Abstract
The
milpa
agroecosystem is an intercropping of maize, beans, squash and other crops, developed in Mesoamerica, and its adoption is widely variable across climates and regions. An example of ...particular interest is the Yucatan Peninsula in Mexico, which holds highly diverse
milpas
, drawing on ancestral Mayan knowledge. Traditional
milpas
have been described as sustainable resource management models, based on long rotations within a slash-and-burn cycle in forest areas. Nevertheless, due to modernization and intensification processes, new variants of the approach have appeared. The objective of this study was to evaluate the sustainability of three
milpa
systems (traditional, continuous, and mechanized) in four case studies across the Peninsula, with emphasis on food self-sufficiency, social inclusion and adoption of innovations promoted by a development project. The Framework for the Evaluation of Agroecosystems using Indicators (MESMIS, for its Spanish acronym) was used for its flexible, participatory approach. A common group of indicators was developed despite regional differences between study cases, with a high level of farmer participation throughout the iterative process. The results show lower crop yields in traditional systems, but with lower inputs costs and pesticide use. In contrast, continuous
milpas
had higher value in terms of crop diversity, food security, social inclusion, and innovation adoption. Mechanized
milpas
had lower weed control costs. Profitability of cash crops and the proportion of forest were high in all systems. Highly adopted innovations across
milpa
types and study cases included spatial crop arrangement and the use of residues as mulches. However, most innovations are not adapted to local conditions, and do not address climate change. Further, women and youth participation is low, especially in traditional systems.
The presence of hard, brittle, thin White Etching Layers (WELs) on rail surfaces plays a critical role in varying the tribology behaviours at the wheel and rail interface. The reciprocating sliding ...tests were carried out on the rail samples covered with two types of WELs, including thermomechanically-induced WEL (TP-WEL) and mechanically-induced WEL (SD-WEL) at room temperature and 600 °C. A WEL-free rail sample was also employed for the comparison. The wear mechanism of WEL-free rail shifts from severe abrasive wear at room temperature to adhesive dominant wear at 600 °C. Under the pressurized sliding conditions of 1.2 GPa at 600 °C, the WEL-free rail was observed to form WEL and BEL. The pre-existed SD-WEL and TP-WEL on the rail samples could transform into worn WEL at the topmost contact rail surface with Brown Ething Layer (BEL) formation beneath it. The formation of BEL is attributed to the tempered effect on pre-existed WEL. Due to their high hardness, both SD-WEL and TP-WEL-covered rails exhibit minimal abrasive behaviours at room temperature while displaying adhesive dominant wear mechanisms at 600 °C. Of the two types of WELs, TP-WEL has lower wear resistance, whereas SD-WEL promotes high friction and reduces wear loss.
•Tribological behaviours of two distinct classes of White Etching Layers (WELs) on the rail surface were measured.•Tribological properties of the rail are dependent on the existence and type of WELs and the temperature at rail surface.•The pre-existed WELs could be transferred into worn WEL at the topmost contact and underlying Brown Etching Layer (BEL).•In comparison with mechanically-induced WEL, thermomechanically-induced WEL is more prone to be worn out during service.
This study aimed to determine the epidemiological, microbiological, and molecular characteristics of an outbreak of carbapenem-resistant Leclercia adecarboxylata in three hospitals associated with ...the unintended use of contaminated total parental nutrition (TPN).
For 10 days, 25 patients who received intravenous TPN from the same batch of a formula developed sepsis and had blood cultures positive for L. adecarboxylata. Antimicrobial susceptibility and carbapenemase production were performed in 31 isolates, including one from an unopened bottle of TPN. Carbapenemase-encoding genes, extended-spectrum β-lactamase-encoding genes were screened by PCR, and plasmid profiles were determined. Horizontal transfer of carbapenem resistance was performed by solid mating. Clonal diversity was performed by pulsed-field gel electrophoresis. The resistome was explored by whole-genome sequencing on two selected strains, and comparative genomics was performed using Roary.
All 31 isolates were resistant to aztreonam, cephalosporins, carbapenems, trimethoprim/sulfamethoxazole, and susceptible to gentamicin, tetracycline, and colistin. Lower susceptibility to levofloxacin (51.6%) and ciprofloxacin (22.6%) was observed. All the isolates were carbapenemase producers and positive for bla
, bla
, and bla
genes. One main lineage was detected (clone A, 83.9%; A1, 12.9%; A2, 3.2%). The bla
gene is embedded in a Tn125-like element. Genome analysis showed genes encoding resistance for aminoglycosides, quinolones, trimethoprim, colistin, phenicols, and sulphonamides and the presence of IncFII (Yp), IncHI2, and IncHI2A incompatibility groups. Comparative genomics showed a major phylogenetic relationship among L. adecarboxylata I1 and USDA-ARS-USMARC-60222 genomes, followed by our two selected strains.
We present epidemiological, microbiological, and molecular evidence of an outbreak of carbapenem-resistant L. adecarboxylata in three hospitals in western Mexico associated with the use of contaminated TPN.
Las actividades lúdico-deportivas contribuyen significativamente a la formación de valores. El objetivo fue fortalecer la tolerancia con estudiantes de 8° grado del Colegio Fundación Pies Descalzos ...de Barranquilla mediante un programa lúdico-deportivo de ultimate frisbee. Se trató de un estudio de enfoque cuantitativo y diseño preexperimental; en el que participaron 32 estudiantes, hombres y mujeres, con edades entre 13 y 15 años. Inicialmente se encontró que los estudiantes presentaban problemas de tolerancia, mediante la aplicación de una encuesta orientada a evaluar varios aspectos de conducta frente a las actitudes de sus compañeros y algunas condiciones del entorno, y la revisión del informe de convivencia y disciplina que realiza la institución periódicamente. En función de los resultados del diagnóstico, se diseñó y desarrolló en 24 sesiones un programa lúdico-deportivo de ultimate frisbee, basado en la práctica de sus fundamentos técnicos y principios de juego básicos. La objetividad del programa para la promoción de valores como la tolerancia, y la fiabilidad de la encuesta como instrumento para medir la tolerancia fueron avalados por expertos. Después se aplicó nuevamente la encuesta y se revisó el informe de convivencia, para valorar los efectos del programa, encontrándose que la mayoría de faltas relacionadas con la intolerancia disminuyeron significativamente. En conclusión, se fortaleció la tolerancia con los estudiantes a partir de la vivencia del programa, fundamentalmente en aspectos como la disminución de agresiones entre compañeros y el establecimiento de respuestas asertivas a las mismas, y un comportamiento más tolerante durante las clases de Educación Física.
A partir de muestras de trigo de la variedad CIRNO C2008 con síntomas de tizón foliar y provenientes del Sur de Sonora, México, se obtuvieron cuatro aislados de Bipolaris sorokiniana y cuatro de ...Alternaria alternata. Las especies fúngicas se identificaron mediante caracterización morfológica y análisis de secuencias ITS del DNA ribosomal. En invernadero, se inocularon los ocho aislados en 13 variedades de trigo harinero (Triticum aestivum) y 6 de trigo cristalino (Triticum durum). La agresividad de los aislados se evaluó con una escala de severidad de 1 a 9, donde 1 fue lesiones mínimas y 9 necrosis y clorosis generalizada que indicó susceptibilidad. Las variedades Vicam S70, Kronstad F2004 y Río Bravo C2016 fueron moderadamente resistentes a B. sorokiniana; en contraste, Bárcenas S2002, Morocco, Borlaug 100 F2014, Bacanora T88, Luminaria F2012, la línea avanzada C, Villa Juárez F2009, Maya S2007, Urbina S2007, PBW343, Nana F2007, Local red, Noio y la línea avanzada JC fueron altamente susceptibles. Adicionalmente, se observó que A. alternata es un patógeno secundario que invade las lesiones provocadas por B. sorokiniana.
RESUMEN Los objetivos de este estudio fueron identificar las especies de Fusarium causantes de pudrición de raíz en trigos producidos en el Bajío de México, además de determinar la respuesta de 28 ...variedades de trigo a la enfermedad. En 2014 y 2015 se obtuvieron aislados de Fusarium spp. a partir de muestras de trigo con síntomas de fusariosis. Los aislados fúngicos se identificaron mediante caracterización morfológica y análisis de secuencias ITS y TEF-1a, así como el uso de iniciadores específicos para la detección de especies de Fusarium. Un aislado representativo de cada especie de Fusarium obtenida se incrementó para verificar su patogenicidad a través de la inmersión de semillas de 28 variedades de trigo en una suspensión de conidios. Los resultados de la caracterización morfológica y análisis de secuencias, así como las pruebas de patogenicidad, indicaron que Fusarium proliferatum y F. graminearum son las principales especies causantes de la pudrición de raíz en trigo cultivado en el Bajío de México. Entretanto, la respuesta a la inoculación indicó que las variedades Gálvez M87, Castrejón F97 y Maya S2007 fueron las más tolerantes a la enfermedad, mientras que Monarca F2007 y Batán F96 fueron las variedades más susceptibles.
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