RESUMO
An intruder penetrating into a granular column experiences a depth-dependent friction force F(z). Different regimes of F(z) have been measured depending on the experimental design: a nearly linear dependence for shallow penetrations, total saturation at large depths, and an exponential increase when the intruder approaches the bottom of the granular bed. We report here an experiment that allows us to measure the different regimes in a single run during the quasistatic descent of a sphere in a light granular medium. From the analysis of the resistance in the saturation zone, it was found that F(z) follows a cube-power-law dependence on the intruder diameter and an exponential increase with the packing fraction of the bed. Moreover, we determine the critical mass m_{c} required to observe infinite penetration and its dependence on the above parameters. Finally, we use our results to estimate the final penetration depth reached by intruders of masses m
RESUMO
AIMS: To describe the pathophysiology, diagnosis and clinical manifestations of the neurological complications that critically ill patients often develop in intensive care units, and to discuss their treatment and prognosis, in the light of the most significant contemporary literature. DEVELOPMENT: The most frequent complication suffered by critically ill patients is sepsis, with encephalopathy as the main manifestation, and this has a direct effect on their prognosis. Polyneuropathy of the critically ill patient is linked to sepsis, as the main precipitating factor, as well as to the presence of high levels of glucose, which plays an important role in deciding whether mechanical ventilation can be withdrawn or not. Myopathy of the critically ill patient is related to the use of fluorinated steroids and neuromuscular blockers, which are frequently administered to these patients. All these entities represent a significant diagnostic challenge for the physician and are accompanied by important sequelae that continue after the patient's discharge from hospital, as well as myopathies and neuropathies associated to the use of drugs that are commonly administered to critically ill patients. It is therefore necessary to be familiar with the pathophysiology of the damage and with the associated factors, if a suitable diagnostic approach is to be employed. CONCLUSIONS: The incidence of these pathologies and their complications makes them important conditions that require a swift, accurate diagnosis so that treatment can be established early on and a prognosis can also be determined.