Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
84,984 records were found.
A system is conceived of as being slowly varying if it changes slowly enough to permit identification to within a specified error. A generic model is developed to study the identifiability and identification of slowly varying systems. The model is suitable for a large variety of nonlinear, time-varying, causal, bounded memory systems; it has finitely many parameters and is linear in its parameters. Results are obtained with the use of this general model that give guaranteed accuracy of identification as a function of the prior knowledge of the unknown system, the maximum rate of time variation of the system, and the characteristics of output observation noise. To derive these results, a recursive estimation procedure is developed for time-discrete linear dynamical system structures in which the observation noise is statistical but the ...
A morphological mutant of Neurospora crassa, snowflake, is shown to contain filaments which are about 70 A in diameter, and up to several microns long, and which usually bunch in groups of a few to several hundred. They may be found longitudinally or transversely arranged with respect to the long axis of the cell and, in many cases, they run up to the plasma membrane, but not through it. The filaments often are arranged in crystalline arrays but may also be found as separate filaments. Sometimes the filaments are closely appressed to nuclei and may be found inside them. It is likely that the filaments are not the result of the dissociation of microtubules and are most likely microfilaments like those found in other organisms. Their relationship to the origin of certain morphological mutants in Neurospora is discussed.
Evidence of circulating endotoxin was sought in children with Reye's syndrome, on the thesis that severe hepatic failure is likely to result in loss of capacity to detoxify intestinal endotoxins entering the circulation. A modification of the Limulus assay was used to demonstrate high levels of endotoxin-like activity (E.L.A.) in nine comatose patients with Reye's syndrome and in one of the two non-comatose patients. The symptom-free sibling of one patient had raised liver enzymes and a negative Limulus test. Plasma E.L.A. correlated significantly with degree of electroencephalographic disturbance early in the course of the illness. E.L.A. was also found in both of two cerebrospinal fluids evaluated. Preliminary in-vitro characterisation of this substance indicated that it resembled endotoxin derived from anaerobic intestinal bacteria....
A prospective double-blind trial of aspirin prophylaxis demonstrated a reduction of more than 50% in headache frequency in 9 of 12 migraine patients. Response to aspirin did not correlate with age, duration of headache history, family history, or platelet ultrastructure. There is some evidence that response to aspirin is associated with raised platelet aggregation. This pilot study indicates that aspirin is effective in migraine prophylaxis.
A toxin(s) has been demonstrated in the stools of two patients with antibiotic- associated colitis. This toxin(s) was heat-labile, wasrapidly lethal for hamsters, increased vascular permeability in rabbit skin, and was cytotoxic for cells in tissue-culture. It was neutralised by Clostridium sordellii antitoxin but not by antitoxins prepared against otherclostridia; Escherichia coli, and Vibrio choleroe toxins. These characteristics were identical to those of a toxin implicated in the aetiology of antibiotic-induced colitis in the hamster. One patient improved rapidly after treatment with oral vancomycin, and at the same time the toxin disappeared from the stool.
Also PCMA Working Paper #15.
We have conducted a multi-model intercomparison of cloud-water in five state-of-the-art AGCMs run for control and doubled carbon dioxide climates. The most notable feature of the differences between the control and doubled carbon dioxide climates is in the distribution of cloud-water in the mixed-phase temperature band. The difference is greatest at mid and high latitudes. We found that the amount of cloud ice in the mixed phase layer in the control climate largely determines how much the cloud-water distribution changes for the doubled carbon dioxide climate. Therefore evaluation of the cloud ice distribution by comparison with data is important for future climate sensitivity studies. Cloud ice and cloud liquid both decrease in the layer below the melting layer, but only cloud liquid increases in the mixed-phase layer. Although the de...
