Experimental breakdown of selected anodized aluminum samples in dilute plasmas

Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples

Leaf area index of boreal forests: theory, techniques, and measurements

Leaf are index is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LAI estimates are required in studies of ecophysiology, atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LAI values obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal Ecosystem Atmosphere study

The Specificity of Inhibitory Impairments in Autism and Their Relation to ADHD-Type Symptoms

Findings on inhibitory control in autism have been inconsistent. This is perhaps a reflection of the different tasks that have been used. Children with autism (CWA) and typically developing controls, matched for verbal and non-verbal mental age, completed three tasks of inhibition, each representing different inhibitory subcomponents: Go/No-Go (delay inhibition), Dog-Pig Stroop (conflict inhibition), and a Flanker task (resistance to distractor inhibition). Behavioural ratings of inattention and hyperactivity/impulsivity were also obtained, as a possible source of heterogeneity in inhibitory ability. CWA were only impaired on the conflict inhibition task, suggesting that inhibitory difficulty is not a core executive deficit in autism. Symptoms of inattention were related to conflict task performance, and thus may be an important predictor of inhibitory heterogeneity