Mutual neutralization in collisions of H+ with Cl.

The cross section and final state distribution for mutual neutralization in collisions of H+ with Cl- have been calculated using an ab initio quantum mechanical approach. It is based on potential energy curves and nonadiabatic coupling elements for the six lowest 1Σ+ states of HCl computed with the multireference configuration interaction method. The reaction is found to be driven by nonadiabatic interactions occurring at relatively small internuclear distances (R < 6 a0). Effects on the mutual neutralization cross section with respect to the asymptotic form of the potential energy curves, inclusion of closed channels, as well as isotopic substitution are investigated. The effect of spin-orbit interaction is investigated using a semiempirical model and found to be small. A simple two-state Landau-Zener calculation fails to predict the cross section

Reactions of C+ + Cl-, Br-, and I--A comparison of theory and experiment.

Rate constants for the reactions of C+ + Cl-, Br-, and I- were measured at 300 K using the variable electron and neutral density electron attachment mass spectrometry technique in a flowing afterglow Langmuir probe apparatus. Upper bounds of <10-8 cm3 s-1 were found for the reaction of C+ with Br- and I-, and a rate constant of 4.2 ± 1.1 × 10-9 cm3 s-1 was measured for the reaction with Cl-. The C+ + Cl- mutual neutralization reaction was studied theoretically from first principles, and a rate constant of 3.9 × 10-10 cm3 s-1, an order of magnitude smaller than experiment, was obtained with spin-orbit interactions included using a semiempirical model. The discrepancy between the measured and calculated rate constants could be explained by the fact that in the experiment, the total loss of C+ ions was measured, while the theoretical treatment did not include the associative ionization channel. The charge transfer was found to take place at small internuclear distances, and the spin-orbit interaction was found to have a minor effect on the rate constant

Autism Spectrum Disorders in preschool children: cognitive aspects and interventions

Aim: The overarching aims of this thesis were to (a) gain further insight into the developmental/cognitive aspects of autism spectrum disorders (ASD) in young children, and (b) assess outcome after interventions of varying intensity. Methods: In a prospectively designed longitudinal naturalistic study, 208 preschool children with ASD were comprehensively assessed - including with a variety of cognitive tests and other structured neurodevelopmental/adaptive interviews, observation schedules and questionnaires - before start of intervention and at the end of intervention after two years. Interventions given were based on principles of applied behaviour analysis (ABA) and were classified as intensive or non-intensive. The primary outcome variable was change in Vineland Adaptive Behavior Scales composite scores. Subgroups with Good outcome and Poor outcome were identified by ≥15% positive/negative change in VABS composite scores. Results: Considerable changes with regard to ASD type, general cognitive level, adaptive behaviour and expressive speech were found, especially in children with atypical autism and in those with developmental delay/borderline intellectual functioning at the first assessment. About half the total group met criteria for intellectual disability (ID) at the two-year follow-up. Adaptive behaviour levels corresponded well with the level of intellectual functioning. Low processing speed negatively affected general adaptive skills, including in the domains communication, daily living skills, and motor skills. There was no difference in outcome between the intensive and non-intensive intervention groups. The single most important outcome predictor was cognitive level when dichotomized into IQ70. Conclusions: Development profiles changed considerably in many children over the two-year period. Low processing speed - possibly indicative of executive dysfunction - was common even in relatively high functioning children. There was no significant difference between the intensive and non-intensive groups with regard to outcome; instead the child´s general cognitive level seemed to be the most important factor for prognosis. Children who are diagnosed with ASD at a very young age need to be followed up prospectively over several years. The naturalistic findings do not provide support for the use of very intensive as compared with less intensive ABA intervention in a community-based group of children with ASD

Children with autism spectrum disorders who do not develop phrase speech in the preschool years

There is uncertainty about the proportion of children with autism spectrum disorders who do not develop phrase speech during the preschool years. The main purpose of this study was to examine this ratio in a population-based community sample of children. The cohort consisted of 165 children (141 boys, 24 girls) with autism spectrum disorders aged 4–6 years followed longitudinally over 2 years during which time they had received intervention at a specialized autism center. In this study, data collected at the 2-year follow-up were used. Three categories of expressive language were defined: nonverbal, minimally verbal, and phrase speech. Data from the Vineland Adaptive Behavior Scales-II were used to classify expressive language. A secondary objective of the study was to analyze factors that might be linked to verbal ability, namely, child age, cognitive level, autism subtype and severity of core autism symptoms, developmental regression, epilepsy or other medical conditions, and intensity of intervention. The proportion of children who met the criteria for nonverbal, minimally verbal, and phrase speech were 15%, 10%, and 75%, respectively. The single most important factor linked to expressive language was the child’s cognitive level, and all children classified as being nonverbal or minimally verbal had intellectual disability

Preschoolers with Autism Spectrum Disorder followed for 2 years: those who gained and those who lost the most in terms of adaptive functioning outcome

Clinical predictors of 2-year outcome in preschoolers with ASD were studied in a population-based group of very young children with ASD (n = 208). Children who gained the most (n = 30) and lost the most (n = 23), i.e., increased or decreased their adaptive functioning outcome according to the Vineland Composite Score between study entry (T1) and follow-up (T2), 2 years later were compared. Individual factors that differed significantly between the two outcome groups were cognitive level, age at referral, not passing expected milestones at 18 months, autistic type behavior problems and regression. However, logistic regression analysis showed that only cognitive level at T1 (dichotomized into IQ < 70 and IQ ≥ 70) made a unique statistically significant contribution to outcome prediction (p = <.001) with an odds ratio of 18.01. The findings have significant clinical implications in terms of information at diagnosis regarding clinical prognosis in ASD