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Concentration Problems (concentration + problem)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Stress concentration factors of a general triaxial ellipsoidal cavity

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2008
CHUN-RON CHIANG
ABSTRACT The equivalent inclusion method is applied to solve the stress concentration problem concerning the disturbing effect of a general triaxial ellipsoidal cavity on an otherwise uniform normal stress state. Several useful solutions in simple form for limiting cases are derived and numerical results for general cases are obtained. These findings show the general features of the stress concentration factors around the base equator of the cavity. It is found that (1) when Poisson's ratio of the material is zero, the stress concentration factor does not vary along the equator of the cavity; (2) When the aspect ratio c/b of the cavity is very small, the stress concentration factor is also constant along the equator; (3) In general, the variation of stress concentration factors around the equator is less than 0.17 regardless of Poisson's ratio of the material. Thus, it is concluded that the stress concentration factor may be treated as constant around the equator of an ellipsoidal cavity with only a slight error. [source]

Exposure, health complaints and cognitive performance among employees of an MRI scanners manufacturing department

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2006
Frank de Vocht MSc
Abstract Purpose To assess sensory effects and other health complaints that are reported by system testers working near magnetic resonance imaging (MRI) magnets, realizing that it is believed that exposure up to 8 T is safe for humans. Materials and Methods Levels of exposure to static magnetic fields (SMFs), movement speed during exposure, health complaints, and cognitive performance among employees in an MRI-manufacturing department and at a reference department have been analyzed. Mercury concentrations in urine samples were determined to analyze whether they depend on exposure to SMFs. Results Average exposure of system testers was 25.9 mT/8 hours at a 1.0-T system and 40.4 mT/8 hours at a 1.5-T system. Vertigo, metallic taste, and concentration problems were more reported among workers of MRI-fabrication than in the reference department. Cognitive performance was tested outside the SMF, and no significant changes were detected. Conclusion This study suggests that any effects on cognitive functions are acute and transient and disappear rapidly after exposure has ended. All complaints, except for headaches, were more frequently reported by "fast movers" than by "slow movers," and depended on field strength and duration of exposure. Mercury-levels in urine were not affected. J. Magn. Reson. Imaging 2006. © 2005 Wiley-Liss, Inc. [source]

Diaschisis after thalamic stroke: a comparison of metabolic and structural changes in a patient with amnesic syndrome

ACTA NEUROLOGICA SCANDINAVICA, Issue 2007
V. Stenset
Introduction,, We present a patient with a left anteromedial thalamic lesion with an amnesic syndrome. The patient underwent neuropsychological testing, cerebrospinal fluid (CSF) analyses, magnetic resonance imaging (MRI) [T2, flair, and diffusion tensor imaging (DTI)] and [18F]-2-fluoro-deoxy- d -glucose positron emission tomography (FDG-PET) to assess indirect effects of thalamic lesions on cortical function. Case report,, A 67-year-old right-handed woman was admitted to a university-based memory unit because of memory and concentration problems. Neuropsychological testing revealed dysfunction of episodic memory, semantic memory and working memory. General intellectual function and attention capacity were preserved. MRI revealed an anteromedial thalamic lesion in the left hemisphere. FDG-PET showed decreased uptake in the frontal, parietal and temporal lobes of the left hemisphere. Regions of interest (ROI) in white matter were selected and left and right hemispheres were compared. Fractional anisotropy (FA) in ROI representing thalamo-cortical connections were decreased in the left hemisphere when compared with the right. Conclusion,, The results show the importance of a network that include the anterior and dorsomedian nuclei, which influence the activity in areas of the cortex responsible for memory processes. The imaging findings suggest that areas of cortical diaschisis after thalamic infarction correspond to areas affected by thalamo-cortical fibre loss as measured with FA. [source]

Behavioural, developmental and child protection outcomes following exposure to Class A drugs in pregnancy

CHILD: CARE, HEALTH AND DEVELOPMENT, Issue 1 2008
J. Topley
Abstract Background The long-term consequences of intrauterine exposure to Class A drugs are still relatively undocumented, and much of the literature relates to the North American experience, where cocaine use predominates. In Britain, heroin and amphetamine use is more common and, within Britain, patterns of drug use vary. Clearly the long-term educational and welfare needs of these children will be enhanced if the behavioural, developmental and child-care outcomes are known. This study attempts to explore some of these issues. Methods The developmental, behavioural and child protection outcomes in a group of 62 children exposed to Class A drugs in utero were investigated when the children were in full-time schooling. Results Seventy-four per cent (46/62) of the children at the time of the study had no educational or behavioural problems, and 11 (17.7%) were receiving extra support in school. No child had a statement of special educational need. Twelve (19.3%) were reported to have behaviour and concentration problems, and in four cases, this was attributed to poor-quality parenting at the time of the study. Three of the 12 children had fetal alcohol syndrome. Twenty-six (42%) children were placed on the Child Protection Register, and care orders or residence orders were granted for 22 (35.5%) of those who were placed on the register. All of the 22 children went into substitute care at some stage. Of these children, nine were adopted and 10 were placed permanently with other family members. Ten of the 62 (16.1%) children at the time of the study were of concern to professionals for child protection reasons, and four of them were on the Child Protection Register. Conclusions This study suggests we can be reasonably optimistic about the developmental and behavioural outcomes for children exposed to Class A drugs in utero. Over 50% required an intervention by social services, and 31% were in substitute care at the time of the study. There were continuing child protection concerns in 16% at school entry. [source]