A mathematical model for estimating the extent of solute- and water-flux heterogeneity in multiple sample percolation experiments

Multiple sampling is widely used in vadose zone percolation experiments to investigate the extent in which soil structure heterogeneities influence the spatial and temporal distributions of water and solutes. In this note, a simple, robust, mathematical model, based on the beta-statistical distribution, is proposed as a method of quantifying the magnitude of heterogeneity in such experiments. The model relies on fitting two parameters, alpha and zeta to the cumulative elution curves generated in multiple-sample percolation experiments. The model does not require knowledge of the soil structure. A homogeneous or uniform distribution of a solute and/or soil-water is indicated by alpha = zeta = 1, Using these parameters, a heterogeneity index (HI) is defined as root 3 times the ratio of the standard deviation and mean. Uniform or homogeneous flow of water or solutes is indicated by HI = 1 and heterogeneity is indicated by HI > 1. A large value for this index may indicate preferential flow. The heterogeneity index relies only on knowledge of the elution curves generated from multiple sample percolation experiments and is, therefore, easily calculated. The index may also be used to describe and compare the differences in solute and soil-water percolation from different experiments. The use of this index is discussed for several different leaching experiments. (C) 1999 Elsevier Science B.V. All rights reserved.

Parent training skills and methadone maintenance: clinical opportunities and challenges

Children raised in substance abusing families show high rates of behavioural and emotional problems, in particular oppositional, defiant and non-compliant behaviours. While a range of social and individual factors correlate with poor parenting, it is often the quality of the parent-child relationship that mediates the effects of most other risk factors on child development. By addressing this relationship using behavioural family interventions, child behaviour problems have been reduced in multiple problem families. However, there has been little attempt to systematically evaluate such programs in substance abusing families. It is argued that methadone replacement programs provide a window of opportunity to deliver well-validated parent training programs that enhance the quality of parent-child relations. However, it is likely that such programs would need to be medium to long term and address issues beyond parent child relationships. How such interventions may be delivered and evaluated is discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

Development and standardization of the Self-regulation Skills Interview (SRSI): A new clinical assessment tool for acquired brain injury

The Self-regulation Skills Interview (SRSI) is a clinical tool designed to measure a range of metacognitive skills essential for rehabilitation planning, monitoring an individual's progress, and evaluating the outcome of treatment interventions. The results of the present study indicated that the SRSI has sound interrater reliability and test-retest reliability. A principle components analysis revealed three SRSI factors: Awareness, Readiness to Change, and Strategy Behavior. A comparison between a group of 61 participants with acquired brain injury (ABI) and a group of 43 non-brain-injured participants indicated that the participants with ABI had significantly lower levels of Awareness and Strategy Behavior, but that level of Readiness to Change was not significantly different between the two groups. The significant relationship observed between the SRSI factors and measures of neuropsychological functioning confirmed the concurrent validity of the scale and supports the value of the SRSI for post-acute assessment.

Spelling in adults: The role of reading skills and experience

One hundred university students completed tests of spelling production, vocabulary, reading comprehension, reading experience, and reading accuracy (ability to distinguish a previously read word from a similar distractor). Reading experience, as measured by an adaptation of the Author Recognition Test, and reading accuracy contributed to the prediction of spelling beyond the joint contribution of reading comprehension and vocabulary. The results are more consistent with a uni-process model of spelling based on the quality of word-specific orthographic learning, rather than with a dual-process account relying on both word-specific knowledge and rules.

Modelling socially optimal land allocations for sugar cane growing in North Queensland: a linked mathematical programming and choice modelling study

A modelling framework is developed to determine the joint economic and environmental net benefits of alternative land allocation strategies. Estimates of community preferences for preservation of natural land, derived from a choice modelling study, are used as input to a model of agricultural production in an optimisation framework. The trade-offs between agricultural production and environmental protection are analysed using the sugar industry of the Herbert River district of north Queensland as an example. Spatially-differentiated resource attributes and the opportunity costs of natural land determine the optimal tradeoffs between production and conservation for a range of sugar prices.

Mathematical models in percutaneous absorption

A number of mathematical models have been used to describe percutaneous absorption kinetics. In general, most of these models have used either diffusion-based or compartmental equations. The object of any mathematical model is to a) be able to represent the processes associated with absorption accurately, b) be able to describe/summarize experimental data with parametric equations or moments, and c) predict kinetics under varying conditions. However, in describing the processes involved, some developed models often suffer from being of too complex a form to be practically useful. In this chapter, we attempt to approach the issue of mathematical modeling in percutaneous absorption from four perspectives. These are to a) describe simple practical models, b) provide an overview of the more complex models, c) summarize some of the more important/useful models used to date, and d) examine sonic practical applications of the models. The range of processes involved in percutaneous absorption and considered in developing the mathematical models in this chapter is shown in Fig. 1. We initially address in vitro skin diffusion models and consider a) constant donor concentration and receptor conditions, b) the corresponding flux, donor, skin, and receptor amount-time profiles for solutions, and c) amount- and flux-time profiles when the donor phase is removed. More complex issues, such as finite-volume donor phase, finite-volume receptor phase, the presence of an efflux. rate constant at the membrane-receptor interphase, and two-layer diffusion, are then considered. We then look at specific models and issues concerned with a) release from topical products, b) use of compartmental models as alternatives to diffusion models, c) concentration-dependent absorption, d) modeling of skin metabolism, e) role of solute-skin-vehicle interactions, f) effects of vehicle loss, a) shunt transport, and h) in vivo diffusion, compartmental, physiological, and deconvolution models. We conclude by examining topics such as a) deep tissue penetration, b) pharmacodynamics, c) iontophoresis, d) sonophoresis, and e) pitfalls in modeling.

Cancer knowledge and skills of interns in Australia and New Zealand in 2001: comparison with 1990, and between course types

Objective: To compare the cancer knowledge and skills of interns in 2001 who graduated from graduate medical program (GMP) courses with those from non-GMP courses, and to compare the cancer knowledge and skills of interns in 2001 with those who completed a similar survey in 1990. Design: Questionnaire survey of recently graduated interns in a random sample of Australian and New Zealand hospitals. The questionnaire was designed to allow direct comparison with the 1990 survey, and was guided by the Australian Cancer Society's Ideal Oncology Curriculum for Medical Schools. Results: 443 interns completed the survey (response rate, 62%; 42 were excluded, leaving 401 surveys for analysis: 118 from GMP courses and 283 from non-GMP courses). Interns from GMP courses felt more competent than those from non-GMP courses at discussing death (P= 0.02), breaking bad news (P= 0.04) and advising on smoking cessation (P= 0.02), but less competent at preparing a patient for a hazardous procedure (P= 0.02). Mote GMP interns would refer a breast cancer patient to a multidisciplinary clinic (83% versus 70%; P= 0.03). Knowledge about cancer risks and prognosis was significantly less in GMP interns, but GMP interns rated their clinical skills, such as taking a Pap smear, higher than non-GMP interns. The GMP and non-GMP groups did not differ in their exposure to cancer patients, but compared with 1990 interns recent graduates had less exposure to patients with cancer. Conclusions: GMP curricula appear to have successfully introduced new course material and new methods of teaching, but have not always succeeded in producing doctors with better knowledge about cancer. Recent graduates have less exposure to cancer patients than those who trained 10 years ago.

Characterisation of the three-dimensional structure of earthworm burrow systems using image analysis and mathematical morphology

The aim of this work was to exemplify the specific contribution of both two- and three-dimensional (31)) X-ray computed tomography to characterise earthworm burrow systems. To achieve this purpose we used 3D mathematical morphology operators to characterise burrow systems resulting from the activity of an anecic (Aporrectodea noctunia), and an endogeic species (Allolobophora chlorotica), when both species were introduced either separately or together into artificial soil cores. Images of these soil cores were obtained using a medical X-ray tomography scanner. Three-dimensional reconstructions of burrow systems were obtained using a specifically developed segmentation algorithm. To study the differences between burrow systems, a set of classical tools of mathematical morphology (granulometries) were used. So-called granulometries based on different structuring elements clearly separated the different burrow systems. They enabled us to show that burrows made by the anecic species were fatter, longer, more vertical, more continuous but less sinuous than burrows of the endogeic species. The granulometry transform of the soil matrix showed that burrows made by A. nocturna were more evenly distributed than those of A. chlorotica. Although a good discrimination was possible when only one species was introduced into the soil cores, it was not possible to separate burrows of the two species from each other in cases where species were introduced into the same soil core. This limitation, partly due to the insufficient spatial resolution of the medical scanner, precluded the use of the morphological operators to study putative interactions between the two species.

Mathematical constraints on a theory of human memory - Response

Colonius suggests that, in using standard set theory as the language in which to express our computational-level theory of human memory, we would need to violate the axiom of foundation in order to express meaningful memory bindings in which a context is identical to an item in the list. We circumvent Colonius's objection by allowing that a list item may serve as a label for a context without being identical to that context. This debate serves to highlight the value of specifying memory operations in set theoretic notation, as it would have been difficult if not impossible to formulate such an objection at the algorithmic level.

Phonological sensitivity as a proximal contributor to phonological recoding skills in children's reading

Because it permits self-teaching, phonological recoding (the efficient translation of letters or letter groups into sound) is arguably the key skill acquired in learning to read an alphabetic writing system. Deficits in this skill are the most common source of children's reading difficulties. In addition, poor readers tend to perform at a lower level than good readers on a wide variety of phonological processing tasks. These findings have been widely interpreted as implying a latent phonological processing ability as a distal cause of variation in reading skill. Clearly, such an interpretation does not imply that all phonological processing skills contribute directly to the phonological recoding process. This paper outlines a series of studies conducted at the University of Queensland. This work consistently suggests that children's phonological sensitivity contributes more directly than other phonological processing abilities to the development of phonological recoding skills.

Enhancing the phonological processing skills of children with specific reading disability

The present study evaluated the benefits of phonological processing skills training for children with persistent reading difficulties. Children aged between 9-14 years, identified as having a specific reading disability, participated in the study. In a series of three experiments, pedagogical issues related to length of training time, model of intervention and severity of readers' phonological processing skills deficit prior to intervention, were explored. The results indicated that improvement in poor readers' phonological processing skills led to a dramatic improvement in their reading accuracy and reading comprehension performance. Increasing the length of training time significantly improved transfer effects to the reading process. Children with particularly severe phonological processing skill deficits benefited from art extended training period, and both individual and group intervention models for phonological processing training proved successful. Implications for speech and language therapists are discussed.

A mathematical model for Escherichia coli debris size reduction during high pressure homogenisation based on grinding theory

Experimental data for E. coli debris size reduction during high-pressure homogenisation at 55 MPa are presented. A mathematical model based on grinding theory is developed to describe the data. The model is based on first-order breakage and compensation conditions. It does not require any assumption of a specified distribution for debris size and can be used given information on the initial size distribution of whole cells and the disruption efficiency during homogenisation. The number of homogeniser passes is incorporated into the model and used to describe the size reduction of non-induced stationary and induced E. coil cells during homogenisation. Regressing the results to the model equations gave an excellent fit to experimental data ( > 98.7% of variance explained for both fermentations), confirming the model's potential for predicting size reduction during high-pressure homogenisation. This study provides a means to optimise both homogenisation and disc-stack centrifugation conditions for recombinant product recovery. (C) 1997 Elsevier Science Ltd.

Validation of ASHA FACS-Functional Assessment of Communication Skills for Alzheimer Disease Population

This study vas aimed to validate the American Speech-Language-Hearing Association Functional Assessment Of Communication Skills (ASHA FACS) for a Brazilian population. The scale was translated and adapted into Portuguese. Thirty-two patients with mild Alzheimer disease (AD). 25 patients with moderate AD. and 51 elderly without dementia were examined with Mini Mental State Examination, Geriatric Depression Scale. and Alzheimer Disease Assessment Scale-Cognitive subscale (ADAS-cog). The ASHA FACS was answered by their relative/caregiver. The scale`s internal consistency. its inter-examiner and intra-examiner`s reproducibility. and scale`s criterion validity were researched by correlation with ADAS-cog,. The sensitivity and specificity Were also researched. Statistical analyses indicated that the ASHA FACS has excellent internal consistency (Cronbach alpha = 0.955), test-retest reliability (interclass correlation coefficient = 0.995; P < 0.001). and inter-examiners (interclass correlation coefficient = 0.998: P < 0.001). It showed excellent criterion validity when correlated with ADAS-cog,. The ASHA FACS scale showed good sensitivity (75.0%) and specificity (82.4%) values once it is an ecologic and broad evaluation. The ASHA FACS Portuguese version is a valid and reliable instrument to verify communication alterations in AD patients and fills an important gap of efficiency indicators for speech language therapy in our country.

A comparison of the expressive communication skills of triplet, twin and singleton children

Few studies have focused on the language acquisition of higher multiple birth sets. In this study, the communication skills of 51 triplet children are described. The measures used were: mean length of utterance; type-token ratio; conversational nets; phoneme repertoire; and number of different types of phonological processes used. The data gained were used to compare the communication skills of triplets with those of twins, singletons and normative data available in the literature. Siblings within triplet sets were also compared using language samples obtained from adult-child interactions and when the three children were playing together. The results indicated that the triplets' early communication skills were different from those of both singletons and twins. The triplets' difficulties included delayed syntactic development, limited use of different language functions and delayed phonological development. In contrast, twins' communication profile is characterised by disordered phonological development.