RESUMEN
Much capillary electrochromatography (CEC) work is carried out on bonded silica packings which offer many advantages: the number of such packings which are available; the fact that the chemistry of bonding and the separation process are fairly well understood; and the possibility of the transfer to CEC of existing HPLC methods. Packing methods for the preparation of CEC columns have been investigated. The problems inherent in the use of burned-in frits remains an obstacle, but can be at least partially overcome by minimising the length and by silanisation. The influence of a variety of mobile phase variables on aspects of CEC is in agreement with theory for: ionic strength, organic content (including isoeluotropy), and pH. Temperature can be used as a variable to change column selectivity in CEC. The influence of pH on electroosmotic flow (EOF) by changing the degree of ionisation of residual silanol groups is similar for a wide range of neutral bonded groups, but is much less marked for bonded sulphonic acid groups. The EOF may be reversed for bonded groups containing nitrogen.
Asunto(s)
Cromatografía Capilar Electrocinética Micelar/métodos , Cromatografía Capilar Electrocinética Micelar/instrumentación , Tamaño de la Partícula , TemperaturaRESUMEN
This paper presents results from a study of task performance on a variety of spatial tasks in 9-11 year-old children with Turner's Syndrome (T.S.), divided into those with genotype 45XO and those with Mixed genotypes, including isochromosomes of X and mosaicism. There was a significant overall effect of group reflecting impaired spatial cognition in T.S. with greater decrement in the 45XO group. Further investigation of the significant group by task interaction indicated that the group effects appeared on a visuo-perceptual task and on three visuo-constructional tasks but that there were no specific deficits in the T.S. groups on visuo-spatial or tactile-spatial tasks. In T.S., visuo-perceptual and visuo-constructive sub-systems of spatial skill may be more vulnerable than other components of spatial cognition, to the neuro-biological influences which contribute to the disorder. Such dissociation supports theories of modularity in the development of spatial skill. The spatial tasks which create difficulty overlap only partially with those for which there are sex differences amongst normal children and do not represent a simple exaggeration of normal male-female differences.
Asunto(s)
Percepción Espacial/fisiología , Síndrome de Turner/diagnóstico , Niño , Desarrollo Infantil/fisiología , Cognición , Femenino , Lateralidad Funcional/fisiología , Genotipo , Humanos , Cariotipificación , Mosaicismo , Pruebas Neuropsicológicas , Factores Sexuales , Análisis y Desempeño de Tareas , Tacto/fisiología , Síndrome de Turner/genética , Síndrome de Turner/fisiopatología , Percepción Visual/fisiologíaRESUMEN
This study reports the results of 19 girls with Turner syndrome (TS), aged between nine and 12 years, in relation to intellectual profile and genotypic variation. The results were consistent with the notion that the behavioural phenotype of mixed TS involving predominantly mosaic karyotypes is less deviant from the normal pattern than that of pure 45XO. The results for the pure TS girls were consistent with an exaggeration of a normal sex difference, but for mixed TS girls this effect was task-dependent. There was no evidence of generalised deficiency or immaturity, and the task-specific effects support modularity in the development of components of cognitive skill and spatial ability. They also support a specific overall intellectual profile in TS, but with considerable inter-individual variation in its expression.