A multiple scales approach to crack front waves

Perturbation of a propagating crack with a straight edge is solved using the method of matched asymptotic expansions (MAE). This provides a simplified analysis in which the inner and outer solutions are governed by distinct mechanics. The inner solution contains the explicit perturbation and is governed by a quasi-static equation. The outer solution determines the radiation of energy away from the tip, and requires solving dynamic equations in the unperturbed configuration. The outer and inner expansions are matched via the small parameter L/l defined by the disparate length scales: the crack perturbation length L and the outer length scale l associated with the loading. The method is first illustrated for a scalar crack model and then applied to the elastodynamic mode I problem. The dispersion relation for crack front waves is found by requiring that the energy release rate is unaltered under perturbation. The wave speed is calculated as a function of the nondimensional parameter kl where k is the crack front wavenumber, and dispersive properties of the crack front wave speed are described for the first time. The example problems considered here demonstrate that the potential of using MAE for moving boundary value problems with multiple scales.Comment: 25 pages, 5 figure

Cognitive interviewing methodology in the development of a pediatric item bank: a patient reported outcomes measurement information system (PROMIS) study

<p>Abstract</p> <p>Background</p> <p>The evaluation of patient-reported outcomes (PROs) in health care has seen greater use in recent years, and methods to improve the reliability and validity of PRO instruments are advancing. This paper discusses the cognitive interviewing procedures employed by the Patient Reported Outcomes Measurement Information System (PROMIS) pediatrics group for the purpose of developing a dynamic, electronic item bank for field testing with children and adolescents using novel computer technology. The primary objective of this study was to conduct cognitive interviews with children and adolescents to gain feedback on items measuring physical functioning, emotional health, social health, fatigue, pain, and asthma-specific symptoms.</p> <p>Methods</p> <p>A total of 88 cognitive interviews were conducted with 77 children and adolescents across two sites on 318 items. From this initial item bank, 25 items were deleted and 35 were revised and underwent a second round of cognitive interviews. A total of 293 items were retained for field testing.</p> <p>Results</p> <p>Children as young as 8 years of age were able to comprehend the majority of items, response options, directions, recall period, and identify problems with language that was difficult for them to understand. Cognitive interviews indicated issues with item comprehension on several items which led to alternative wording for these items.</p> <p>Conclusion</p> <p>Children ages 8–17 years were able to comprehend most item stems and response options in the present study. Field testing with the resulting items and response options is presently being conducted as part of the PROMIS Pediatric Item Bank development process.</p

Lung Cancer in Pulmonary Fibrosis: Tales of Epithelial Cell Plasticity

Lung epithelial cells exhibit a high degree of plasticity. Alterations to lung epithelial cell function are critically involved in several chronic lung diseases such as pulmonary fibrosis. Pulmonary fibrosis is characterized by repetitive injury and subsequent impaired repair of epithelial cells, which leads to aberrant growth factor activation and fibroblast accumulation. Increased proliferation and hyper- and metaplasia of epithelial cells upon injury have also been observed in pulmonary fibrosis; this epithelial cell activation might represent the basis for lung cancer development. Indeed, several studies have provided histopathological evidence of an increased incidence of lung cancer in pulmonary fibrosis. The mechanisms involved in the development of cancer in pulmonary fibrosis, however, remain poorly understood. This review highlights recently uncovered molecular mechanisms shared between lung cancer and fibrosis, which extend the current evidence of a common trait of cancer and fibrosis, as provided by histopathological observations. Copyright (C) 2011 S. Karger AG, Base

Is metal theft committed by organized crime groups, and why does it matter?

Using the example of metal theft in the United Kingdom, this study used mixed methods to evaluate the accuracy of police estimates of the involvement of organised crime groups (OCGs) in crime. Police estimate that 20-30% of metal theft is committed by OCGs, but this study found that only 0.5% of metal thieves had previous convictions for offences related to OCGs, that only 1.3% were linked to OCGs by intelligence information, that metal thieves typically offended close to their homes and that almost no metal thefts involved sophisticated offence methods. It appears that police may over-estimate the involvement of OCGs in some types of crime. The reasons for and consequences of this over-estimation are discussed

Relationship between early development of spelling and reading

The research reported in this thesis examined the relationship between beginning spelling and reading. More specifically, it focussed on the relationship between the development of early reading and spelling in a context where the approach to early reading instruction includes systematic phonological awareness and decoding instruction. A critical assumption made by proponents of developmental early literacy models is that transfer of skills and knowledge from reading to spelling will occur spontaneously and without formal instruction (Frith, 1980). By contrast instruction-centred approaches make the assumption that there are critical pre-requisite skills that can and should be taught explicitly (Carnine, Silbert & Kameenui, 1997). The difference between these approaches is highlighted in the treatment of invented spelling, a popular activity in Western Australian junior primary classes. A series of studies was undertaken to examine the effect on invented and standard spelling performance of teaching Year 1 children phonological awareness and the strategy of sounding out words. Data were gathered from a range of settings using different research tools. The relationship between phonological awareness and beginning reading and spelling performance was explored initially through a single case study. A post-hoc study was then undertaken with a cohort of students who had received systematic decoding instruction to examine whether proficiency in the decoding of nonwords was related to spelling performance. This permitted an analysis of common sub-skills of decoding and encoding. In the main study the effect on different aspects of reading and spelling performance of using Let\u27s Decode, an approach that includes explicit phonological awareness and systematic decoding instruction, was investigated. In addition, an analysis was made of whether students who received explicit instruction in skills known to contribute to beginning reading and spelling produced superior invented spelling samples. A qualitative analysis was made of the. pre and post invented spelling tests of two pairs of students from the control and intervention groups matched on invented spelling and phonological awareness skills at the beginning of the year, and re tested at the end of Year 1. The final research question involved a single-subject research design to examine the effect of explicit instruction in isolating phonemes in words and prompts to \u27listen for sounds\u27 prior to, and during, the process of spelling words. The single case study revealed a child who was regarded as a competent speller and reader but who could only read words in a familiar context and who had developed a strategy for spelling words based on copying an adult model. This was interpreted as evidence supporting the need for phonological awareness instruction as a pre-requisite for spelling. The post-hoc analysis of a class of students who had received systematic decoding instruction showed that no student classified as a \u27good decoder\u27 could also be classified as a \u27poor speller\u27. This result was considered evidence of a strong link between the phonological knowledge that is required to decode and the role of alphabetic knowledge in spelling. The main study revealed phonological awareness and systematic decoding instruction was associated with superior invented and conventional spelling and reading performance on all reading and spelling measures. Of particular importance was the finding that students who commenced the study with very weak phonological awareness and who subsequently received systematic phonological and decoding instruction showed greater gains in invented spelling than matched students in the control condition. The single subject design showed the effectiveness of phonological awareness individualised instruction on invented spelling for weak students from both intervention and control conditions. It was concluded that the ability to invent spelling is improved when students receive explicit instruction in phonological awareness and systematic decoding but that some students, namely those with persistent weakness in phonological awareness, also require explicit prompts to apply their alphabetic knowledge to spelling words. The implications for instruction of these findings are discussed

Gac two-component system in Pseudomonas syringae pv. tabaci is required for virulence but not for hypersensitive reaction

Pseudomonas syringae pv. tabaci 6605 causes wildfire disease on host tobacco plants. To investigate the regulatory mechanism of the expression of virulence, Gac two-Component system-defective mutants, Delta gacA and Delta gacS, and a double mutant, Delta gacA Delta gacS, were generated. These mutants produced smaller amounts of N-acyl homoserine lactones required for quorum sensing, had lost swarming motility, and had reduced expression of virulence-related hrp genes and the algT gene required for exopolysaccharide production. The ability of the mutants to cause disease symptoms in their host tobacco plant was remarkably reduced, while they retained the ability to induce hypersensitive reaction (HR) in the nonhost plants. These results indicated that the Gac two-component system of P. syringae pv. tabaci 6605 is indispensable for virulence on the host plant, but not for HR induction in the nonhost plants.</p

Cognitive interviewing methodology in the development of a pediatric item bank: a patient reported outcomes measurement information system (PROMIS) study

<p>Abstract</p> <p>Background</p> <p>The evaluation of patient-reported outcomes (PROs) in health care has seen greater use in recent years, and methods to improve the reliability and validity of PRO instruments are advancing. This paper discusses the cognitive interviewing procedures employed by the Patient Reported Outcomes Measurement Information System (PROMIS) pediatrics group for the purpose of developing a dynamic, electronic item bank for field testing with children and adolescents using novel computer technology. The primary objective of this study was to conduct cognitive interviews with children and adolescents to gain feedback on items measuring physical functioning, emotional health, social health, fatigue, pain, and asthma-specific symptoms.</p> <p>Methods</p> <p>A total of 88 cognitive interviews were conducted with 77 children and adolescents across two sites on 318 items. From this initial item bank, 25 items were deleted and 35 were revised and underwent a second round of cognitive interviews. A total of 293 items were retained for field testing.</p> <p>Results</p> <p>Children as young as 8 years of age were able to comprehend the majority of items, response options, directions, recall period, and identify problems with language that was difficult for them to understand. Cognitive interviews indicated issues with item comprehension on several items which led to alternative wording for these items.</p> <p>Conclusion</p> <p>Children ages 8–17 years were able to comprehend most item stems and response options in the present study. Field testing with the resulting items and response options is presently being conducted as part of the PROMIS Pediatric Item Bank development process.</p

Analytical Pluralism in Qualitative Research: A Meta-Study

Recent interest in analytical pluralism – the application of more than one qualitative analytical method to a single data set – has demonstrated its potential to produce multiple, complex and varied understandings of phenomena. However tensions remain regarding the commensurability of findings produced from diverse theoretical frameworks, the practical application of multiple methods of analysis and the capacity of pluralism to contribute to knowledge in psychology. This study addresses these issues, through a critical interpretation of existing qualitative studies that utilised analytical pluralism. Using a meta-study design, we examined the use of theory, application of methods and production of findings in studies that had adopted qualitative analytical pluralism. Following comprehensive database searches, 10 articles were included in the analysis. Epistemological and ontological considerations, the influence of decisions made in the practical application of pluralism and approaches to interpreting findings produced from multiple analyses are discussed, and implications for future research are considered

The role of intradiscal steroids in the treatment of discogenic low back pain

LBP is one of the most common reasons for visiting a doctor and is the most common cause of disability under age 45.Amongst a variety of etiologies, internal disc disruption (IDD) has been postulated as an important cause of low back pain. Treating discogenic low back pain continues to be a challenge to physicians. Inflammation, either from direct chemical irritation or secondary to an autoimmune response to the nucleus pulposus has been implicated as the primary pain source. Both steroids and non-steroidal anti-inflammatory drugs have partial effectiveness in treating pain associated with inflammation. Therefore, the rationale for using intradiscal steroids is to suppress the inflammation within the disc, thereby alleviating the patient’s symptoms. The goal of this article is to review the literature regarding the efficacy of intradiscal steroids to treat low back pain of discogenic origin