RESUMEN
Predictions from forest ecosystem models are limited in part by large uncertainties in the current state of the land surface, as previous disturbances have important and lasting influences on ecosystem structure and fluxes that can be difficult to detect. Likewise, future disturbances also present a challenge to prediction as their dynamics are episodic and complex and occur across a range of spatial and temporal scales. While large extreme events such as tropical cyclones, fires, or pest outbreaks can produce dramatic consequences, small fine-scale disturbance events are typically much more common and may be as or even more important. This study focuses on the impacts of these smaller disturbance events on the predictability of vegetation dynamics and carbon flux. Using data on vegetation structure collected for the same domain at two different times, i.e. "repeat lidar data", we test high-resolution model predictions of vegetation dynamics and carbon flux across a range of spatial scales at an important tropical forest site at La Selva Biological Station, Costa Rica. We found that predicted height change from a height-structured ecosystem model compared well to lidar measured height change at the domain scale (~150 ha), but that the model-data mismatch increased exponentially as the spatial scale of evaluation decreased below 20 ha. We demonstrate that such scale-dependent errors can be attributed to errors predicting the pattern of fine-scale forest disturbances. The results of this study illustrate the strong impact fine-scale forest disturbances have on forest dynamics, ultimately limiting the spatial resolution of accurate model predictions.
Asunto(s)
Ciclo del Carbono/fisiología , Árboles/fisiología , Costa Rica , Ecosistema , Bosques , Modelos TeóricosRESUMEN
Oxygen-derived free radical damage is associated with the molecular toxicity of hemoglobin. Especially in thalassemia syndromes, this toxicity has a relationship with "free" alpha globin concentrations. This study of beta thalassemia trait blood samples from 39 individuals shows that the evaluation of methemoglobin is a sensitive method of indicating molecular toxicity and the superoxide dismutase concentration revealing the intensity of oxidative stress of this process.
Asunto(s)
Humanos , Talasemia beta , Técnicas de Laboratorio Clínico , Eritrocitos/metabolismo , Talasemia/metabolismoRESUMEN
The therapeutic efficacy of thalidomide in erythema nodosum leprosum suggests that thalidomide might play a useful therapeutic role in other human immune-complex diseases. Thalidomide has shown anti-inflammatory or immunosuppressive actions in several animal models. Current evidence suggests that its rapid activity in ENL may result from suppression of neutrophil chemotaxis and phagocytosis. Scattered anecdotal clinical reports of apparent response to thalidomide in various autoimmune diseases are hardly conclusive, but underline the desirability of appropriate pilot trials of thalidomide in autoimmune diseases, particularly those in which immune complex deposition plays a prominent role. Provided that a contraindication in fertile women is strictly observed, thalidomide therapy appears to be quite safe.
Asunto(s)
Femenino , Humanos , Animales , Cobayas , Ratas , Enfermedades Autoinmunes/tratamiento farmacológico , Enfermedades de los Animales/tratamiento farmacológico , Modelos Animales de Enfermedad , Rechazo de Injerto , Talidomida/uso terapéutico , Inflamación/tratamiento farmacológico , Inflamación/veterinariaRESUMEN
Three groups of Portuguese-, Mexican-, and Anglo-American boys and girls (N - 158) from 5th through 8th grade were compared in self-esteem. The results of the chi square test indicated that there were no significant differences between Mexican and Anglo Ss. However, significant differences were observed when the Portuguese Ss were compared to the other two groups. Here it was discovered that Portuguese boys--but not girls--had significantly higher self-esteem than all other Ss.