Theoretical and computation modelling of polymer seal life

Elastomer seals are widely used in the petroleum industry. Seal failure can be very expensive, due to losses in production and high maintenance costs. Another aspect of this problem is the difficulty in predicting the working life, of a specific elastomeric seal in a specific application, at the design stage. The objective of the present work is to develop the theoretical and computational seal life model to assist reliable prediction of seal life. Seal life computer software has been developed to model fluid ingress into elastomeric seals and the resulting long term material property changes caused by volume swell and chemical reaction between elastomer and ingressed fluid. The approach used is to model diffusion using a finite element method. This permits application to a wide range of seal geometries. The mathematical model of diffusion is coupled with chemical reaction equations of second order to model chemical ageing processes in the seal. To model the effects of swell, volume of absorbed fluid is coupled with Young's modulus. Physical, as opposed to chemical, stress relaxation is not incorporated since the short time scale of this enable direct measurements to be made. The software has been tested against experimental data for a number of elastomer / operating condition combinations. Satisfactory agreement is obtained for ethylene propylene diene (EPDM) and nitrile rubber aged in air or high pressure water; nitrile and hydrogenated nitrile rubber (HNBR) aged in high temperature, high pressure hydrocarbon liquid. The software has also been found useful for calculating required soak time in planning rig tests for the study of explosive decompression caused by absorbed gas in elastomers. Pending further development of the software, long term prediction of retained sealing force of O-rings in high temperature, high pressure water is calculated from compression set by a semi-empirical approach. Results are compared with experimental data

The Unforeseen Consequences of Interacting With Non‐Native Speakers

Sociolinguistic research shows that listeners' expectations of speakers influence their interpretation of the speech, yet this is often ignored in cognitive models of language comprehension. Here, we focus on the case of interactions between native and non-native speakers. Previous literature shows that listeners process the language of non-native speakers in less detail, because they expect them to have lower linguistic competence. We show that processing the language of non-native speakers increases lexical competition and access in general, not only of the non-native speaker's speech, and that this leads to poorer memory of one's own speech during the interaction. We further find that the degree to which people adjust their processing to non-native speakers is related to the degree to which they adjust their speech to them. We discuss implications for cognitive models of language processing and sociolinguistic research on attitudes

Anomalous morphology in left hemisphere motor and premotor cortex of children who stutter

Stuttering is a neurodevelopmental disorder that affects the smooth flow of speech production. Stuttering onset occurs during a dynamic period of development when children first start learning to formulate sentences. Although most children grow out of stuttering naturally, ∼1% of all children develop persistent stuttering that can lead to significant psychosocial consequences throughout one’s life. To date, few studies have examined neural bases of stuttering in children who stutter, and even fewer have examined the basis for natural recovery versus persistence of stuttering. Here we report the first study to conduct surface-based analysis of the brain morphometric measures in children who stutter. We used FreeSurfer to extract cortical size and shape measures from structural MRI scans collected from the initial year of a longitudinal study involving 70 children (36 stuttering, 34 controls) in the 3–10-year range. The stuttering group was further divided into two groups: persistent and recovered, based on their later longitudinal visits that allowed determination of their eventual clinical outcome. A region of interest analysis that focused on the left hemisphere speech network and a whole-brain exploratory analysis were conducted to examine group differences and group × age interaction effects. We found that the persistent group could be differentiated from the control and recovered groups by reduced cortical thickness in left motor and lateral premotor cortical regions. The recovered group showed an age-related decrease in local gyrification in the left medial premotor cortex (supplementary motor area and and pre-supplementary motor area). These results provide strong evidence of a primary deficit in the left hemisphere speech network, specifically involving lateral premotor cortex and primary motor cortex, in persistent developmental stuttering. Results further point to a possible compensatory mechanism involving left medial premotor cortex in those who recover from childhood stuttering.This study was supported by Award Numbers R01DC011277 (SC) and R01DC007683 (FG) from the National Institute on Deafness and other Communication Disorders (NIDCD). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIDCD or the National Institutes of Health. (R01DC011277 - National Institute on Deafness and other Communication Disorders (NIDCD); R01DC007683 - National Institute on Deafness and other Communication Disorders (NIDCD))Accepted manuscrip

Hereditary Colorectal Cancer Syndromes in Hong Kong: a Registry's Perspective

Established in 1995, the Hereditary Gastrointestinal Cancer Registry aimed at cancer prevention due to hereditary colorectal cancer syndromes in Hong Kong through early detection, timely treatment, education and ongoing research. This article details the history, structure and work of the Registry. A summary is also provided on the results of various research work conducted by the Registry which facilitates the clinical management of hereditary colorectal cancer syndromes in Hong Kong Chinese families

Interventions for trachoma trichiasis.

BACKGROUND: Trachoma is the leading infectious cause of blindness. The World Health Organization (WHO) recommends eliminating trachomatous blindness through the SAFE strategy: Surgery for trichiasis, Antibiotic treatment, Facial cleanliness and Environmental hygiene. This is an update of a Cochrane review first published in 2003, and previously updated in 2006. OBJECTIVES: To assess the effects of interventions for trachomatous trichiasis for people living in endemic settings. SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2015, Issue 4), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to May 2015), EMBASE (January 1980 to May 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 7 May 2015. We searched the reference lists of included studies to identify further potentially relevant studies. We also contacted authors for details of other relevant studies. SELECTION CRITERIA: We included randomised trials of any intervention intended to treat trachomatous trichiasis. DATA COLLECTION AND ANALYSIS: Three review authors independently selected and assessed the trials, including the risk of bias. We contacted trial authors for missing data when necessary. Our primary outcome was post-operative trichiasis which was defined as any lash touching the globe at three months, one year or two years after surgery. MAIN RESULTS: Thirteen studies met the inclusion criteria with 8586 participants. Most of the studies were conducted in sub-Saharan Africa. The majority of the studies were of a low or unclear risk of bias.Five studies compared different surgical interventions. Most surgical interventions were performed by non-physician technicians. These trials suggest the most effective surgery is full-thickness incision of the tarsal plate and rotation of the terminal tarsal strip. Pooled data from two studies suggested that the bilamellar rotation was more effective than unilamellar rotation (OR 0.29, 95% CI 0.16 to 0.50). Use of a lid clamp reduced lid contour abnormalities (OR 0.65, 95% CI 0.44 to 0.98) and granuloma formation (OR 0.67, 95% CI 0.46 to 0.97). Absorbable sutures gave comparable outcomes to silk sutures (OR 0.90, 95% CI 0.68 to 1.20) and were associated with less frequent granuloma formation (OR 0.63, 95% CI 0.40 to 0.99). Epilation was less effective at preventing eyelashes from touching the globe than surgery for mild trichiasis, but had comparable results for vision and corneal change. Peri-operative azithromycin reduced post-operative trichiasis; however, the estimate of effect was imprecise and compatible with no effect or increased trichiasis (OR 0.85, 95% CI 0.63 to 1.14; 1954 eyes; 3 studies). Community-based surgery when compared to health centres increased uptake with comparable outcomes. Surgery performed by ophthalmologists and integrated eye care workers was comparable. Adverse events were typically infrequent or mild and included rare postoperative infections, eyelid contour abnormalities and conjunctival granulomas. AUTHORS' CONCLUSIONS: No trials were designed to evaluate whether the interventions for trichiasis prevent blindness as an outcome; however, several found modest improvement in vision following intervention. Certain interventions have been shown to be more effective at eliminating trichiasis. Full-thickness incision of the tarsal plate and rotation of the lash-bearing lid margin was found to be the best technique and is preferably delivered in the community. Surgery may be carried out by an ophthalmologist or a trained ophthalmic assistant. Surgery performed with silk or absorbable sutures gave comparable results. Post-operative azithromycin was found to improve outcomes where overall recurrence was low

The role of sexual imprinting in speciation: lessons from deer mice (genus Peromyscus)

Sexual imprinting, the process of learning mate preferences at a young age, could promote speciation by reducing attraction to individuals from divergent populations or species, consequently creating or maintaining reproductive isolation. Yet, despite the documentation of sexual imprinting in many taxa, its connection to speciation has been understudied. I chose to explore the potential link between sexual imprinting and reproductive isolation and in two North American rodents--the white-footed mouse (Peromyscus leucopus) and its sister species, the cotton mouse (Peromyscus gossypinus). These species have overlapping distributions in nature, possibly allowing interbreeding and admixture. In Chapter 1, I used double-digest restriction-associated DNA sequencing to test for hybridization in sympatric natural populations and found that 1.5% of sampled individuals showed evidence of admixture yet the species have maintained genetic distinctness in sympatry. In the lab, the species hybridize when given no choice of mates but mate more readily with conspecifics, suggesting that mating preferences may prevent hybridization in the wild. In Chapter 2, I tested whether mating preferences create significant reproductive isolation. I measured mating preferences in controlled laboratory conditions and found that both species and sexes preferred conspecific to heterospecific mates in 85% of trials. I then raised offspring with foster parents of the opposite species and found that P. leucopus has a genetically-determined preference while P. gossypinus learns its preference. In Chapter 3, I tested whether sexual imprinting on parental diet could generate assortative mating within a species. I tested this hypothesis by feeding P. gossypinus parents either orange- or garlic-flavored water, thereby exposing their offspring to these flavors through their parents until weaning. I tested the preferences of these offspring as adults and found that P. gossypinus, especially females, had strong assortative mating preferences. This implies that at least females learn parental dietary information and that assortative mating could evolve within a single generation. Together, my results confirm that sexual imprinting on parental traits--possibly mediated through dietary differences--can create assortative mating capable of generating sexual isolation and reducing gene flow between species. My research supports the importance of mating preferences and learning in speciation

Dura Mater

If it weren’t for the way my mother split her apples (seed starred, then flesh dug out to perfect halves)I would never have known how to throw myself at the knif