Electroencephalographic and rheoencephalographic studies of cerebral meningovascular tumors

For forty-one meningovascular tumors, which were verified pathologically and anatomically, the authors tried to find electroencephalographic and rheoencephalographic criteria of the recognition of the location and particular kind of tumor. Electroencephalographic results obtained for meningovascular tumors are characterized by insignificant to moderate general and focal alterations. The results of rheoencephalographic examinations were found to add to the possibilities of topical diagnosis. Angioarchitectural characteristics of the rheoencephalographic curve, together with bioelectric phenomena, enabled a specific diagnosis to be established for twenty-four of the meningovascular tumors.     

Changes of the visual field with cerebral tumors]

Neurosurgical material of 1,746 tumours is reviewed for the relations between operative and post mortem localization of cerebral tumours and pathological findings of isopteric perimetry; and the incidence of defects of the visual field with the different localizations of tumours is discussed. The aim was to localize the tumours as accurately as possible. At least in brain tumour patients the defect of the visual field does not allow conclusions on the level of lesions to the visual pathway. Only the superior quadranopsia is important for the temporal localization.     

Retention of orienting reaction habituation in patients with epileptogenic cerebral tumors

An electrographic study on habituation of the somatic (EMG), autonomic (finger plethysmogram, galvanic skin reaction, respiration, pulse) and EEG (acoustic evoked potential and EEG-blocking reaction) components of the orienting reaction elicited by a repetitive auditory stimulus during successive (weekly) sessions was performed in 41 patients with epileptogenic cerebral tumors (ECT) and in 128 control subjects. The study evidenced significant retention disturbances of orienting reaction habituation (i.e., of learning), the “saving” of stimulations, achieved from one session to the other to obtain the habituation criterion, being lesser in ECT patients than in control subjects. The severity of habituation retention disturbances depended on the tumor site and size, as well as on the electro-clinical form and frequency of seizures. Thus, the most marked habituation retention disturbances were found in patients with temporal or predominantly temporal epileptogenic tumors, in cases with large hemispheric epileptogenic tumors (over 6 cm), in patients with generalized or generalized plus partial seizures, as well as in those with frequent (daily) seizures.     

Changes of visual fields in intracranial tumors outside the cerebral hemispheres]

Based on neurosurgical material of 1,746 brain tumours, the changes of the visual field determined by isopteric perimetry are discussed with their significe with regard to tumours of corpus callosum, lateral ventricles, brain stem ganglia, IIIrd ventricle, region of the sella and adjacent areas as well as posterior fossa. The proportion of unilateral blindness with primary opticus atrophy and of skotomas is strinkingly high, so that in cases of loss of vision, not readily explicable by ophthalmology, as well as in unilateral defects of the visual field, intracranial processes must be thought of.     

Results of cerebral computer tomography in the diagnosis of tumors of the sella region

Computer tomography (CT) is an important aid to the diagnosis of sella tumours because it images the tumour directly and delineates it from the healthy tissues. The tumour type can be identified to a certain extent, but angiography is necessary to distinguish tumours from aneurysms. The study is based on 140 surgical and histological examinations, the results of which were compared wit those obtained by CT. Suprasellar inflammations could always be identified by CT. Although intrasellar tumours may be identifiable by CT if full use is made of the potential of the equipment, negative CT results do not necessarily mean that there is no tumour. The diagnostic validity of the method is restricted by the absence of "standards", against which the variable images of intrasellar structures can be judged, and the restricted resolution of CT.     

On fineness of grain

A central job for propositions is to be the objects of the attitudes. Propositions are the things we doubt, believe and suppose. Some philosophers have thought that propositions are sets of possible worlds. But many have become convinced that such an account individuates propositions too coarsely. This raises the question of how finely propositions should be individuated. An account of how finely propositions should be individuated on which they are individuated very finely is sketched. Objections to the effect that the account individuates propositions too finely are raised and responses to the objections are provided. It is also shown that theories that try to individuate propositions less finely have serious problems.     

Dynamic balance between grain refinement and grain growth during high-pressure torsion of Cu powders

High-pressure torsion (HPT) was applied to unmilled coarse-grained (CG) Cu powders with low initial dislocation density and cryomilled nanocrystalline (nc) Cu powders with high initial dislocation density, with identical processing parameters. HPT of unmilled CG Cu powders resulted in exceptional grain refinement and increase in dislocation density, whereas significant grain growth and decrease in dislocation density occurred during HPT of cryomilled nc Cu powders. Equilibrium structures were achieved under both conditions, with very similar stable grain sizes and dislocation densities, suggesting dynamic balances between deformation-induced grain refinement and grain growth, and between deformation-induced dislocation accumulation and dislocation annihilation. The equilibrium structures are governed by these two dynamic balances.     

Fracture mechanisms of symmetrical tilt grain boundaries

The mechanisms of failure of symmetrical tilt boundaries have been investigated using an atomistic technique. The fracture process advances in steps that are related to the structural unit of the symmetrical tilt grain boundary. These boundaries are shown to fail through a combined mechanism involving dislocation emission in certain regions of the structural unit, followed by microcleavage, and again dislocation emission. The overall toughness of the boundaries is given by the combination of the toughness of these two processes.     

Strategic regulation of grain size in memory reporting

To increase their report accuracy, rememberers may either withhold information that they feel unsure about or provide relatively coarse information that is unlikely to be wrong. In previous work (A. Koriat & M. Goldsmith, 1996c), the authors delineated the metacognitive monitoring and control processes underlying the decision to volunteer or withhold particular items of information (report option) and examined how these processes are used in the strategic regulation of memory accuracy. This article adapts that framework to address control over the grain size (precision-coarseness) of the information that people report. Results show that rememberers strategically regulate the grain of their answers to accommodate the competing goals of accuracy and informativeness. The metacognitive processes underlying this regulation are elucidated.     

On the structural unit model of grain boundary structure

Abstract

A critique of the structural unit model is presented. It is shown that the predictive capacity of the model is severely limited when it is applied to boundaries with relatively-high-index rotation axes. Recent computer simulations suggest that ‘high index’ means 〈221〉 and above. A new approach to grain boundary structure is needed for mixed tilt and twist boundaries.     

Pinning of grain boundary migration by a coherent particle

We studied single-particle pinning of grain boundary (GB) migration during grain growth. A phase-field model was formulated to simulate the pinning by a coherent particle and validated quantitatively by comparison with analytical prediction. A study of GB migration velocity using this model revealed that second-phase coherent particles have a previously unknown restraining effect over the whole of the GB-particle interaction range, which is qualitatively different from the interaction between GB and incoherent particles.     

Nanoindentation creep behavior of grain boundary in pure magnesium

Nanoindentation creep tests were performed at the grain boundary and grain interior in pure magnesium. The grain boundary showed a high strain rate sensitivity exponent and was dominated by grain boundary sliding due to the high diffusion rate at the grain boundary. The grain boundary affected the deformation behavior of the area at a distance of 2 µm into the grain interior. On the other hand, the grain interior had a low strain rate sensitivity exponent, because its matrix was too large to be influenced by the grain boundary. The deformation mechanism in the grain interior was determined to be dislocation slip.     

Patterns of cerebral organization

An analysis of the concurrent incidence of aphasia and spatial disorder in 270 patients with unilateral brain damage suggests that the two functions are statistically independent. These data can also be used to estimate the distribution of left, right, and bilateral representation of linguistic and spatial functions in the population. In right-handers, sex affects the pattern of cerebral asymmetries, while the familial history of sinistrality has a stronger effect on the pattern of cerebral asymmetries in left-handers. These findings suggest that complementary specialization exists only as a statistical norm: It is suggested that differences in complementary and noncomplementary specialization may underlie individual differences in cognitive skills.