Underlying and proximate drivers of biodiversity changes in Mesoamerican biosphere reserves.

Protected areas are of paramount relevance to conserving wildlife and ecosystem contributions to people. Yet, their conservation success is increasingly threatened by human activities including habitat loss, climate change, pollution, and species overexploitation. Thus, understanding the underlying and proximate drivers of anthropogenic threats is urgently needed to improve protected areas' effectiveness, especially in the biodiversity-rich tropics. We addressed this issue by analyzing expert-provided data on long-term biodiversity change (last three decades) over 14 biosphere reserves from the Mesoamerican Biodiversity Hotspot. Using multivariate analyses and structural equation modeling, we tested the influence of major socioeconomic drivers (demographic, economic, and political factors), spatial indicators of human activities (agriculture expansion and road extension), and forest landscape modifications (forest loss and isolation) as drivers of biodiversity change. We uncovered a significant proliferation of disturbance-tolerant guilds and the loss or decline of disturbance-sensitive guilds within reserves causing a "winner and loser" species replacement over time. Guild change was directly related to forest spatial changes promoted by the expansion of agriculture and roads within reserves. High human population density and low nonfarming occupation were identified as the main underlying drivers of biodiversity change. Our findings suggest that to mitigate anthropogenic threats to biodiversity within biosphere reserves, fostering human population well-being via sustainable, nonfarming livelihood opportunities around reserves is imperative.

How diverse are the mountain karst forests of Mexico?

Tropical forests on karstic relief (tropical karst forest) are among the most species-rich biomes. These forests play pivotal roles as global climate regulators and for human wellbeing. Their long-term conservation could be central to global climate mitigation and biodiversity conservation. In Mexico, karst landscapes occupy 20% of the total land surface and are distributed mainly in the southeast of the country, along the eastern slope, and in the Yucatan Peninsula. Within each of these areas, the following types of karst occur: coastal karst, plain karst, hill karst, and mountain karst (low, medium, high). Mountain karst cover 2.07% of Mexico's land surface and are covered by tropical rainforests, montane cloud forests, and tropical deciduous forests. These are probably one of the most diverse biomes in Mexico. However, the mountain karst forests of Mexico have received little attention, and very little is known about their diversity. Here, we evaluated the vascular plant species richness within the mountain karst forests of Mexico. We assembled the first, largest, and most comprehensive datasets of Mexican mountain karst forest species, from different public databases (CONABIO, GBIF, IBdata-UNAM), which included a critical review of all data. We compiled a list of the families, genera, and species present within the mountain karst forests of Mexico. Taxa that best characterize these forests were identified based on their spatial correlation with this biome. We explored biodiversity patterns, identifying areas with the highest species richness, endemism centers, and areas of relatively low sampling intensity. We found that within the mountain karst forests of Mexico there are representatives of 11,771 vascular plant species (253 families and 2,254 genera), ca. 50% of the Mexican flora. We identified 372 species endemic to these forests. According to preliminary IUCN red list criteria, 2,477 species are under some category of conservation risk, of which 456 (3.8%) are endangered. Most of the Mexican mountain karst forests have been extensively explored and six allopatric, species-rich areas were identified. Compared to other regions in the world, the mountain karst forests of Mexico are one of the most diverse biomes. They contain more species than some entire montane systems in Mexico such as Sierra Madre Oriental, and Sierra Madre del Sur. Also, the mountain karst forests of Mexico are most diverse than similar forests of South America and Asia, even if considering the effect of different sampling areas. The fact that mountain karst forests are embedded in areas of high biotic diversity, probably contributes to their great floristic diversity. Thus, the mountain karst forests of Mexico are an important source of diversity and shelters a large percentage of the Mexican flora.

Variación Morfológica en la Musculatura Cefálica de Diplobatis ommata y Narcine vermiculatus (Chondrychthyes: Narcinidae) / Morphological Variation in the Cephalic Musculature of Diplobatis ommata and Narcine vermiculatus (Chondrychthyes: Narcinidae)

Los trabajos realizados sobre batoideos han demostrado que existen grandes variaciones en la musculatura de la región cefálica ventral, estos cambios están asociados a los diferentes estilos de vida de los organismos y por tanto, a los mecanismos de alimentación. El objetivo de este trabajo fue llevar a cabo un estudio comparativo de la morfología de la musculatura cefálica dorsal y ventral de dos especies de la familia Narcinidae: Narcine vermiculatus y Diplobatis ommata. Se observó que ambas especies comparten un patrón morfológico común. Los músculos que mostraron mayores variaciones en la región dorsal fueron el depresor rostral, el preorbital lateral y el elevador rostral. La diferencia más importante en esta región, entre ambas especies, fue la ausencia del músculo cucularis en D. ommata. En la región ventral las principales diferencias se observaron en los músculos depresor mandibular, preorbital medial, interbranquial y depresor hiomandibular. Este último músculo está formado por dos paquetes en D. ommata, en tanto que en N. vermiculatus por uno. Se puede concluir que la morfología de la musculatura cefálica es constante; sin embargo, se observan diferencias importantes en el grado de desarrollo de los músculos tanto en la región dorsal como en la ventral.

SUMMARY: Works conducted on batoids have revealed large variations in the musculature of the ventral cephalic region, associated to the different lifestyles of these organisms and, therefore, to their feeding mechanisms. This work aimed to conduct a comparative study of the dorsal and ventral cephalic muscular morphology of two species of the family Narcinidae: Narcine vermiculatus and Diplobatis ommata. It was observed that both species share a common morphological pattern. Muscles with larger variations in the dorsal region were the rostral depressor, the lateral preorbital and the rostral elevator. The most relevant difference in this region between both species was the absence of the cucularis muscle in D. ommata. In the ventral region, the main differences were observed in the mandibular depressor, medial preorbital, interbranchial and hyomandibular depressor muscles. In D. ommata, the latter is formed by two packages, and by one in N. vermiculatus. It can be concluded that the cephalic musculature is constant; however, significant differences are observed in the muscle development degree in both the dorsal and the ventral regions.

Two new species of Pharaxonothinae beetles (Coleoptera: Erotylidae) inhabiting cones of the cycad Ceratozamia santillanii Prez-Farr. amp; Vovides (Cycadales: Zamiaceae) in Mexico.

Two beetles, Ceratophila (Vovidesa) chipjonesi, new species, and Pharaxonotha perezi, new species, (Coleoptera: Erotylidae: Pharaxonothinae) are described from the male cones of the New World cycad Ceratozamia santillanii Prez-Farr. Vovides (Cycadales: Zamiaceae). Morphological analysis and keys are provided for distinguishing these from related beetles inhabiting Ceratozamia in Mexico.

Recent Advances on O-Ethoxycarbonyl and O-Acyl Protected Cyanohydrins.

Ethoxycarbonyl cyanohydrins and O-acyl cyanohydrins are examples of O-protected cyanohydrins in which the protecting group presents an electrophilic center, contributing to additional reaction pathways. The first section of this review describes recent advances on the synthesis of O-ethoxycarbonyl and O-acyl protected cyanohydrins. Reactions using KCN or alkyl cyanoformates as the cyanide ion source are described, as well as organic and transition metal catalysis used in their preparation, including asymmetric cyanation. In a second part, transformations, and synthetic applications of O-ethoxycarbonyl/acyl cyanohydrins are presented. A variety of structures has been obtained starting from such protected cyanohydrins and, in particular, the synthesis of oxazoles, 1,4-diketones, 1,3-diketones, 2-vinyl-2-cyclopentenones through various methods are discussed.

Histopathological Correlation (World Health Organization Classification) of Meningiomas and Their Anatomical Localization: A Multicenter Epidemiological Study in Mexico.

OBJECTIVE: To determine the epidemiology of the localization and histological type of meningiomas in the Mexican population and the distribution of the different histological patterns and their relationship to tumor localization and patient demographics. METHODS: A retrospective analysis was performed in 5 hospitals in Mexico from 2009 to 2019. For qualitative variables, mean values were compared using Pearson χ2 test for the correlation between location and histological pattern as well as the clinical presentation and the patient's sex. Student t test was performed for age and its correlation with location and histology. RESULTS: Analysis of 179 patients revealed significant differences in histopathological pattern, patient sex, and tumor location. No significant differences were found for age or clinical presentation in association with any specific histological pattern. CONCLUSIONS: There was a correlation between the histology of the 15 histopathological varieties of meningiomas and the predilection site of appearance as well as certain demographic aspects, such as sex. This study lays the foundation for future studies in Mexico on the differentiation and typing of meningiomas regardless of the histological grade to which they belong, as the exact behavior of these tumors, including grade I tumors, remains unknown to date.

Taxonomic updates in Amphitecna (Bignoniaceae): A new Mexican species and the re-establishment of the giant-leaved A. megalophylla.

In this study, we analyzed the morphological affinities of the 24 species of Amphitecna based on detailed morphological studies and multivariate cluster analyses. Our results suggest that the genus Amphitecna includes six morphological groups that can be easily distinguished based on floral and fruits characteristics: A. donnell-smithii group, A. macrophylla group, A. megalophylla group, A. molinae group, A. spathicalyx group, and A. steyermarkii group. A new species from Mexico, Amphitecna fonceti, is described. This new species is clearly differentiated by the predominantly ramiflorous inflorescences bearing multiple flowers per shoot, buds rounded at the apex, large flowers with a transverse fold in the corolla throat, calyx surface pubescent and strongly costate, and fruits elliptic, apiculate at the apex. We discuss the characteristics of each morphological group and their geographical distribution, provide a detailed description of the new species including ethnobotany notes, and propose the re-establishment of the giant-leaved species A. megalophylla.

Neuroanatomy of two species of genus Myliobatis (Chondrichthyes: Myliobatoidea) / Neuroanatomía de dos especies del género Myliobatis (Chondrichthyes: Myliobatoidea)

Several studies on the elasmobranchs neuroanatomy have shown that their brain is more complex than previously thought, and had significant intra and interspecific variations. The objective of this work was conducting a comparative encephalic neuroanatomy study of two species of genus Myliobatis. In total, 16 organisms of genera Myliobatis californica and Myliobatis longirostris, collected in the coasts of Kino Bay, Sonora, Mexico, were used. In Myliobatis, the brain has a long telencephalon and the posterior central nucleus is poorly developed. Their cerebellum is asymmetric, has several sulci, most of which are transversally oriented, with four lobes (anterior, medium and two posterior), a condition which has not been reported for any other species. It was observed that, despite the morphology of M. californica and M. longirostris is similar, there are some significant differences. Both species have moderate foliation, but M. californica has more sulci. In the diencephalon of M. californica, it was observed that the lobes of the infundibulum are oval-shaped and separated, while in M. longirostris, such lobes are rounded and near the medium line. It has to be highlighted that Myliobatis belongs to the most derived batoid group; nevertheless, its brain is considerably less complex, as compared to what has been reported for the most derived milyobatoids species.

Diversos estudios sobre la neuroanatomía de los elasmobranquios han demostrado que el cerebro es más complejo de lo que se pensaba y presenta considerables variaciones tanto intra como interespecíficas. El objetivo de este trabajo fue realizar un estudio de neuroanatomía comparada del encéfalo de dos especies del género Myliobatis. Se utilizaron un total de 16 organismos de Myliobatis californica y Myliobatis longirostris, los cuales fueron colectados en las costas de Bahía Kino, Son., México. El cerebro de Myliobatis tiene un telencéfalo largo, el núcleo central posterior está poco desarrollado; el cerebelo es asimétrico, presenta surcos que en su mayoría están orientados transversalmente, con cuatro lóbulos (anterior, medio y dos posteriores), condición que no ha sido reportada para otra especie. Se observó que, aunque M. californica y M. longirostris presentan una morfología similar existen ciertas diferencias. En ambas especies presentan una foliación moderada; sin embargo, en M. californica se observan más surcos. En el diencéfalo de M. californica se observa que los lóbulos del infundíbulo son ovalados y están separados, mientras que en M. longirostris son redondeados y se encuentran próximos a la línea media. Es importante señalar que, pese a que Myliobatis pertenece al grupo de batoideos más derivado, su cerebro es considerablemente menos complejo de lo que se ha reportado para las especies de miliobatoideos más derivadas.

Carbon dioxide adsorption on a modified zeolite with sodium dodecyl sulfate surfactants: A molecular dynamics study.

Molecular dynamics simulations are carried out to study adsorption of Carbon dioxide (CO2) in a zeolite modified with anionic surfactants at different gas concentrations. Sodium dodecyl sulfate (SDS) surfactant is used and simulations at different SDS concentrations were conducted. The results show that adsorption of the gas is influenced by the amount of SDS on the zeolite surface. In addition, gas retention inside and outside the solid is observed and it strongly depends on the free sodium ions in the zeolite. The most favorable adsorption takes place at low CO2 concentrations with few SDS molecules. Adsorption was studied in terms of density profiles and pair correlation functions and strong interactions of the CO2 molecules with the sodium ions were observed.

La rehabilitación física como componente de la atención educativa integral por vía ambulatoria a los alumnos con discapacidades motrices / Physical rehabilitation as a component of the integral educative attention by itinerant way for students with motor handicap

RESUMEN Introducción: la atención educativa integral, por vía ambulatoria a los alumnos con discapacidades motrices, incluye aspectos de la rehabilitación física que complementan los tratamientos que reciben en las instituciones de salud. Objetivo: caracterizar el desempeño motor y algunas de sus implicaciones en el desempeño escolar y social después de haber implementado una estrategia de rehabilitación desde la Educación Física por vía ambulatoria. Materiales y métodos: se realizó un estudio observacional descriptivo sobre las principales afectaciones del desempeño motor de los alumnos con discapacidades motrices residentes en los municipios Pinar del Río, Consolación del Sur y Los Palacios, que reciben atención educativa por vía ambulatoria, durante el período: septiembre de 2016 a julio de 2017, para lo cual se tomó una muestra de 16 alumnos con niveles de discapacidad tipificadas de moderada y severa. Se exploraron los contenidos psicomotrices, la postura, la presencia de contracturas y deformidades, la movilidad, el desarrollo de habilidades sustitutivas y el uso de apoyos. En el estudio, se realizó la observación participante durante la aplicación de la escala de la función motora modificada, test motor de Ozeretsky y el test de análisis cualitativo. Resultados: la valoración inicial de la muestra arrojó que los 16 alumnos presentan insuficiente desarrollo de los contenidos psicomotrices; nueve tienen afectaciones de la postura, seis presentan deformidades y contracturas y ocho manifiestan dificultades en la marcha. En la evaluación final, el 100 %, manifestó cambios favorables en todos los indicadores. Conclusiones: la implementación de la estrategia logró cambios significativos en el desarrollo motor de los alumnos, que contribuyeron a elevar su calidad de vida.

ABSTRACT Introduction: integral educative attention by itinerant way for motor handicapped students includes aspects from physical rehabilitation which complement all treatments they receive at medical centers. Objective: to characterize the acting motor and some of their implications in the school and social acting after having implemented a rehabilitation strategy from the Physical Education by itinerant way. Method and material: a descriptive study was made about main problems in motor performance of motor handicapped students who live in Pinar del Rio, Consolación del Sur and Los Palacios municipalities and receive educative attention by itinerant way. The study was made among September, 2015 - July, 2016 and on it were included 16 students with moderate and severe handicap. Psychomotor content, posture, presence of deformity and contractures, substitution skills and the use of supports were explored. An observation was also made while doing The modified motor function scale, Ozeretsky Motoric test and qualitative analysis Test. Results: under the initial view of the students involved, we established that 15 of them showed a low level in psychomotor contents, 9 of them had posture problems, 6 showed deformity and contractures and 8 had problems to walk. In the final evaluation the 100 % showed positive changes in all indicators. Conclusions: running with the strategy brought significant changes about the motor development in students, contributing to improve their quality of life.

New Force Field Parameters for the Sodium Dodecyl Sulfate and Alpha Olefin Sulfonate Anionic Surfactants.

Molecular dynamics simulations were carried out to obtain new force field parameters of two most commonly used anionic surfactants: sodium dodecyl sulfate and alpha olefin sulfonate. The present united atom models, of those surfactants, fail to reproduce one of the most important thermodynamic properties, the surface tension. Therefore, by scaling the Lennard-Jones parameters, the potential well (ϵ) and the length (σ), we were able to fit the experimental data. The correct micelle structure of the surfactants was also captured with the new set of parameters. The new proposed united atom models of both surfactants were tested with two different water models, TIP4P/ϵ and SPC/E, and good agreement with actual experiments was found.

Skeleton anatomy of five species of Genus urotrygon (Chondrichthyes: Urotrygonidae) / Anatomía del esqueleto de cinco especies del género Urotrygon (Chondrichthyes: Urotrygonidae)

Skeleton of batoids has been important to outline kinship relations in this group. Therefore, the objective of this work is describing the anatomy of five species of genus Urotrygon. Skeleton of Urotrygonids displayed a common morphological pattern, with the following differences: 1) preorbital processes are reduced in Urotrygon nana and Urotrygon munda, and developed on all other species; 2) the first postorbital process is reduced in U. nana and U. munda; 3) the first hypobranchial cartilage is fragmented only in Urotrygon rogersi; 4) only Urotrygon aspidura had a bridge in the basibranchial cartilage; lateral processes of the synarcuale in U. aspidura are long and thin, while short and wide in U. nana and U. rogersi; 6) U. nana has only one single fenestra in its pectoral girdle, while other species have two; 7) In U. nana and U. munda the mesopterygium is rounded, but in all other species it is elongated in its anterior part; 8) U. nana y U. munda have a more arched pelvic girdle. Species with more plesiomorphic characters are U. nana and U. munda.

El esqueleto de los batoideos ha sido importante para establecer las relaciones de parentesco de este grupo. Es por ello que el objetivo del presente trabajo fue describir la anatomía de cinco especies del género Urotrygon. El esqueleto de las especies de urotrigonidos mostró un patrón morfológico común; sin embargo, se observaron las siguientes diferencias: 1) los procesos preorbitales están reducidos en Urotrygon nana y Urotrygon munda, en el resto de las especies están más desarrollados. 2) El primer proceso postorbital está reducido en U. nana y U. munda. 3) El primer cartílago hipobranquial se fragmenta únicamente en Urotrygon rogersi. 4) Solo en Urotrygon aspidura el cartílago basibranquial presentó un puente. 5) Los procesos laterales de la sinarcualia en U. aspidura son largos y delgados, mientras que en U. nana y U. rogersi son anchos y cortos. 6) En la cintura pectoral U. nana presenta una sola fenestra, en el resto de las especies hay dos. 7) En U. nana y U. munda el mesopterigio es redondeado, en el resto de las especies está alargado en su parte anterior. 8) La cintura pélvica está más arqueada en U. nana y U. munda. Las especies que presentaron los caracteres más plesiomórficos fueron U. nana y U. munda.

Effect of plant growth-promoting bacteria on the growth and fructan production of Agave americana L

ABSTRACT The effect of plant growth-promoting bacteria inoculation on plant growth and the sugar content in Agave americana was assessed. The bacterial strains ACO-34A, ACO-40, and ACO-140, isolated from the A. americana rhizosphere, were selected for this study to evaluate their phenotypic and genotypic characteristics. The three bacterial strains were evaluated via plant inoculation assays, and Azospirillum brasilense Cd served as a control strain. Phylogenetic analysis based on the 16S rRNA gene showed that strains ACO-34A, ACO-40 and ACO-140 were Rhizobium daejeonense, Acinetobacter calcoaceticus and Pseudomonas mosselii, respectively. All of the strains were able to synthesize indole-3-acetic acid (IAA), solubilize phosphate, and had nitrogenase activity. Inoculation using the plant growth-promoting bacteria strains had a significant effect (p < 0.05) on plant growth and the sugar content of A. americana, showing that these native plant growth-promoting bacteria are a practical, simple, and efficient alternative to promote the growth of agave plants with proper biological characteristics for agroindustrial and biotechnological use and to increase the sugar content in this agave species.

A new species of Amphitecna (Bignoniaceae) endemic to Chiapas, Mexico.

Amphitecna loreae Ortiz-Rodr. & Burelo, sp. nov. (Bignoniaceae), a new species endemic to the karst rainforest in southern Mexico, is described and illustrated. The new species differs from the other species of Amphitecna by the combination of cauliflorous inflorescences, larger flowers, buds rounded at apex, and globose-ellipsoid rather than acuminate fruits. A key to the Mexican species of Amphitecna is presented.

Effect of plant growth-promoting bacteria on the growth and fructan production of Agave americana L

The effect of plant growth-promoting bacteria inoculation on plant growth and the sugar content in Agave americana was assessed. The bacterial strains ACO-34A, ACO-40, and ACO-140, isolated from the A. americana rhizosphere, were selected for this study to evaluate their phenotypic and genotypic characteristics. The three bacterial strains were evaluated via plant inoculation assays, and Azospirillum brasilense Cd served as a control strain. Phylogenetic analysis based on the 16S rRNA gene showed that strains ACO-34A, ACO-40 and ACO-140 were Rhizobium daejeonense, Acinetobacter calcoaceticus and Pseudomonas mosselii, respectively. All of the strains were able to synthesize indole-3-acetic acid (IAA), solubilize phosphate, and had nitrogenase activity. Inoculation using the plant growth-promoting bacteria strains had a significant effect (p 0.05) on plant growth and the sugar content of A. americana, showing that these native plant growth-promoting bacteria are a practical, simple, and efficient alternative to promote the growth of agave plants with proper biological characteristics for agroindustrial and biotechnological use and to increase the sugar content in this agave species.(AU)

Effect of plant growth-promoting bacteria on the growth and fructan production of Agave americana L.

The effect of plant growth-promoting bacteria inoculation on plant growth and the sugar content in Agave americana was assessed. The bacterial strains ACO-34A, ACO-40, and ACO-140, isolated from the A. americana rhizosphere, were selected for this study to evaluate their phenotypic and genotypic characteristics. The three bacterial strains were evaluated via plant inoculation assays, and Azospirillum brasilense Cd served as a control strain. Phylogenetic analysis based on the 16S rRNA gene showed that strains ACO-34A, ACO-40 and ACO-140 were Rhizobium daejeonense, Acinetobacter calcoaceticus and Pseudomonas mosselii, respectively. All of the strains were able to synthesize indole-3-acetic acid (IAA), solubilize phosphate, and had nitrogenase activity. Inoculation using the plant growth-promoting bacteria strains had a significant effect (p<0.05) on plant growth and the sugar content of A. americana, showing that these native plant growth-promoting bacteria are a practical, simple, and efficient alternative to promote the growth of agave plants with proper biological characteristics for agroindustrial and biotechnological use and to increase the sugar content in this agave species.

Adsorption of phenol molecules by sodium dodecyl sulfate (SDS) surfactants deposited on solid surfaces: A computer simulation study.

Adsorption studies of phenol molecules on a sodium dodecyl sulfate (SDS) micelle were investigated by molecular dynamics simulations. Simulations were carried out in bulk and on three distinct solid surfaces, silicon dioxide, titanium dioxide and graphite. It was observed that different surfactant micellar shapes were formed on the surfaces. For the silicon dioxide and titanium dioxide surfaces the surfactants were adsorbed by their headgroups whereas for the graphite surface they were adsorbed mainly by their tail groups. It was found that the amount of phenol adsorbed on the SDS micelle was altered by the surfactant shape deposited on the solid surface. However, the best phenol adsorption was obtained by the surfactant modified silicon dioxide surface. Moreover, in all cases, from structural investigations, it was determined that the phenol molecules were located inside the surfactant micelle with their hydroxyl groups close to the SDS headgroups.

Compared morphology of the cephalic musculature in five species of genus Urotrygon (Chondrichthyes: Urolophidae) / Morfología comparada de la musculatura cefálica de cinco especies del género Urotrygon (Chondrichthyes: Urolophidae)

This work aims to describe the morphology of dorsal and ventral cephalic musculature in five species of genus Urotrygon. Muscular differences were observed, mainly in the development level. Muscles showing certain degree of variation in the dorsal region were the cucullaris and the ethmoideo-parethmoidalis. In ventral view, higher variation was observed. Muscles showing differences were the depressor rostri, the depressor hyomandibularis, the preorbitalis medial, the coracohioideus, and the depressor mandibularis. Urotrygon aspidurus was the species with the largest differences, as it has no mandibular depressor, and the rostral depressor is quite developed. The shape and arrangement of cephalic musculature in Urotrygon is similar to that reported for genus Urolophus and Dasyatis, however, it is different from that of most specialized myliobatoids.

El presente trabajo tiene por objetivo describir la morfología de la musculatura cefálica dorsal y ventral de cinco especies del género Urotrygon. En los músculos de la región cefálica dorsal y ventral se observaron diferencias, principalmente en el grado de desarrollo. Los músculos que mostraron cierto grado de variación en la región dorsal fueron el cucularis y el etmoideo paraetmoidal. En vista ventral los músculos que mostraron diferencias fueron el depresor rostral, el depresor hiomandibular, el preorbitalis medial, el coracohioideus y el depresor mandibular. Urotrygon aspidurus fue la especie que mostró mayores diferencias ya que no presenta el músculo depresor mandibular, y el depresor rostral está muy desarrollado. La forma y disposición de la musculatura cefálica de Urotrygon es similar a la reportada para especies de los géneros Urolophus y Dasyatis, sin embargo, es diferente a la de los miliobatoideos más especializados.

Relación entre riesgos del ambiente laboral y salud en fumigadores. Presentación de un caso / Relationship between working environment risks and health in fumigators. A case presentation

Este estudio consiste en realizar un análisis del impacto a la salud que pueden presentar los operarios de control de vectores en nuestro país, que se exponen a varios factores de riesgos durante el desempeño de su labor, como el ruido, los plaguicidas, las vibraciones y los riesgos ergonómicos. Tomamos como ejemplo para el mismo la presentación de un caso y tratamos de encontrar una explicación fisiopatología de lo que ocurrió en el aparato auditivo de este operario(AU)

Gas sorption in solid surfaces: a computational study using rigid and Einstein-solid models.

The reactive Monte Carlo (RxMC) method was proposed to describe the sorption of gases in solid materials due to the chemical reaction A + B ⇌ C. Two models were used to simulate the solid; the first model considered simulations with rigid particles in the solid whereas in the second model the particles were allowed to vibrate inside the solid with a given spring constant, i.e. an Einstein solid was used to simulate the substrate. In both models not only physisorption but also chemisorption of the fluid was observed. Sorption curves, at different spring constants, were simulated and it was noted that sorption was always enhanced with the Einstein solid model. Moreover, an inverse dependent function of the spring constant with the temperature was found. Finally, the second model might be used to explain the unusual sorption behavior observed in actual experimental reactions such as CO2 + Li2O ⇌ Li2CO3.