RESUMO
A novel robot gripper control system is presented that uses PVDF (polyvinylidene fluoride) piezoelectric sensors to damp exerted force actively. By monitoring the current developed by the PVDF sensor, an output proportional to the rate of change of the force exerted by the gripper is obtained. The signals from the PVDF sensor and strain-gauge force sensor are arranged in a proportional and derivative control system for the control of force. The control system was tested on an instrumented Rhino XR-1 manipulator hand. The capabilities of the control system are analyzed and are verified experimentally. The results for this particular gripper indicate that the additional sensory feedback can decrease the force step response rise time by 88% while maintaining a monotonic zero-overshoot response. The inclusion of the rate feedback increases the damping ratio of the dominant poles while maintaining the step response rise time.
RESUMO
Head computed tomographic (CT) examinations of 14 patients with primary brain lymphoma were reviewed to assess the CT features of the presenting and subsequent lesions. Presenting lesions were single in 62% and multiple in 38%. Lesions tended to be iso- or hyperdense and homogeneously enhancing. They were commonly located in the deep hemispheric regions, corpus callosum, and posterior fossa. Despite these characteristic patterns, the diagnosis of lymphoma was initially considered in just three patients. Follow-up CT showed good initial response to radiotherapy in 10 patients although mortality was high and posttherapy changes were frequent. Consideration of primary brain lymphoma by radiologists is important, as needle biopsy and radiotherapy may be preferred to a surgical resection.
Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Linfoma/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Adulto , Idoso , Neoplasias Encefálicas/mortalidade , Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/terapia , Terapia Combinada , Feminino , Seguimentos , Humanos , Linfoma/mortalidade , Linfoma/radioterapia , Linfoma/terapia , Masculino , Pessoa de Meia-Idade , Recidiva Local de NeoplasiaRESUMO
A congenitally patent ductus venosus is the rarest form of portosystemic shunt. Although it occurs in the absence of serious parenchymal liver disease, it may be associated with hepatic encephalopathy. This case report describes a 49-year-old man with a patent ductus venosus who presented with recurrent bouts of encephalopathy but few other features of chronic liver disease. Ligation of the shunt was followed by life-threatening complications. The portal venous system must be carefully assessed before closure of a patent ductus venosus is attempted.