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This research presents an updated scheme of simulation for strong ground motions based on stochastic summation methods and the source-to-site attenuation effects under particular soil conditions different from firm sites. Two approaches are proposed to modify and improve the empirical Green's functions at different source distances from seismic station records: (1) a spectral shape based on far-field point-source spectra models and (2) through specific ground motion prediction equations (GMPEs) and random vibration theory (RVT). The ground motions simulated were compared with the September 19, 2017 Mexico records (normal-fault-intraslab event, Mw 7.1), finding that for soft soils, it will be possible to reproduce some characteristic of spectral peaks appropriately in high frequency compared with available similar approaches or using one-dimensional wave propagation models. On average, the spectral overestimations from available simulation approaches and for high-frequency bandwidth (i.e., 0.2 s and 0.3 s) can be reduced by a factor between 2 and 5 using proper attenuation corrections; this effect could be especially beneficial for small structures and low-rise buildings where the inertial design forces will be potentially reduced. [ABSTRACT FROM AUTHOR]

The eastern oyster ( Crassostrea virginica Gmelin) is an economically and ecologically valuable marine bivalve occurring in the Gulf of Mexico. This study builds upon previous research that identified two divergent populations of eastern oysters in the western Gulf of Mexico. Allelic and genotypic patterns from 11 microsatellite markers were used to assess genetic structure and migration between the previously described oyster populations in Texas. The main findings are as follows: (1) there are two distinct populations ( FST = 0.392, P < 0.001) of oysters that overlap in the Corpus Christi/Aransas Bay estuarine complex in Texas, (2) the distribution of genotypes among individuals in the contact zone suggests limited hybridization between populations, (3) the variables of salinity, temperature, dissolved oxygen, turbidity and depth are not correlated with allele frequencies on reefs in the contact zone or when analyzed across Texas, and (4) there is little evidence of directional selection acting on the loci assayed here, although patterns at four markers suggested the influence of balancing selection based on outlier analyses. These results are consistent with long-term historical isolation between populations, followed by secondary contact. Recent hydrological changes in the area of secondary contact may be promoting migration in areas that were previously inhospitable to eastern oysters, and observed differences in the timing of spawning may limit hybridization between populations. Comparison of these findings with the results of an earlier study of oysters in Texas suggests that the secondary contact zone has shifted approximately 27 km north, in as little as a 23-year span. [ABSTRACT FROM AUTHOR]

Abstract: Climate change will affect agricultural production by subsistence farms in crop centers of origin, where landraces are conserved in situ. Various strategies for adaptation to climate change have been proposed. In this paper we examine the prospects of what we call the ‘transgenic adaptation strategy’, i.e. the appeal to use transgenic seeds to adapt to climate change, through the lens of smallholder maize farming in Mexico. Landraces are the bedrock of maize production in Mexico. We consider how maize farmers may respond to climate change and the effects of those responses on crop diversity. In this paper, we argue that the promotion of the transgenic adaptation strategy is problematic for biological and social reasons. Smallholder livelihoods in southern Mexico could suffer a disproportionate negative impact if transgenic technology is privileged as a response to climate change. Agroecological and evolutionary approaches to addressing the effects of climate change on smallholder agriculture provides an alternative adaptive strategy. [Copyright &y& Elsevier]

Strategies for conservation and management of marine species are increasingly relying on molecular genetic data for the delineation of independent fishery stocks. These data may be more reliable and less subjective than morphological or ecological variables, although their biological interpretations can be problematic. Here, we review existing morphological data synergistically with a new molecular data set for sheepsheads Archosargus probatocephalus. Two named subspecies of sheepshead exist in the northeastern Gulf of Mexico (A. probatocephalus probatocephalus and A. probatocephalus oviceps). Although these subspecies exhibit divergent morphology, it is unclear whether morphological divergence represents meaningful differentiation for management. We show that frequency distributions of each of five meristic counts are significantly different between the subspecies (P < 0.05). However, Bayesian structure analysis of microsatellite genotypes indicated that all Gulf of Mexico sheepshead populations constitute a single stock (posterior probability ≈ 0.9999). Variance partitioning of mitochondrial DNA (mtDNA) haplotypes suggests significant but limited divergence between subspecies (genetic differentiation index FST = 0.036, P < 0.005). Patterns of pairwise mtDNA genetic distance and microsatellite divergence suggest that isolation by distance, rather than subdivision among independent genetic stocks, is driving the significance of variance analyses. Overall, sheepshead molecular genetic data indicate very limited genetic subdivision between the subspecies despite considerable divergence of morphological characters. These results have multiple interpretations, each of which carries implications for the management of this species in the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

A highly publicized study in 2001 reported that maize landraces in Oaxaca, Mexico were found to contain transgenes, yet not all follow-up research has detected transgenes in the same region. Continued testing for transgenes in Mexican maize, and calls for the removal of transgenes from landraces, have only fueled the debate about the dynamics of gene flow from transgenic maize to landraces in Mexico. This paper reviews these recent findings and discusses how evolution may be expected to alter the frequency of transgenes in crop populations over time. Further, it shows that calls for removing transgenes must be interpreted in light of two ecological complexities: (a) it may be impossible to purge a particular gene from a population and (b) scientists’ ability to accurately determine the presence or absence of transgenes is limited by challenges related to sampling. The paper concludes by outlining two ways forward for removing transgenes from landraces. [Copyright &y& Elsevier]

This article examines attitudes of Mexican and U.S. managers regarding the potential impact of the North American Free Trade Agreement. Attitudes about overall economic impact, industrial competitiveness, products and markets, technology, employment, tariffs and trade, the environment, and political issues are assessed. Conclusions and suggestions for future research are discussed. [ABSTRACT FROM AUTHOR]

The following study investigates the relative roles of quality perceptions and customer satisfaction judgements in the formation of the purchase intentions of Mexican consumers. Data for the study included three hundred and sixty five surveys of adult Mexican consumers that were captured using mall intercepts in a large city in central Mexico. The results suggest that (1) satisfaction judgements appear to contribute more to purchase intentions, and (2) the nature of the relationship between the satisfaction and quality constructs in this process appears largely additive rather than interactive -- contrary to findings recently reported with consumers of the United States. [ABSTRACT FROM AUTHOR]

Background: Respiratory diseases are a major component of morbidity in children and their symptoms may be spatially and temporally exacerbated by exposure gradients of fine particulate matter (PM 2.5 ) in large polluted urban areas, like the Mexico City Metropolitan Area (MCMA)., Objectives: To analyze the association between satellite-derived and interpolated PM 2.5 estimates with children's (≤9 years old) acute respiratory symptoms (ARS) in two probabilistic samples representing the MCMA., Methods: We obtained ARS data from the 2006 and 2012 National Surveys for Health and Nutrition (ENSaNut). Two week average exposure to PM 2.5 was assessed for each household with spatial estimates from a hybrid model with satellite measurements of aerosol optical depth (AOD-PM 2.5 ) and also with interpolated PM 2.5 measurements from ground stations, from the Mexico City monitoring network (MNW-PM 2.5 ). We used survey-adjusted logistic regressions to analyze the association between PM 2.5 estimates and ARS reported on children., Results: A total of 1,005 and 1,233 children were surveyed in 2006 and 2012 representing 3.1 and 3.5 million children, respectively. For the same years and over the periods of study, the estimated prevalence of ARS decreased from 49.4% (95% CI: 44.9,53.9%) to 37.8% (95% CI: 34,41.7%). AOD-PM 2.5 and MNW-PM 2.5 estimates were associated with significantly higher reports of ARS in children 0-4 years old [OR 2006  = 1.29 (95% (CI): 0.99,1.68) and OR 2006  = 1.24 (95% CI: 1.08,1.42), respectively]. We observed positive non-significant associations in 2012 in both age groups and in 2006 for children 5-9 years old. No statistically significant differences in health effect estimates of PM 2.5 were found comparing AOD-PM 2.5 or MNW-PM 2.5 for exposure assessment., Conclusions: Our findings suggest that PM 2.5 is a risk factor for the prevalence of ARS in children and expand the growing evidence of the utility of new satellite AOD-based methods for estimating health effects from acute exposure to PM 2.5 ., (Copyright © 2019 Elsevier Inc. All rights reserved.)

We combined N, C, and Hg stable isotope measurements to identify the most important factors that influence MeHg accumulation in fish from the northern Gulf of Mexico (nGOM), and to determine if coastal species residing in the Mississippi River (MR) plume and migratory oceanic species derive their MeHg from the same, or different, sources. In six coastal species and two oceanic species (blackfin and yellowfin tuna), trophic position as measured by delta(15)N explained most of the variance in log[MeHg] (r(2) approximately 0.8), but coastal species and tuna fell along distinct, nearly parallel lines with significantly different intercepts. The tuna also had significantly higher delta(202)Hg (0.2-0.5 per thousand) and Delta(201)Hg ( approximately 1.5 per thousand) than the coastal fish (delta(202)Hg = 0 to -1.0 per thousand; Delta(201)Hg approximately 0.4 per thousand). The observations can be best explained by largely disconnected food webs rooted in different baseline delta(15)N signatures (MR-plume vs oceanic) and isotopically distinct MeHg sources, with oceanic MeHg having undergone substantial photodegradation ( approximately 50%) before entering the base of the food web. Given the MR's large, productive footprint in the nGOM and the potential for exporting prey and MeHg to the adjacent oligotrophic GOM, the disconnected food webs and different MeHg sources are consistent with recent evidence in other systems of important oceanic MeHg sources.

Latino families who express a higher degree of familism are characterized by positive interpersonal familial relationships, high family unity, social support, interdependence in the completion of daily activities, and close proximity with extended family members. Retention of cultural values, such as familism, may be linked to positive health outcomes; however, little is known about how families retain culture of origin values in the face of acculturation pressures. The current study explores acculturation influences as indexed by language preference and household education on maternal and child familism. Mothers and children of Mexican descent (fourth grade students) (n = 219) completed measures of demographics, household education, language preference, and familism. Three hypotheses were examined. First, we predicted that lower household education would be correlated with higher familism scores. However, contrary to our prediction, a higher familism score was significantly associated with a higher level of household education (p <.05). Second, we predicted that higher child familism would be associated with the preference for speaking Spanish. Children who preferred to use both English and Spanish (p <.01) or English alone (p <.05) had higher familism scores than those who preferred Spanish. Third, we predicted that lower child familism scores would be associated with greater differences in mother and child language preferences. There were no significant differences in child familism based on differences between parent and child language. Protective influences of cultural maintenance deserve further attention in longitudinal studies and in relation to the physical and mental health of youth.