system using amplification of intergenic spacers (rDNA ITS) and restriction length polymorphism of PCR products after sequence-specific enzymatic cleavage (PCR-RFLP). We observed no shift from C. albicans to non-albicans Candida species: Candida albicans (73.7%) was the most prevalent species isolated, while C. dubliniensis was not identified in this study. Antifungal susceptibility was determined using FUNGITEST<sup>®</sup>;17.4% of C. albicans isolates were resistant to fluconazole and 21.7% to itraconazole. Multiplex PCR microsatellite analysis of the clinical C. albicans isolates using primers for the CAI, CAIII and CAVI loci identified 29 different alleles for CAI, 8 alleles for CAIII and 31 for CAVI. The combined discriminatory power of these three microsatellites was 0.98, which was considered reliable for molecular typing. Genetic analysis of these isolates revealed a clonal population with a total of 62 genotypes from the examined isolates展开更多
Water quality was evaluated at sites of the Jose Antonio Alzate Dam, the rivers Lerma, Tejalpa and Temoaya in the State of Mexico, Mexico. The variables measured included pH, conductivity, temperature, dissolved oxyge...Water quality was evaluated at sites of the Jose Antonio Alzate Dam, the rivers Lerma, Tejalpa and Temoaya in the State of Mexico, Mexico. The variables measured included pH, conductivity, temperature, dissolved oxygen (DO), ammonia, nitrates, sulfates, sulfides and metal concentrations (Cu and Pb). Chemical speciation for dissolved metals in the aqueous phase was obtained using measured concentrations and the software MINEQL+ (4.5);metal partition coefficients was also obtained using dissolved and particulate concentrations of metals. Hydraulic behavior of the studied water bodies was investigated and the fate of Cu and Pb ions was simulated. The simulation results indicate that the Lerma River provides the majority of organic matter and metal contaminants as a result of a poor oxygen saturation velocity, and showed a slight improvement when the Lerma River is subjected to its tributaries Tejalapa and Temoaya Rivers. Under the reducing conditions predominating along the dam and from the results of aqueous phase chemical speciation, it was found that sulfide metal-associated species are the ones that predominate. It was demonstrated that in general, the rivers Tejalapa and Temoaya presented the best water quality. The Lerma River oxygen saturation improves after the rainy season, but it worsens during the dry season. Due to irregular topography, the small slope prevailing in the Lerma River, and the almost nonexisting water flow, zones with different characteristics are formed within the dam. The sedimentation contributes in the generation of local eddies causing the existence of a small diffusive flow. The order of partition coefficient was Pb > Cu. Cu presented the highest risk levels in the dissolved phase.展开更多
In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006...In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006. Trawling took place from surface to a maximum depth of 200 m, using a Bongo net with a 61 cm mouth diameter and 333 and 500 μm mesh sizes. Temperature and salinity were recorded. Samples were preserved in 4% formalin, neutralized with sodium borate, and changed to 70% ethylic alcohol after 24 hours for conservation. The jellyfish data were standardized to 100 m<sup>3</sup> of filtered water. A total of 10,610 jellyfish were collected from the 333 μm mesh size net, of which eight species represented 88.49% of the total density: Aglaura hemistoma, Liriope tetraphylla, Nausithoe punctata, Clytia hemisphaerica, Persa incolorata, Obelia spp., Clytia folleata and Eutima gracilis. The former three species are the subject of this study. The results obtained indicate that the high density areas of these three species have a segregated distribution. Segregation values (White’s index) recorded between pairs of specie were very high: L. tetraphylla - A. hemistoma, 0.88;L. tetraphylla - N. punctata, 0.86 and A. hemistoma - N. punctata, 0.84. The spatial distribution of the high density areas of these species fits well with the three hydrodynamically different areas: A. hemistoma in Campeche Bank, L. tetraphylla on the Campeche and Tabasco shelves and N. punctata in Campeche Bay. This spatial distribution pattern corresponds to their main habitat and reproductive habits of the species, as well as the influence of the hydrodynamics that dominate each area.展开更多
In this study, the growth of Oreochromis niloticus both mixed sex and males sexually reversed were analyzed in concrete ponds in the FES Zaragoza, UNAM, under the environmental conditions of the Mexico City. The exper...In this study, the growth of Oreochromis niloticus both mixed sex and males sexually reversed were analyzed in concrete ponds in the FES Zaragoza, UNAM, under the environmental conditions of the Mexico City. The experiment was carried from May to November 2013, in two concrete ponds of 50 m2. Similar feeding regime and stocking density of fish were maintained for the culture systems. Different growth parameters like body weight, length, daily weight gain (DWG), specific growth rate (SGR), feed conversion rate (FCR), Fulton’s condition index (K) and survival were analyzed during six months culture period. It was found that culture with monosex males tilapias yielded the highest weight, length, DWG and SGR compared to mixed sex populations tilapias. Water quality was monitored along the experiment. Based on the results, there were statistically significant differences in size (W = 20942.5, p 5 mg/L), warm water (>20°C), productive (3) and slightly basic (pH > 8). Acceptable growth of fish and a yield of 3 ton/ha/6 months were obtained in both two ponds;therefore, the culture of tilapia under conditions of Mexico City was recommended.展开更多
Slaughtered cattle (n = 582) from México State were bled for a serological screening of clenbuterol residues, using a commercial enzyme-linked immunosorbent assay (ELISA). Clenbuterol residues were found in a tot...Slaughtered cattle (n = 582) from México State were bled for a serological screening of clenbuterol residues, using a commercial enzyme-linked immunosorbent assay (ELISA). Clenbuterol residues were found in a total of 153/582 (26.2%) sera analysed. These results reinforced the assumption of the illegal use of clenbuterol in cattle production in México;therefore, routine screening examinations in slaughtered cattle were strongly advised considering the toxic potential for humans.展开更多
Crohn's disease(CD)and ulcerative colitis(UC)are complex polygenic disorders,characterized by several genes together with environmental factors contributing to the development of inflammatory bowel disease(IBD).Re...Crohn's disease(CD)and ulcerative colitis(UC)are complex polygenic disorders,characterized by several genes together with environmental factors contributing to the development of inflammatory bowel disease(IBD).Recent advances in research on genetic susceptibility have allowed the identification of diverse genes at different levels:(1)Innate immunity;(2)Antigen presentation molecules;(3)Epithelial integrity;(4)Drug transporter;(5)Cell adhesion.The application of genetic testing into clinical practice is close and all genetic markers may have several clinical implications:prediction of disease phenotype,molecular classification,prevention of complications,and prognosis.展开更多
文摘Forest managers and policy makers increasingly demand to have access to estimates of forest fragmentation, human accessibility to forest areas and levels of anthropogenic pressure on the remaining forests to integrate them into monitoring systems, management and conservation plans. Forest fragmentation is defined as the breaking up of a forest unit, where the number of patches and the amount of expose edge increase while the amount of core area decreases. Forest fragmentation studies in Mexico have been limited to local or regional levels and have concen- trated only on specific forest types. This paper presents an assessment of the fragmentation of all forest types at the national level, their effective proximity to anthropogenic influences, and the development of an indica- tor of anthropogenic pressure on the forests areas. Broadleaf forests, tropical evergreen forests and tropical dry deciduous forests show the greatest fragmentation. Almost half （47%） of the tropical forests are in close effective proximity to anthropogenic influences and only 12% of their area can be considered isolated from anthropogenic influences. The values for the temperate forests are 23% and 29% respectively. Anthro- pogenic pressure in the immediate vicinity of anthropogenic activities is much higher in the tropical forests （75 in a scale 0-100） than in the tem- perate forests （30）. When considering these results jointly, the tropical forests, and more specifically, the tropical evergreen forests and tropical dry deciduous forests are under the greatest pressure and risks of degra- dation.
文摘This paper presents assessments of the fragmentation of the temperate and tropical forests in Mexico at the national level for two dates 1993 and 2002.The study was based on land use and vegetation cover data sets scale 1：250,000.Two broad forest types（Temperate Forests and Tropical Forests） and five more specific forest types（Broadleaf Forests,and Coniferous Forests;Tropical Dry Deciduous Forests,Tropical Sub-evergreen Forests,and Tropical Evergreen Forests） were defined to conduct the analyses.FragStats 3.3 was used to estimate nine metrics of the spatial pattern of the forests for each forest type and date considered.The results indicate that the land cover transitions that have occurred between 1993 and 2002 have resulted in more isolated forest patches with simpler shapes in both the Temperate and Tropical Forests.The remaining Tropical Forest patches have become smaller and more numerous.In contrast,the remaining Temperate Forest patches are fewer and on average larger.Of the more specific forest types defined in this study,the Broadleaf Forests have the highest indicators of fragmentation.However these forests are usually embedded or adjacent to Coniferous Forests.Of more concern for conservation purposes are the high values of fragmentation metrics found for the Tropical Evergreen Forests and Tropical Dry Deciduous Forests,because these forest types are usually surrounded by non-forest land covers or anthropogenic land uses.
文摘The largest urban areas of Mexico cities have witnessed high levels of air pollution in the past few decades. The most important air pollutants are ozone and paniculate matter with levels that are still far above current air quality standard. In this work we studied exhaust and evaporative emissions of Mexico City metropolitan area （MAMC） vehicles using fuels in which sulfur content was varied from 89×10^-6 to 817×10^-6, and calculated the ozone forming potential of emissions as well as the specific reactivity of the exhaust for each average fleet-fuel combinations. Data on emission levels were compared to those obtained in 2000 for the same vintage of vehicles. The almost twofold increase in emissions found could be due to degradation of the exhaust emissions control systems.
文摘The study of the triacylglycerols (TAG) by gas chromatography (GC) using capillary columns is an efficient technique for the determination of some characteristics of quality of fats and oils. The objective of the present study was to determine by GC the content of TAG present in fat of cow and goat milk produced in four zones of Mexico. According to criteria established in Mexican Standardization, 25 samples were obtained of 1 L of ultra-pasteurized cow milk (UHT) and 27 and 48 of raw cow and goat milk, respectively. The fat was extracted from all of the milk samples by detergent solution, and was stored at –20℃ until its analysis. The chromatographic conditions made it possible to identify and quantify TAG of 28 to 54 numbers of carbons, which were analyzed under descriptive and inferential statistical techniques. For the cow milk fat, the statistical analyses indicated significant difference (p < 0.05) in the TAG C34, C50 and C52, and for the goat milk fat in the TAG of C36 to C52. No equality of means was found among the TAG of the cow and goat milk fat. This study offers an advance in the characterization of the TAG present in the cow and goat milk fat produced in Mexico.
文摘The genus Pterostemon Schauer (Iteaceae), is a group of three species restricted in distribution to Mexico. It includes: Pterostemon mexicanus Schauer, P. rotundifolius Ramírez, and P. bravoanus J. Jiménez-Ram. & Martínez Gordillo. On the basis of field observations and herbarium specimens, we review the morphology (vegetative and reproductive), and distribution to give an updated taxonomic treatment for the genus. Additionally the utility of morphological characters is evaluated for taxomic use, and detailed taxonomic descriptions and ecological associations are given for each species.
文摘Background: Grit is used by birds mainly for grinding hard food items but can also serve a nutritional role as a source of minerals. Ingestion of grit by birds has been documented primarily in species that feed on seeds and invertebrates.Although feeding mainly on nectar and small arthropods, hummingbirds also ingest grit, but why they do so is unclear. We quantified the number of grit particles in the stomachs of six species of hummingbirds during an annual cycle in a seasonal ecosystem of West Mexico.Methods: We compared the number of grit particles in the stomachs of different hummingbird species(Mexican Violetear Colibri thalassinus, Amethyst-throated Mountaingem Lampornis amethystinus, White-eared Hummingbird Basilinna leucotis, Rivoli's Hummingbird Eugenes fulgens, Broad-tailed Hummingbird Selasphorus platycercus, and Rufous Hummingbird S. rufus), and between sex and age categories during the different seasons of a year. To deter-mine if grit was used to grind ingested arthropods, we examined the relationships between the number of grit parti-cles, the biomass of arthropods ingested, and their chitin content.Results: Although species did not differ in the number of grit particles in their stomachs, we found that grit was mostly ingested by female individuals, with only one male of one species(Mexican Violetear) presenting grit in its stomach. We also found that female hummingbirds had grit in their stomachs during the rainy and the cold-dry season(June-February) but not during the warm-dry season(March-May). Our analyses revealed no relationship between the number of grit particles and the amount of ingested arthropods and arthropod chitin content. However,high grit consumption was related to wasp ingestion on Mexican Violetears.Conclusions: Our results indicate that grit is used mainly by female hummingbirds. The seasonal variation in the ingestion of grit by female individuals suggests that it can be used to meet mineral requirements related to breed-ing;however, this topic needs further exploration. Additionally, the use of grit was proportionally higher in juvenile individuals, suggesting it is used for grinding arthropods during a period of fast development.
文摘The nature of organochlorine pesticides (OCP) and their physical-chemical properties exert immediate action of control on live systems, which has justified their use in agricultural practices. Their long life makes them a persistent ecological aggressor and biomagnifier. They reach foods by biotic and abiotic means, and are absorbed and accumulate in adipose tissue. In lactation processes, they are excreted in milk through the mobilization of fats. Diverse studies have identified them as neurotoxic, affecting reproductive processes, altering the immunological response and act as endocrine disruptors. An analysis was made of the content of organochlorine pesticides in twenty-one samples of infant milk formulas marketed in the south of Mexico City in 2010. The determinations were made following the protocols of the International Dairy Federation, by means of gas chromatography with electron capture detector, and the majority presence was found of α-HCH (100%), β-HCH (95.2%), γ-HCH (90.5%), aldrin (85.7%), heptachlor (80.9%) and heptachlor epoxide (80.9%) with mean values of 0.24, 0.13, 0.32, 0.62, 0.92 and 0.18 μg/kg of fat, respectively;all below the limits permitted by the Codex Alimentarius. With null or lower recurrence and in lowerquantities, the family of DDT, endrin, endrin aldehyde and the endosulphanes were quantified.
文摘The Paleozoic flora of the state of Puebla is characterized by the presence of ancient and conservative lineages;we focus this study on the taxonomical Annularia, Bjuvia and the new morphotype. These groups are found in carbonaceous lutite, where paleosoils, small roots and trunks in situ are abundant, and have been associated with swampy environments. In this paper, we discuss the presence of a new architectural form of megaphyll size that has not been registered in other Permian locations. These lutite imprints are the second most abundant in this location and their degree of preservation supports their autochthonous nature. The large size of its funnel-shaped blade and its extremely long petiole support the idea that its size was a response to a competition for biotic resources and to the hydric stress to which communities of this region were exposed, as consequence of the environmental conditions prevailing at the end of the Paleozoic era. It is proposed that they lived in environments with seasonal humidity and this hypothesis is supported by both the abundance of fossil groups and lithology.
文摘The largest accidental marine oil spill (4.9 million barrels) in the Gulf of Mexico (GoM) seabed (1600 m) caused by the sinking of the Deepwater Horizon oil rig in 2010, put to the test once again the resilient capacity of the pelagic and benthic realms of this Large Marine Ecosystem. Many are the ecological services provided by its waters (fisheries, tourism, aquaculture and fossil fuel reserves) to neighboring countries (US, Mexico and Cuba). However, the unprecedented volumes of hydrocarbons, gas and chemical dispersants (Corexit) introduced in the system, represent ecological stressors whose deleterious effects are still the subject of civil claims and scientific controversy. Presumably, the short scale effects were confined to the Gulf’s northeastern shallow waters, and the combined actions of weathering, biodegradation, and oil recovery left the system almost under pre-spill conditions. Unfortunately, surface and subsurface oil plumes were detected in the spill aftermath, and their dispersion trajectories threatened Mexico EEZ. Surface oil slicks were detected in the pristine waters of northern Yucatán, while subsurface oil plumes from the Macondo’s well blowout were dangerously advancing southwest towards key fishing grounds in the northwestern GoM. This disaster prompted the Mexican government to implement an ambitious ocean monitoring program adopting a bottom-up approach focused on building a base line for more than 42 physicochemical and biological variables for water, sediment and biota from the continental shelf-slope region of the NW GoM. Technological constraints have precluded systematic observations in the vast Mexican EEZ that could discriminate natural variability and oil seep emissions from antropic disturbances. Therefore, preliminary risk analyses relied on seasonal and historical records. Two years of field observations revealed subtle environmental changes in the studied area attributed to antropic disturbances. Waters maintained oligotrophic conditions and zooplankton and benthic infaunal biomass were also poor. Biomarkers in sediments and biota did not exceed EPA’s benchmarks, and sediment’s fingerprinting (δ13C) indicated marine carbon sources. Geomarkers revealed an active transport from the Mississippi towards the NW GoM of phyllosilicates bearing a weathered oil coating. Consequently, shelf and slope sediment toxicity begins to show an increasing trend in the region. The complexity of hydrocarbons bioaccumulation and biodegradation processes in deep waters of the GoM seems to indicate that meso-and large-scale observations may prove to be essential in understanding the capacity of the GoM to recover its ecological stability.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;"><strong>Objective:</strong> To test the hypothesis that the type 2 diabetes mellitus (T2DM) phenotype in an indigenous population is characterized by proportionally short legs and obesity. <strong>Methods:</strong> Anthropometric characteristics were compared in females and males with T2DM (n = 20, n = 8, respectively) and without T2DM (n = 117, n = 93, respectively). Factor analysis derived dimensions were regressed on T2DM in logistic regression. <strong>Results:</strong> Weight, sitting height ratio and hip circumference were significantly lower (p < 0.0001) in females, while waist: hip ratio was significantly higher among women and men with T2DM (p < 0.0001 and p < 0.008, respectively). Arm circumference, triceps skinfold, arm muscle circumference, and right and left grip strength were significantly lower among T2DM women (p < 0.0001 for each). Five rotated principal components accounted for 86.7% of the variance: muscular (grip) strength (29.6%), body mass (27.9%), central adiposity (10.7%), body height (9.3%), and trunk length (9.2%). Regression of factors on T2DM status among females indicated muscle strength (OR = 0.16, 95% CI: 0.04 - 0.71) and central adiposity (OR = 13.76, 95% CI: 3.80 - 49.83) were predictors of T2DM. In males, muscle strength (OR = 0.28, 95% CI: 0.07 - 1.08, p < 0.06) and central adiposity significantly predicted T2DM (OR = 3.17, 95% CI: 95% 1.11 - 9.04, p < 0.008). <strong>Conclusion: </strong>Reduced muscle strength/mass and increased central adiposity characterize the T2DM phenotype.</span> </div>
文摘Guadalajara city is the capital of the Mexican federal state of Jalisco. It is located close to the Pacific coast and is subjected to a large seismic risk. We present a seismic response study for some sites along the city. We calculated response spectra of shear-waves by using seismic records of actual earthquakes registered on rock and near the source as Green functions and propagated them trough a flat and horizontal layered media using a linear equivalent method to compare them with the response spectra calculated according to the Federal Commission of Electricity (CFE) seismic design buildings Manual (MOC-2008, 2008) which is widely used as reference on construction projects in Mexico. Our results show that MOC-2008 manual underestimates the spectral amplitudes and frequency band for the response spectra.
文摘The incidence of yeast infections has increased significantly over the past few years, constituting a leading cause of morbidity and mortality among hospitalised patients. The rapid identification of candidiasis is important for the clinical management of patients and to facilitate tracing the sources of infections in hospitalized patients. Here, we report a retrospective, single-centre study of Candida spp. distribution and antifungal susceptibility from January 2011 to May 2013 at a hospital in México City, regarding the importance of elucidating the identity of the infection-causing Candida species in order to improve prophylactic measures and treatment. Clinical data were collected from patient medical records and the laboratory database. Isolates were initially identified using standard mycology techniques, and then confirmed by PCR-based system using amplification of intergenic spacers (rDNA ITS) and restriction length polymorphism of PCR products after sequence-specific enzymatic cleavage (PCR-RFLP). We observed no shift from C. albicans to non-albicans Candida species: Candida albicans (73.7%) was the most prevalent species isolated, while C. dubliniensis was not identified in this study. Antifungal susceptibility was determined using FUNGITEST<sup>®</sup>;17.4% of C. albicans isolates were resistant to fluconazole and 21.7% to itraconazole. Multiplex PCR microsatellite analysis of the clinical C. albicans isolates using primers for the CAI, CAIII and CAVI loci identified 29 different alleles for CAI, 8 alleles for CAIII and 31 for CAVI. The combined discriminatory power of these three microsatellites was 0.98, which was considered reliable for molecular typing. Genetic analysis of these isolates revealed a clonal population with a total of 62 genotypes from the examined isolates
文摘Water quality was evaluated at sites of the Jose Antonio Alzate Dam, the rivers Lerma, Tejalpa and Temoaya in the State of Mexico, Mexico. The variables measured included pH, conductivity, temperature, dissolved oxygen (DO), ammonia, nitrates, sulfates, sulfides and metal concentrations (Cu and Pb). Chemical speciation for dissolved metals in the aqueous phase was obtained using measured concentrations and the software MINEQL+ (4.5);metal partition coefficients was also obtained using dissolved and particulate concentrations of metals. Hydraulic behavior of the studied water bodies was investigated and the fate of Cu and Pb ions was simulated. The simulation results indicate that the Lerma River provides the majority of organic matter and metal contaminants as a result of a poor oxygen saturation velocity, and showed a slight improvement when the Lerma River is subjected to its tributaries Tejalapa and Temoaya Rivers. Under the reducing conditions predominating along the dam and from the results of aqueous phase chemical speciation, it was found that sulfide metal-associated species are the ones that predominate. It was demonstrated that in general, the rivers Tejalapa and Temoaya presented the best water quality. The Lerma River oxygen saturation improves after the rainy season, but it worsens during the dry season. Due to irregular topography, the small slope prevailing in the Lerma River, and the almost nonexisting water flow, zones with different characteristics are formed within the dam. The sedimentation contributes in the generation of local eddies causing the existence of a small diffusive flow. The order of partition coefficient was Pb > Cu. Cu presented the highest risk levels in the dissolved phase.
文摘In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006. Trawling took place from surface to a maximum depth of 200 m, using a Bongo net with a 61 cm mouth diameter and 333 and 500 μm mesh sizes. Temperature and salinity were recorded. Samples were preserved in 4% formalin, neutralized with sodium borate, and changed to 70% ethylic alcohol after 24 hours for conservation. The jellyfish data were standardized to 100 m<sup>3</sup> of filtered water. A total of 10,610 jellyfish were collected from the 333 μm mesh size net, of which eight species represented 88.49% of the total density: Aglaura hemistoma, Liriope tetraphylla, Nausithoe punctata, Clytia hemisphaerica, Persa incolorata, Obelia spp., Clytia folleata and Eutima gracilis. The former three species are the subject of this study. The results obtained indicate that the high density areas of these three species have a segregated distribution. Segregation values (White’s index) recorded between pairs of specie were very high: L. tetraphylla - A. hemistoma, 0.88;L. tetraphylla - N. punctata, 0.86 and A. hemistoma - N. punctata, 0.84. The spatial distribution of the high density areas of these species fits well with the three hydrodynamically different areas: A. hemistoma in Campeche Bank, L. tetraphylla on the Campeche and Tabasco shelves and N. punctata in Campeche Bay. This spatial distribution pattern corresponds to their main habitat and reproductive habits of the species, as well as the influence of the hydrodynamics that dominate each area.
基金supported by the Facultad de Estudios Superiores Zaragoza and DGAPA-PAPIME program(project code PE205513)of National Autonomous University of México.
文摘In this study, the growth of Oreochromis niloticus both mixed sex and males sexually reversed were analyzed in concrete ponds in the FES Zaragoza, UNAM, under the environmental conditions of the Mexico City. The experiment was carried from May to November 2013, in two concrete ponds of 50 m2. Similar feeding regime and stocking density of fish were maintained for the culture systems. Different growth parameters like body weight, length, daily weight gain (DWG), specific growth rate (SGR), feed conversion rate (FCR), Fulton’s condition index (K) and survival were analyzed during six months culture period. It was found that culture with monosex males tilapias yielded the highest weight, length, DWG and SGR compared to mixed sex populations tilapias. Water quality was monitored along the experiment. Based on the results, there were statistically significant differences in size (W = 20942.5, p 5 mg/L), warm water (>20°C), productive (3) and slightly basic (pH > 8). Acceptable growth of fish and a yield of 3 ton/ha/6 months were obtained in both two ponds;therefore, the culture of tilapia under conditions of Mexico City was recommended.
文摘Slaughtered cattle (n = 582) from México State were bled for a serological screening of clenbuterol residues, using a commercial enzyme-linked immunosorbent assay (ELISA). Clenbuterol residues were found in a total of 153/582 (26.2%) sera analysed. These results reinforced the assumption of the illegal use of clenbuterol in cattle production in México;therefore, routine screening examinations in slaughtered cattle were strongly advised considering the toxic potential for humans.
文摘Crohn's disease(CD)and ulcerative colitis(UC)are complex polygenic disorders,characterized by several genes together with environmental factors contributing to the development of inflammatory bowel disease(IBD).Recent advances in research on genetic susceptibility have allowed the identification of diverse genes at different levels:(1)Innate immunity;(2)Antigen presentation molecules;(3)Epithelial integrity;(4)Drug transporter;(5)Cell adhesion.The application of genetic testing into clinical practice is close and all genetic markers may have several clinical implications:prediction of disease phenotype,molecular classification,prevention of complications,and prognosis.
