Convexity
Mostrando 37-48 de 55 artigos, teses e dissertações.
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37. Mathematical theory of group selection: Structure of group selection in founder populations determined from convexity of the extinction operator*
Genetic analysis for group selection is developed for the case of a biallelic locus (A, a) undergoing group selection of founder populations only. By contrast to R. Levins“E = E(x) models, extinction now depends on genetics at the propagule stage but acts uniformly on larger populations. Biological evidence supports this hypothesis, which also allows mathe
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38. Aspects of interhemispheric subdural haematoma, including the falx syndrome.
Two cases of interhemispheric subdural haematoma are reported. The first patient presented with a falx syndrome of contralateral hemiparesis, most marked in the lower extremity. The second patient had vertex headaches and was diagnosed with computerised tomography. Serial studies suggested that the interhemispheric haematoma may have migrated to a lateral po
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39. An optimal multiple decision rule for signs of parameters
The problem of simultaneously deciding the signs of p parameters based on normally distributed estimators is considered. A decision that a parameter is too close to zero to decide its sign is allowed in order that the probability of at least one incorrect decision can be kept less than a preassigned value. Concepts of upper-convexity and local optimality are
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40. Convexity properties of products of random nonnegative matrices
Consider a sequence of N × N random nonnegative matrices in which each element depends on a vector u of parameters. The nth partial product is the random matrix formed by multiplying, from right to left, the first n of these random matrices in order. Under certain conditions, the elements of the nth partial product grow asymptotically exponentially as n inc
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41. Treatment of congenital aneurysms of the left atrium and left atrial appendage.
We report 2 cases of congenital aneurysm, 1 of the left atrium and 1 of the left atrial appendage. The patients were 14 and 27 years of age, respectively. Their common symptoms were paroxysmal palpitations and dyspnea. Diagnoses were suggested by chest radiographic films that revealed prominent convexity at the upper left border of the heart and were confirm
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42. Atrial infarction leading to rupture.
In the case described, necrosis of the atrial musculature led to rupture of the chamber. This was overlooked for 4 days until the patient died of ventricular rupture. This unusual complication of atrial infarction may be amenable to surgical repair if recognised in time. The high gain recording of P waves in the presence of AV block made it possible to evalu
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43. Supratentorial extracerebral cysts in infants and children.
Twelve cases of supratentorial extracerebral cysts in infants and children are reported. Eight were located in the Sylvian fissure, two in the interhemispheric fissue, and two over the convexity of the cerebral hemispheres. Irrespective of their precise location these cysts, in their common, uncomplicated form, give rise to a clinical syndrome different from
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44. Migration of craniofacial periosteum in guinea-pigs with unilateral masticatory muscle paralysis.
The amount and direction of movement of the fibrous periosteum of the nasal, frontal, and parietal bones in the guinea-pig have been documented after experimentally induced unilateral paralysis of the masticatory muscles. Marked craniofacial asymmetries and muscle atrophy were observed after electrolytic lesions of the trigeminal motor nucleus were made. The
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45. Visual habit formation in monkeys with neurotoxic lesions of the ventrocaudal neostriatum
Visual habit formation in monkeys, assessed by concurrent visual discrimination learning with 24-h intertrial intervals (ITI), was found earlier to be impaired by removal of the inferior temporal visual area (TE) but not by removal of either the medial temporal lobe or inferior prefrontal convexity, two of TE's major projection targets. To assess the ro
The National Academy of Sciences.
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46. Central-peripheral transitional zone of the spinal accessory nerve in the rat.
The spinal accessory nerve rootlets emerge from the lateral aspect of the upper five segments of the cervical spinal cord underlying the nerve trunk. They cross the lateral funiculus of the cord with a slight rostral inclination. Here some pursue a relatively straight course while others have a dorsal convexity. The transitional zones may be classified into
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47. Prognostic value of the amount of post-traumatic subarachnoid haemorrhage in a six month follow up period.
Clinical and radiological patterns from 148 patients with post-traumatic subarachnoid haemorrhage (TSAH) were analysed with specific regard for the amount and distribution of blood in subarachnoid spaces to verify if these variables have any influence on overall outcome. The degree and extent of TSAH were classified according to Fisher's criteria: in 93 pati
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48. Aspartic acid aminotransferase activity is increased in actively spiking compared with non-spiking human epileptic cortex.
Increased concentration of the excitatory neurotransmitter aspartic acid in actively spiking human epileptic cerebral cortex was recently described. In order to further characterise changes in the aspartergic system in epileptic brain, the behaviour of aspartic acid aminotransferase (AAT), a key enzyme involved in aspartic acid metabolism has now been examin