Effect of maternal depression on infant-directed speech to prelinguistic infants: Implications for language development

The nature and timing of caregivers' speech provides an important foundation for infant attention and language development in the first year of life. Infant-directed speech is a key component of responsive parent-infant communication that is typically characterised by exaggerated intonation and positive affect. This study examines the effect of postnatal depression on the expression of positive vocal affect and pitch, the quantity of mothers' infant-directed speech input and the timing of vocal responses between mother and infant. Postnatal mothers currently experiencing symptoms of depression (n = 13) were matched to postnatal mothers who were not experiencing symptoms of depression (n = 13), and audio-recorded while playing with their 6-month-old infants. Compared with depressed mothers, non-depressed mothers used a higher mean pitch and pitch range, spoke more, gave faster verbal responses and were rated as expressing more positive valence in their voice. These preliminary findings indicate that mothers experiencing low mood use less infant-directed speech and less exaggerated pitch with prelinguistic infants. Postnatal depression is a major health issue that adversely impacts the parent and child. Early interventions for PND may benefit from identifying ways to support the timing of conversations and mothers' use of appropriate vocal pitch and infant-directed speech modifications. Further research is needed to confirm whether these strategies support early conversations

A qualitative investigation of consumer experiences of the child directed interaction phase of parent–child interaction therapy with toddlers

Background: Parent–child interaction therapy with toddlers (PCIT-T) is an adaptation of standard PCIT, developed to treat young children (12–24 months) with disruptive behaviours. The aim of this study was to gather preliminary qualitative data to gauge parental perceptions about the program. Methods: Semi-structured interviews were conducted with five parents who received the first phase of the program, ‘child directed interaction-Toddler’ (CDI-T) at a community based child behaviour treatment clinic. Interview transcripts were analysed thematically. Results: Participants were initially motivated to seek treatment because of concerns about and difficulties managing child behaviour. All participants reported a range of positive gains as a result of CDI-T including new parenting strategies, improved parental confidence and improved parent–child relationship quality. Live coaching from behind the one-way mirror, the relationship with the therapist and the home-based practice of skills between sessions were identified as important treatment components. Many participants spoke, however, about the difficulties they experienced with continuing to implement the home practice after program completion. Conclusions: Results suggest that CDI-T is perceived positively by consumers, and highlight a number of key program components

Qualitative evaluation of Australian Caregiver's experiences of parent–child interaction therapy delivered in a community-based clinic setting

Background: Parent–child interaction therapy (PCIT) is a short-term, evidence-based parent training program for parents of children aged 2–7 years with disruptive behaviour disorders (DBDs). The evidence-base for the effectiveness of PCIT is extensive but to date most studies have been quantitative in nature and conducted in university research clinics within the United States. Thus, understanding of the effectiveness and acceptability of PCIT in community-based settings in other countries, including Australia, is limited. Objective: This study used a qualitative methodology to explore Australian caregiver's perceptions of a standard PCIT program delivered at a community-based PCIT clinic. Method: Participants were nine mothers and one father who completed the PCIT program at the clinic for treatment of child DBD. Results: Thematic analysis yielded four major themes, namely “Parenting challenges before PCIT”; “Positive treatment outcomes” (sub-themes: improved child behaviour, increased parental confidence, increased insight into the child needs, and improved relationships with partner); “Program strengths” (sub-themes: child-directed interaction, parent-directed interaction, home practice, therapeutic relationship); and “Challenges experienced.”. Conclusions: These findings highlight the benefits of the PCIT program for families who are struggling with DBD in early childhood, and point to the potential positive impacts of disseminating PCIT within clinical settings more widely across Australia

Supersymmetric transformations for coupled channels with threshold differences

The asymptotic behaviour of the superpotential of general SUSY transformations for a coupled-channel Hamiltonian with different thresholds is analyzed. It is shown that asymptotically the superpotential can tend to a diagonal matrix with an arbitrary number of positive and negative entries depending on the choice of the factorization solution. The transformation of the Jost matrix is generalized to "non-conservative" SUSY transformations introduced in Sparenberg et al (2006 J. Phys. A: Math. Gen. 39 L639). Applied to the zero initial potential the method permits to construct superpartners with a nontrivially coupled Jost-matrix. Illustrations are given for two- and three-channel cases.Comment: 17 pages, 3 explicit examples and figures adde

Effects of crack tip geometry on dislocation emission and cleavage: A possible path to enhanced ductility

We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughness of the material by several orders of magnitude. We thus propose an atomic-scale mechanism at the crack tip, that ultimately may lead to a high fracture toughness in some materials where a sharp crack would seem to be able to propagate in a brittle manner. Results for blunt cracks loaded in mode II are also presented.Comment: 12 pages, REVTeX using epsfig.sty. 13 PostScript figures. Final version to appear in Phys. Rev. B. Main changes: Discussion slightly shortened, one figure remove

Linear, Deterministic, and Order-Invariant Initialization Methods for the K-Means Clustering Algorithm

Over the past five decades, k-means has become the clustering algorithm of choice in many application domains primarily due to its simplicity, time/space efficiency, and invariance to the ordering of the data points. Unfortunately, the algorithm's sensitivity to the initial selection of the cluster centers remains to be its most serious drawback. Numerous initialization methods have been proposed to address this drawback. Many of these methods, however, have time complexity superlinear in the number of data points, which makes them impractical for large data sets. On the other hand, linear methods are often random and/or sensitive to the ordering of the data points. These methods are generally unreliable in that the quality of their results is unpredictable. Therefore, it is common practice to perform multiple runs of such methods and take the output of the run that produces the best results. Such a practice, however, greatly increases the computational requirements of the otherwise highly efficient k-means algorithm. In this chapter, we investigate the empirical performance of six linear, deterministic (non-random), and order-invariant k-means initialization methods on a large and diverse collection of data sets from the UCI Machine Learning Repository. The results demonstrate that two relatively unknown hierarchical initialization methods due to Su and Dy outperform the remaining four methods with respect to two objective effectiveness criteria. In addition, a recent method due to Erisoglu et al. performs surprisingly poorly.Comment: 21 pages, 2 figures, 5 tables, Partitional Clustering Algorithms (Springer, 2014). arXiv admin note: substantial text overlap with arXiv:1304.7465, arXiv:1209.196