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Jason Noble

Publications and source records attributed to Jason Noble.

13 recordsLinked to original sources
PubMed2006

Homeostatic plasticity improves signal propagation in continuous-time recurrent neural networks.

Continuous-time recurrent neural networks (CTRNNs) are potentially an excellent substrate for the generation of adaptive behaviour in artificial autonomous agents. However, node saturation effects in these networks can leave them insensitive to input and stop signals from propagating. Node saturation is related to the problems of hyper-excitation and quiescence in biological nervous systems, which are thought to be avoided through the existence of homeostatic plastic mechanisms. Analogous mechanisms are here implemented in a variety of CTRNN architectures and are shown to increase node sensitivity and improve signal propagation, with implications for robotics. These results lend support to the view that homeostatic plasticity may prevent quiescence and hyper-excitation in biological nervous systems.

Homeostasis↗
PubMed2006

Quality of life and return to work following electrical burns.

To investigate the psychosocial outcomes following electrical burns, a cross-sectional survey of electrical burn patients was done using three outcome tools: the Burn Specific Health Scale brief version (BSHS-B), the Coping with Burns Questionnaire (CBQ), and the Pain Patient Profile (P3). Questionnaires were mailed to electrical burn patients discharged from an adult regional burn centre, and also distributed to attendants of an electrical utility conference in Toronto. Twenty-six of 88 patients who were discharged from the regional burn centre during the study period with updated residential information were contacted and 14 (54%) completed the questionnaires. Twenty questionnaires were also distributed at the conference and 8 (40%) were completed; leaving a total of 22 (48%) patients for the study. The average patient age was 44.0+/-11.7 years; 21 (96%) were men, and the average time from injury to survey completion was 5.3+/-4.9 years. Five (23%) of the 22 patients returned to the same work duties, 10 (45%) changed duties, and 7 (32%) did not return to work. BSHS-B scores were low for all patients. Participants with high voltage burns (>1000 V) had worse sexuality scores (p<0.05), while those with larger burns (>10% TBSA) had worse physical scores (p<0.05). Patients surveyed >5 years from injury showed improvement in physical scores. CBQ scores indicated that optimism was the most commonly used coping strategy. P3 showed significant levels of emotional distress in all patients, with anxiety being more common in high voltage injuries (p<0.05). The data suggests that electrical burn patients may have a limited ability to return to work and an overall poor quality of life. Emotional distress is the dominant feature influencing long-term outcome in these patients. Further studies are warranted to validate these findings.

Activities of Daily Living↗
PubMed2006

Utility of the National Eye Institute VFQ-25 questionnaire in a heterogeneous group of multiple sclerosis patients.

PURPOSE: To investigate the utility of the 25-Item National Eye Institute Visual Function Questionnaire (VFQ-25) in assessing visual function in a heterogeneous group of multiple sclerosis (MS) patients and to identify correlations of VFQ-25 scores with clinically relevant objective visual parameters. DESIGN: Comparative cohort study. METHODS: The VFQ-25 was distributed to 34 patients with clinically definite MS. Patients underwent a comprehensive ophthalmic examination, including Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (V(A)), Pelli-Robson contrast sensitivity (CS), Humphrey visual field 30 to 2 (HVF), and Farnsworth-Munsell 100-Hue color vision (100-Hue). Expanded Disability Status Scores (EDSS) were recorded for each patient. Comparative analyses using chi2 tests and t tests were performed. Spearman rank correlation coefficients were computed to identify relationships between VFQ-25 scores and the aforementioned visual parameters. RESULTS: In comparison with a published reference group without ocular disease, MS patients had considerably worse VFQ-25 composite scores (P < .01), being similar to published cohorts of glaucoma and cataract patients. VFQ-25 composite scores were found to be modestly and significantly correlated with several clinical parameters, including: V(A) (r = -0.63, P < .001), CS (r = 0.60, P < .001), HVF (r = 0.53, P = .003), and 100-Hue (r = -0.48, P = .01). EDSS scores, the use of disease modifying agents, and having a history of previous optic neuritis did not correlate significantly with VFQ-25 composite scores. CONCLUSIONS: The VFQ-25 questionnaire is a sensitive and useful tool in assessing visual function in MS patients. Such patients have quality of life indices similar to glaucoma and cataract patients, underscoring the significance of visual symptoms in MS.

Adult↗
PubMed2006

Factors influencing career choice in ophthalmology.

BACKGROUND: To investigate the factors influencing choice of ophthalmology as a career in medicine. METHODS: Data were extracted from the 2004 National Physician Survey, a questionnaire distributed to all physicians across Canada. Data were categorized by medical discipline, and chi2 comparative analyses were done. RESULTS: Intellectual stimulation emerged as the most frequently cited factor influencing career choice for ophthalmologists and nonophthalmologists alike (81% and 79%, respectively). Compared with other physicians, ophthalmologists were significantly more likely to cite flexibility (58% vs. 42%, respectively), mentorship (42% vs. 31%, respectively), and earning potential (38% vs. 26%, respectively) as important factors (p<0.001). INTERPRETATION: Intellectual stimulation is the principal reason physicians pursue a career in ophthalmology. Ophthalmologists cite flexibility, mentorship, and earning potential as important factors more frequently than do physicians of other disciplines.

Attitude of Health Personnel↗
PubMed2006

Does sex affect the success rate of Canadian ophthalmology residency applicants?

BACKGROUND: Despite equalization of the ratio of men and women among matriculating medical students, it is possible that different rates of success for applicants at the level of resident selection in the annual residency match may occur on the basis of sex. As part of a larger project, we examined this issue across the medical specialties. In the current article, the effect of sex on resident selection within the specialty of ophthalmology is explored. METHODS: Data were obtained from the Canadian Medical Association, Canadian Institute for Health Information, Royal College of Physicians and Surgeons of Canada, Canadian Ophthalmological Society, and Canadian Residency Matching Service regarding sex- and age-specific demographics, as well as success rates for male and female applicants ranking an ophthalmology residency program as their top choice. The proportion of men who ranked ophthalmology as their top choice but did not match to any ophthalmology program was compared to the corresponding proportion of women. RESULTS: The female: male ratio of practicing ophthalmologists has slowly increased over the past decade and is highest (0.41:1) within the under-45 age group. By grouping data from 1993 to 2004, we found that men who ranked an ophthalmology program as their first choice had odds of not being accepted to an ophthalmology program that were 1.1 times (95% confidence interval 0.8-2.0; p=0.34) the corresponding odds for women. INTERPRETATION: Our data suggest that discrimination on the basis of sex does not occur at the level of residency selection. The lower level of female recruitment may be due to decreased interest in this specialty among women. Nonetheless, the proportion of female ophthalmologists within the Canadian workforce continues to increase.

Canada↗
PubMed2006

Future practice profiles of Canadian medical trainees.

PURPOSE: To investigate the future practice profiles of Canadian medical trainees. METHODS: Data were extracted from the 2004 National Physician Survey, a questionnaire distributed to medical students, residents and physicians across Canada. Data were categorized by level of training and chi-square comparative analyses were done. RESULTS: The majority of trainees (about 64%) expressed plans to practice in the location in which they were training, with approximately 12% planning on practicing in another country. Family medicine (FM) residents were more likely to express wishes to practice in their location of training when compared to medical students and specialty residents. CONCLUSIONS: The location of training directly affects the future practice plans of Canadian medical trainees. Retaining specialist physicians may represent a challenge in the future.

Career Choice↗
PubMed2005

Extrascleral extension in association with ciliochoroidal melanoma: ultrasound biomicroscopy with histopathological correlation.

CASE REPORT: We present the case of a 71-year-old man with a melanoma arising from the ciliary body and extending into the choroid. Ultrasound biomicroscopy (UBM) revealed connection via an emissary canal to a subconjunctival nodule. Although evaluation for metastasis was negative at the time of diagnosis, multiple hepatic metastatic deposits were found 2 years post-enucleation. COMMENTS: It is crucial to identify the presence of scleral invasion and extrascleral extension for proper management planning in patients with choroidal melanomas. This case demonstrates that UBM is an accurate and useful tool for characterizing the morphologic pattern of scleral invasion of intraocular tumours.

Aged↗
PubMed2005

Management of type 2 diabetes mellitus. Role of thiazolidinediones.

OBJECTIVE: To review evidence supporting use of thiazolidinediones (TZDs) in management of type 2 diabetes mellitus (DM2). QUALITY OF EVIDENCE: A MEDLINE search found several randomized controlled trials (level I evidence). No systematic reviews of these trials were found in the Cochrane Library. MAIN MESSAGE: Thiazolidinediones lower hemoglobin AIc levels by as much as 1.0% to 1.5%. Effects can be seen in as little as 4 weeks, but full lowering takes 6 to 12 weeks. When used in combination with other diabetic agents, such as sulfonylureas and biguanides, TZDs' hypoglycemic effects appear to be complementary. Thiazolidinediones directly improve insulin sensitivity and recovery of pancreatic beta cell function. Nevertheless, there is no evidence indicating that TZDs are superior to other antidiabetic agents currently available or that TZDs reduce the long-term complications of DM2. CONCLUSION: Ongoing trials will further define the role of TZDs in management of diabetic patients. In current practice, cost is often a factor in the decision to prescribe TZDs.

Diabetes Mellitus, Type 2↗
PubMed2004

Warning signals and predator-prey coevolution.

Theories of the evolution of warning signals are typically expressed using analytic and computational models, most of which attribute aspects of predator psychology as the key factors facilitating the evolution of warning signals. Sherratt provides a novel and promising perspective with a model that considers the coevolution of predator and prey populations, showing how predators may develop a bias towards attacking cryptic prey in preference to conspicuous prey. Here, we replicate the model as an individual-based simulation and find, in accordance with Sherratt, that predators evolve a bias towards attacking cryptic prey. We then use a Monte Carlo simulation to calculate the relative survivorships of cryptic and conspicuous prey and stress that, as it stands, the model does not predict the evolution or stability of warning signals. We extend the model by giving predators continuous attack strategies and by allowing the evolution of prey conspicuousness: results are robust to the first modification but, in all cases, cryptic prey always enjoy a higher survivorship than conspicuous prey. When conspicuousness is allowed to evolve, prey quickly evolve towards crypsis, even when runaway coevolution is enabled. Sherratt's approach is promising, but other aspects of predator psychology, besides their innate response, remain vital to our understanding of warning signals.

Animals↗
PubMed2004

Batesian mimics influence mimicry ring evolution.

Mathematical models of mimicry typically involve artificial prey species with fixed colorations or appearances; this enables a comparison of predation rates to demonstrate the level of protection a mimic might be afforded. Fruitful theoretical results have been produced using this method, but it is also useful to examine the possible evolutionary consequences of mimicry. To that end, we present individual-based evolutionary simulation models where prey colorations are free to evolve. We use the models to examine the effect of Batesian mimics on Müllerian mimics and mimicry rings. Results show that Batesian mimics can potentially incite Müllerian mimicry relationships and encourage mimicry ring convergence.

Animals↗
PubMed2003

Proteomic profiling of urinary proteins in renal cancer by surface enhanced laser desorption ionization and neural-network analysis: identification of key issues affecting potential clinical utility.

Recent advances in proteomic profiling technologies, such as surface enhanced laser desorption ionization mass spectrometry, have allowed preliminary profiling and identification of tumor markers in biological fluids in several cancer types and establishment of clinically useful diagnostic computational models. There are currently no routinely used circulating tumor markers for renal cancer, which is often detected incidentally and is frequently advanced at the time of presentation with over half of patients having local or distant tumor spread. We have investigated the clinical utility of surface enhanced laser desorption ionization profiling of urine samples in conjunction with neural-network analysis to either detect renal cancer or to identify proteins of potential use as markers, using samples from a total of 218 individuals, and examined critical technical factors affecting the potential utility of this approach. Samples from patients before undergoing nephrectomy for clear cell renal cell carcinoma (RCC; n = 48), normal volunteers (n = 38), and outpatients attending with benign diseases of the urogenital tract (n = 20) were used to successfully train neural-network models based on either presence/absence of peaks or peak intensity values, resulting in sensitivity and specificity values of 98.3-100%. Using an initial "blind" group of samples from 12 patients with RCC, 11 healthy controls, and 9 patients with benign diseases to test the models, sensitivities and specificities of 81.8-83.3% were achieved. The robustness of the approach was subsequently evaluated with a group of 80 samples analyzed "blind" 10 months later, (36 patients with RCC, 31 healthy volunteers, and 13 patients with benign urological conditions). However, sensitivities and specificities declined markedly, ranging from 41.0% to 76.6%. Possible contributing factors including sample stability, changing laser performance, and chip variability were examined, which may be important for the long-term robustness of such approaches, and this study highlights the need for rigorous evaluation of such factors in future studies.

Adult↗
PubMed2002

The view from elsewhere: perspectives on ALife modeling.

Many artificial life researchers stress the interdisciplinary character of the field. Against such a backdrop, this report reviews and discusses artificial life, as it is depicted in, and as it interfaces with, adjacent disciplines (in particular, philosophy, biology, and linguistics), and in the light of a specific historical example of interdisciplinary research (namely cybernetics) with which artificial life shares many features. This report grew out of a workshop held at the Sixth European Conference on Artificial Life in Prague and features individual contributions from the workshop's eight speakers, plus a section designed to reflect the debates that took place during the workshop's discussion sessions. The major theme that emerged during these sessions was the identity and status of artificial life as a scientific endeavor.

Cybernetics↗