Cognitive assessment using the Rapid Assessment for Developmental Disabilities, Second Edition (RADD-2).

BACKGROUND: Individuals with developmental disabilities (DD) often have severe impairments and maladaptive behaviours that make it difficult to reliably assess their cognitive abilities. Given these challenges, the Rapid Assessment of Developmental Disabilities, Second Edition (RADD-2), was designed to measure general cognitive ability in this population. The purpose of this study is to demonstrate the battery's psychometric properties when used with individuals with DD who have challenging behavioural and psychiatric conditions and for those who have limited verbal skills. METHOD: The cognitive and adaptive behaviour skills of 193 children and adults with DD and considerable medical, behavioural and/or psychiatric problems were evaluated using the first and second editions of the RADD, Kaufmann Brief Intelligence Test - 2nd Edition, and Scales of Independent Behaviour - Revised Edition. Medication side effects and challenging behaviours were assessed using the Aberrant Behaviour Checklist. RESULTS: There were no floor or ceiling effects on the RADD-2. Both the nonverbal index and total scores had strong concurrent validity with other abbreviated tests of intellectual ability and good discriminant validity from measures of adaptive behaviour and medication side effects. RADD-2 scores also had strong criterion validity as they successfully differentiated between all levels of intellectual functioning. Age and sex did not differentially affect RADD-2 performance, and the co-occurrence of psychiatric conditions did not negatively affect performance. The only medical condition associated with lower RADD-2 performance was epilepsy. CONCLUSIONS: The RADD-2 can quantify the differential cognitive abilities of individuals with DD, even for those with minimal communication skills, challenging behaviours or severe medication side effects that can typically complicate assessment. This brief cognitive battery can be used to measure changes due to interventions, on the one hand, and progression of neurological disease, on the other.

The relationship between living arrangement and adherence to antiepileptic medications among individuals with developmental disabilities.

BACKGROUND: Non-adherence to antiepileptic drugs (AEDs) is associated with considerable morbidity and mortality in the general population but little is known about adherence in individuals with intellectual disability (ID). METHOD: Using the records of a closed pharmacy billing system over a 30 month period, we examined the medication non-adherence rates for AEDs among 793 individuals with ID. We calculated the medication possession ratio (number of days each participant was in possession of an AED), and defined non-adherence as 25% or more of the exposure days without the possession of an AED. All participants studied had filled prescriptions for AEDs spanning at least 6 months. RESULTS: Controlling for age and gender, we found non-adherence rates varied by living arrangement. Compared with those living in group homes, individuals with ID living in family homes or in semi-independent settings were significantly less adherent to AEDs (P < 0.0003). CONCLUSION: Non-adherence to AEDs is a potential medical risk for individuals with ID that is significantly impacted by the type of community living arrangement.

Modeling resonance tests for electrostrictive ceramics.

The electromechanical coupling coefficient represents a useful figure-of-merit for comparing the quality of different electroactive materials. However, the coupling coefficient for an electrostrictive ceramic is not a unique material parameter, because it depends strongly on the applied DC bias field, AC field amplitude and frequency, and stress. These dependencies make direct comparison between electrostrictors and piezoelectrics somewhat ambiguous. In this paper, we developed a pair of coupling parameters for electrostrictors that were strictly material constants and completely characterized the material's electromechanical quality. We proposed relatively simple, inexpensive resonance testing to measure these new parameters from the electrical admittance of a vibrating electrostrictive rod. The electromechanical coupling coefficient for a specific loading condition is computed from these parameters, allowing direct comparison between electrostrictive and piezoelectric materials.

A dynamics model for nonlinear electrostrictive actuators.

This paper examines the nonlinear vibration of an electrostrictive ceramic rod actuator excited by a harmonic voltage source. A frequency-domain model was developed using the nonlinear constitutive law for electrostriction. The results predict harmonic distortion of the device's displacement due to the ceramic's nonlinear behavior. AC voltage signal and DC voltage bias were studied to determine the optimum power source parameters for minimizing distortion. The calculations show that the rod's resonance frequency and amplitude depend on the electromechanical coupling strength and differ greatly for large AC voltages from the equivalent linear piezoelectric results. The nonlinear analysis relates the device's electromechanical coupling coefficient to the computed resonance and antiresonance frequencies. This important result could provide the basis for future measurement of the electrostrictive coupling coefficient using resonance techniques.

Pleiotropic stabilizing selection limits the number of polymorphic loci to at most the number of characters.

We demonstrate that, in a model incorporating weak Gaussian stabilizing selection on n additively determined characters, at most n loci are polymorphic at a stable equilibrium. The number of characters is defined to be the number of independent components in the Gaussian selection scheme. We also assume linkage equilibrium, and that either the number of loci is large enough that the phenotypic distribution in the population can be approximated as multivariate Gaussian or that selection is weak enough that the mean fitness of the population can be approximated using only the mean and the variance of the characters in the population. Our results appear to rule out antagonistic pleiotropy without epistasis as a major force in maintaining additive genetic variation in a uniform environment. However, they are consistent with the maintenance of variability by genotype-environment interaction if a trait in different environments corresponds to different characters and the number of different environments exceeds the number of polymorphic loci that affect the trait.

Control theory predictions of reproductive allocation in female dusky salamanders.

A model of the reproductive ecology of female dusky salamanders was used to investigate the allocation scheme that a female might use to maximize her reproductive success. Analysis of the model with techniques of optimal control theory suggests that fecundity is maximized either by allocating food resources to reproduction for the entire time period prior to egg laying, or by growing first, then switching to reproduction later in the year. The analysis also indicates that egg mortality will be minimized if the female provides maternal care at the maximum level throughout egg brooding. These results are not specific to dusky salamanders, but can be extended to other organisms with similar reproductive characteristics.