[German phoneme contrast hierarchy. A study with preschool children]. / Kontrasthierarchie deutscher Phoneme. Eine Untersuchung bei Vorschulkindern.

BACKGROUND: Phonemes are defined as the smallest possible units of speech with a distinctive function. Major and minor class features are used to describe individual phonemes. Phoneme opposition is based on distinctive feature contrasts. Here we constructed minimal pairs (MP) with different degrees of opposition. Preschool children were asked to repeat these MP after auditory presentation. We then investigated whether the phoneme contrast hierarchy corresponded to the empirically found degree of difficulty. METHODS: A total of 161 preschool children (96 boys, 65 girls) participated voluntarily. Real word MP (RW-MP) and nonsense word MP (L-MP) were presented from a CD recording via loudspeakers. MP were based on phonemes covering a wide range of phoneme oppositions. The children had to repeat the MP. Confusion errors were compared to the degree of phoneme opposition. RESULTS: A weak correlation was found between the theoretical degree of phoneme opposition and the phoneme confusion error matrix. When errors within an item block were added, no significant correlation was found. However, for MP with the least degree of opposition, confusion errors were always highest. DISCUSSION: The degree of markedness in MP influenced the correct perception/production of these MP. This influence must be regarded as fairly weak.

[Gender and phoneme discrimination ability]. / Ist die Lautdiskriminationsfähigkeit geschlechtsabhängig?

BACKGROUND: Boys tend to acquire language skills later than girls. Furthermore, specific language impairment and dyslexia are more often diagnosed in males than in females indicating that efficiency of phonological processing may be gender dependent. Phoneme discrimination tests tap some phonological processing abilities. Here we raised the question if phoneme discrimination abilities in male preschool children are inferior to female's phoneme discrimination abilities thus indicating less efficient phonological processing in boys. METHODS: Participants were 161 preschool children. Phoneme discrimination was tested using minimal pair (MP) reproduction. MP were either real words or nonwords (logatoms) presented in duplets or triplets. Children were asked to repeat what they had heard (immediate serial recall task). Statistical analyses were performed using Mann-Whitney-U-tests. RESULTS: Neither a correlation was seen between gender and phoneme discrimination sum scores (i. e. all items) nor between gender and scores of each item block. DISCUSSION: Results indicate no difference between male and female children in regard to those phonological processes and representations being tapped by the test procedure employed here.

[Phonological loop and minimal pair discrimination in preschool children]. / Hörmerkspanne und Minimalpaardiskrimination bei Vorschulkindern.

BACKGROUND: Phoneme discrimination tests based on presenting minimal pairs (MP) are frequently used to assess auditory processing. However test results may be influenced by other factors beside proper acoustic representation. Here we aim at determining whether working memory capacity (WMC) correlates with reproducing sets of MP. METHODS: WMC was evaluated by memory span for digits in 161 preschool children. MP were either real words or non-words (logatoms). Both real word-MP and logatom-MP were presented in duplets or triplets. Children were asked to repeat what they had heard. Spearman rank correlation was used to analyse the data. RESULTS: All four test item blocks showed a significant positive correlation with WMC (group values). Some children with poor WMC performed sufficiently on MP discrimination and vice versa. DISCUSSION: Besides confirming the phonological similarity effect, our data indicates a significant interdependence between different processes and phonological representations. This must be taken into account when using MP tests for evaluating "auditory processing" in the clinical routine. However, poor WMC is neither necessary nor obligatory for poor phoneme discrimination.

Liposome-mediated enhancement of the sensitivity in immunoassays of proteins and peptides in surface plasmon resonance spectrometry.

A recently developed liposome sandwich immunoassay for interferon-gamma (IFN-gamma), to be applied in microtiter plates, is tailored for surface plasmon resonance (SPR) spectrometry. The assay is performed on a thin (approximately 20 nm) polystyrene layer that covers a gold surface. This way, analytical data obtained from microtiter plate technology can directly be extrapolated toward SPR. For assaying the antigen IFN-gamma, a 16-kDa cytokine, a capture monoclonal antibody is physically adsorbed onto the polystyrene surface. After addition of the sample containing IFN-gamma, a biotinylated detecting antibody is added. Avidin is used as a bridging molecule between the biotinylated antibody and the biotinylated liposomes. All solutions are prepared with PBS buffer (10 mM, pH 7.4). This avoids additional changes in index of refraction caused by the use of various buffer solutions in immunoassays on microtiter plates for coating, binding, and washing procedures. It is shown that, when liposomes are used, a substantial enhancement of the detection limit is achieved. The "liposome" strategy improves the sensitivity for the IFN-gamma assay approximately 4 x 10(4) times and the detection limit to low picomolar. The method is generally applicable to other sandwich immunoassays.

Self-assembled monolayers for biosensors.

The use of self-assembled monolayers (SAMs) in various fields of research is rapidly growing. In particular, many biomedical fields apply SAMs as an interface-layer between a metal surface and a solution or vapour. This review summarises methods for the formation of SAMs upon the most commonly used materials and techniques used for monolayer characterisation. Emphasis will lie on uniform, mixed and functionalised monolayers applied for immobilisation of biological components including (oligo-)nucleotides, proteins, antibodies and receptors as well as polymers. The application of SAMs in today's research, together with some applications will be discussed.