Submicrometer metallic barcodes.

We synthesized multimetal microrods intrinsically encoded with submicrometer stripes. Complex striping patterns are readily prepared by sequential electrochemical deposition of metal ions into templates with uniformly sized pores. The differential reflectivity of adjacent stripes enables identification of the striping patterns by conventional light microscopy. This readout mechanism does not interfere with the use of fluorescence for detection of analytes bound to particles by affinity capture, as demonstrated by DNA and protein bioassays.

Model simulations of spatial distributions and daily totals of photosynthesis in Eucalyptus grandis canopies.

A simulation model for radiation absorption and photosynthesis was used to test the hypothesis that observed nonuniform distributions of nitrogen concentrations in young Eucalyptus grandis trees result in greater amounts of daily assimilation than in hypothetical trees with uniform N distributions. Simulations were performed for trees aged 6, 9, 12 and 16 months which had been grown in plantations under a factorial combination of two levels of fertilization and irrigation. Observed leaf N distribution patterns yielded daily assimilation rates which were only marginally greater (<5%) than for hypothetical trees with uniform distributions. Patterns of assimilation distribution in individual tree crowns closely resembled those for absorbed radiation, rather than for N. These conclusions were unaffected by three choices of alternative leaf area density distributions. The simulation model was also used to calculate hourly and daily rates of canopy assimilation to investigate the relative importance of radiation absorption and total canopy nitrogen on assimilation. Simulated hourly rates of carbon assimilation were often lightsaturated, whereas daily carbon gain was directly proportional to radiation absorbed by the tree crown and to total mass of N in the leaves. Leaf nitrogen concentrations determined photosynthetic capacity, whereas total leaf area determined the amount of radiation absorbed and thus the degree to which capacity was realized. Observed total leaf area and total crown N were closely correlated. The model predicted that nitrogen use efficiences (NUE, mol CO2 mol-1 N) were 60% higher for unfertilized than for fertilized trees at low levels of absorbed photosynthetically active radiation (PAR). Nitrogen use efficiency was dependent on fertilizer treatment and on the amount of absorbed PAR; NUE declined with increasing absorbed PAR, but decreased more rapidly for unfertilized than for fertilized trees. Annual primary productivity was linearly related to both radiation absorbed and to mass of N in the canopy.

Spatial distributions of foliar nitrogen and phosphorus in crowns of Eucalyptus grandis.

Eucalyptus grandis trees were grown in plantations with and without added fertiliser to examine the effects of plant nutrition on photosynthesis and growth. Leaves were sampled from known locations within canopies of selected trees and leaf N and P concentrations were measured. Contour maps of N and P distributions were then produced for crowns of trees aged between 6 and 16 months. Gas exchange measurements on sample leaves were used to estimate parameters of a model of C3 photosynthesis as a function of leaf N and P contentrations. Linear relationships were obtained between model parameters and leaf N concentration, but P appeared to be present in excess, since no correlation was found with P contentration. Photosynthetic light response curves were calculated for model leaves with differing N concentrations. The curves show that optimal concentrations of N in leaves depend on mean levels of irradiance during growth.

Word knowledge acquisition in retarded children: a longitudinal study of acquisition of a complex linguistic structure.

The purpose of this 1-year longitudinal study was to investigate the acquisition of word knowledge by 18 retarded children. The words examined were relevant to the correct interpretation of sentences of the type "John is eager/easy to please." The interest was in how retarded children acquire the subcategorization features of these words. The study revealed that retarded children, like intellectually normal children, show great inconsistencies in their interpretations of specific words during an intermediate stage of performance on this linguistic structure; but the errors by retarded children, in contrast to those by intellectually normal children, were highly correlated with word frequency. The results are interpreted in representations. Interpretations based on gradual acquisition of word knowledge are contrasted with a reorganization theory, and a synthesis of the two views is given. Possible explanations for the finding that the retarded children nevertheless differed from intellectually normal children in the relation of their errors to word frequency are also given.

Language growth with experience without feedback.

The relationship between language input and the precise way the child makes use of that input is a complex problem. Most research has concentrated on specific forms in the input and their later production by the child. It may be, however, that the child controls more of the acquisition process than previous input studies have assumed. Experience of particular language forms may be all that is required for internal organizational processes to operate. This longitudinal study investigated language growth in children using a structure they had not yet mastered. Experience of this structure at 3-month intervals over the course of 1 year--without any feedback that children were interpreting some instances incorrectly--led to accelerated acquisition as compared with the ages observed in children tested cross-sectionally. It is argued that exposure to a linguistic structure that induces the child to operate on that structure can lead to a reorganization of linguistic knowledge even though no direct feedback has been given as to its correct adult interpretation.

Hierarchical planning disability in the drawings and constructions of a special group of severely aphasic children.

A small group of severely receptive aphasic children who appear to be suffering from a rare aphasic syndrome that has been referred to in the literature as "acquired aphasia with convulsive disorder in children" was tested on drawing and construction tasks which tap hierarchical planning abilities. Although they could draw and construct a complex figure when using a serial method, they could not do so when required to use hierarchical planning in building up the model in terms of its subunits. Their scores reflecting hierarchical ability were significantly lower than those of age-matched profoundly deaf and normal children. The nature of this disability is discussed and its effects noted on tasks in other modalities. It is argued that neither an auditory deficit theory nor a short-term memory deficit theory is adequate to account for the observed disabilities. Individual differences in the group were noted. It was also found that a smaller percentage of developmentally expressive aphasic children evidenced the hierarchical planning disability. It is concluded that a primary hierarchical planning disability in some aphasic children can account for some aspects of their linguistic disabilities and for disabilities on other nonlanguage and nonauditory tasks.

Developmental language disorders: cognitive processes, semantics, pragmatics, phonology, and syntax.

Five areas of research concerned with language acquisition--cognitive processes, semantics, pragmatics, phonology, and syntax--are reviewed in terms of their contribution to understanding language disorders. Two views of cognitive processes are discussed. One of these, emphasizing cognitive mechanisms such as short-term memory, is seen as providing possible explanations for some types of language deficits. The other, a concern with conceptual knowledge, is subjected to a critical analysis questioning how complete an explanation it is able to offer for some aspects of language acquisition. Problems of definition are also discussed when semantic aspects of language are considered. Problems in the pragmatic component of language are seen as providing an explanation for particular aspects of language disorder in some autistic children. The importance of focusing on phonology as a central grammatical process is discussed and linked to dyslexia and to spelling disorders. Finally, it is argued that the acquisition of syntactic structure is not yet understood. Impairments such as a hierarchical planning order deficit may affect syntactic ability and lead to disordered language, as found in some types of developmentally aphasic children. It is concluded that it is important to study all five areas of the title, and their interrelationships, if various language disorders are to be adequately understood.

Children's perceptual organization of seriated displays: evidence against a memory reorganization hypothesis.

The memory for a seriated display and its reorganization over an eight-month interval was examined in educationally subnormal children. By including groups of children who viewed a random display and an array of disordered sticks, it was found that the reorganization into a more seriated drawing after the passage of time was not directly based on the original stimulus. Various controls including copying of the original material, and matching and recognition conditions, give evidence that the child's cognitive level affects encoding of the material as well as its later output. The observed phenomenon of 'memory' improvement may have little to do with stored images, and may instead be linked to the developmental symbolic level of the child which influences original perception as well as 'memory'. It was also found that educationally subnormal children perform like normal children of the same mental age on the seriation task.