Abstract: Forest fuel is one of the main carbon pools, but is also considered a factor involved in the occurrence and intensity of forest fires. The objective of this study was to analyze the temporal dynamics of forest fuel storage and the effect of fire in a pine (Pinus oocarpa Schiede) forest. The measurement of fresh and decomposed litter, and woody materials was carried out from 2010 to 2021 at four sites of a pine forest in the Cerro Nambiyugua, Villaflores, Chiapas, with the National Forest and Soil Inventory method. At each site, eight 30 x 30 cm2 quadrants were used to collect litter samples. To dry the samples, paper bags were used and placed in an oven at 70°C for 72 hours. The fallen woody material was sampled with the line intersection method. Fresh and decomposed litter load increased gradually over time. The highest litter loads were obtained in 2018 with 12.67 t ha-1. After the forest fire in 2019, the litter load decreased to 5.67 t ha-1, and by 2021 it increased to 8.65 t ha-1. The accumulation trend of fallen woody material varied according to the category of ignition hours. The results of this study have fundamental implications in the strategies and periodicity of forest fuel load management and carbon storage, since a greater frequency of forest fires is expected with climate change.

Resumen: Los combustibles forestales son uno de los principales reservorios de carbono, pero también se consideran un factor involucrado en la ocurrencia e intensidad de incendios forestales. El objetivo de este estudio fue analizar la dinámica temporal de almacenamiento y efecto del incendio sobre los combustibles forestales en bosque de pino (Pinus oocarpa Schiede). La medición de hojarasca, mantillo y materiales leñosos se realizó de 2010 a 2021 en cuatro sitios de un bosque de pino del Cerro Nambiyugua, Villaflores, Chiapas con el método del Inventario Nacional Forestal y de Suelos. En cada sitio, se utilizaron ocho cuadrantes de 30 x 30 cm2 para colectar las muestras de hojarasca y mantillo. Para el secado de las muestras, se utilizaron bolsas de papel estraza y se colocaron en estufa a 70°C durante 72 horas. El material leñoso caído se determinó con la metodología de intersección planar. La carga de hojarasca y mantillo aumentó gradualmente con el tiempo. Las mayores cargas de hojarasca se obtuvieron en el año 2018 con 12.67 t ha-1. Después del incendio forestal del año 2019, la carga de hojarasca disminuyó a 5.67 t ha-1, y para el 2021 aumento a 8.65 t ha-1. La tendencia de acumulación de material leñoso caído varió según la categoría de horas de ignición. Los resultados de este estudio tienen implicaciones fundamentales en las estrategias y periodicidad del manejo de carga de combustibles forestales y almacenamiento de carbono ya que con el cambio climático se espera mayor frecuencia de incendios forestales.

Abstract The use of Bt soybean resulted in an important advance in the control of pests that affect this crop. However, in recent years there has been an increase in damage caused by lepidopteran species not targeted by this technology; among them Spodoptera cosmioides (Walker). This work analyzed the development of immature stages of S. cosmioides reared on two different substrates: Amaranthus spp. and Bt soybean. Newly hatched larvae of the F1 obtained from collections in commercial fields of Bt soybean in the province of Tucumán, Argentina were used. For each substrate, 100 larvae were reared individually throughout their development. The occurrence of molts was recorded daily and the cephalic capsules were kept for measurement. Once the pupal stage was completed, pupae were weighed and the sex was determined. With the number of adults obtained, the viability of the pupal stage was determined. The duration of the larval stadiums presented statistically significant differences for the L2, L6 and L7 stadiums. Overall, the length of the larval stage was slower in Bt soybean; which, in turn, featured additional stadiums. The width of the cephalic capsules showed statistically significant differences in L2 and L5. The pupae from larvae fed Bt soybean were lighter than those of Amaranthus spp. For the duration of the pupal stage the differences were not statistically significant. There were no statistically significant differences attributable to the substrate for the sex ratio and for the survival analysis (Kaplan-Meier). The results show that Bt soybean are a less appropriate substrate for the development of S. cosmioides than Amaranthus spp.

Resumen El uso de soja Bt resultó en un avance importante en el control de plagas que afectan este cultivo. Sin embargo, en los últimos años se observó un incremento del daño producido por especies de lepidópteros no blanco de esta tecnología; entre ellas Spodoptera cosmioides (Walker). Este trabajo analizó el desarrollo de estados inmaduros de S. cosmioides criada en dos sustratos diferentes: Amaranthus spp. y soja Bt. Se utilizaron larvas recién eclosionadas de la F1 obtenida de recolecciones en campos comerciales de soja Bt en la provincia de Tucumán, Argentina. Para cada sustrato se partió de 100 larvas que fueron seguidas a lo largo de su desarrollo en forma individual. Diariamente se registró la ocurrencia de mudas y se conservaron las cápsulas cefálicas para su medición. Una vez completado el estado de pupa se pesaron las mismas y se determinó el sexo. Con el número de adultos obtenidos se determinó la viabilidad del estado de pupa. La duración de los estadios larvales, presentó diferencias estadísticamente significativas para los estadios de L2, L6 y L7. En su conjunto, la duración del estado larval fue más lento en soja Bt; que a su vez, presentó estadios adicionales. El ancho de las cápsulas cefálicas mostró diferencias estadísticamente significativas en L2 y L5. Las pupas provenientes de larvas alimentadas con soja Bt fueron más livianas que las de Amaranthus spp. Para la duración del estado de pupa las diferencias fueron estadísticamente no significativas. No se observaron diferencias estadísticamente significativas atribuibles al sustrato para relación de sexos y para el análisis de sobrevida (Kaplan-Meier). Los resultados muestran que la soja Bt resulta un sustrato menos apropiado para el desarrollo de S. cosmioides que Amaranthus spp.

ABSTRACT This study estimated the population density of Spondylus limbatus at six fishing banks that are representative of the Gulf of California, Mexico. Each bank was identified in July 2011. There were significant differences in density between banks, and a steady north-to-south decrease in density that was fitted to a potential model. At low densities, S. limbatus showed a lower variability in size. Since the densities of S. limbatus are suitable for commercial exploitation, sustainable extraction can be performed under a population recovery approach. Also, this study represents a baseline for the evaluation and monitoring of populations of this species through time and contributes to set general guidelines for the assessment of commercial feasibility and exploitation criteria.

The Magnetic Resonance Imaging (MRI) is a non-invasive technique which uses the physical phenomenon of nuclear magnetic resonance to obtain structural and compositional information about human body regions. In this imaging study we use the radio-frequency and a powerful static magnetic field, which aligns the magnetization of hydrogen nuclei. Nowadays there are many types of clinical equipment that conduct MRI studies, which have intensities of magnetic fields from 0.2T to 7.0T. Moreover, liquid helium is required for the superconducting coil. This paper presents an analysis of the magnetic resonance phenomenon; by doing a review of the quantum-mechanical aspects as the spin and Zeeman effect.

Angiotensin-(1-7) (Ang-(1-7)) increased osmotic water permeability in the isolated toad skin, a tissue with functional properties similar to those of the distal mammalian nephron. Concentrations of 0.1 to 10 µM were effective, with a peak at 20 min. This effect was similar in magnitude to that of frog skin angiotensin II (Ang II) and oxytocin but lower than that of human Ang II and arginine-vasotocin. The AT2 angiotensin receptor antagonist PD 123319 (1.0 µM) fully inhibited the response to 0.1 µM Ang-(1-7) but had no effect on the response to Ang II at the same concentration. The specific receptor antagonist of Ang-(1-7), A-779, was ineffective in blocking the response to Ang-(1-7) and to frog skin Ang II. The AT1 receptor subtype antagonist losartan, which blocked the response to frog skin Ang II, was ineffective in blocking the response to Ang-(1-7). The present results support the view of an antidiuretic action of Ang-(1-7) in the mammalian nephron.