143 resultados para population based incremental learning (PBIL) method
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This paper reports on an ongoing, multiphase, project-based action learning and research project. In particular, it summarizes some aspects of the learning climate and outcomes for a case study company In the software industry, Using a participatory action research approach, the learning company framework developed by Pedler et al, (1997) is used to initiate critical reflection in the company at three levels: managing director, senior management team and technical and professional staff. As such, this is one of the first systematic attempts to apply this framework to the entire organization and to a company in the knowledge-based learning economy. Two sets of issues are of general concern to the company: internal issues surrounding the company's reward and recognition policies and practices and the provision of accounting and control information in a business relevant way to all levels of staff; and external issues concerning the extent to which the company and its members actively learn from other companies and effectively capture, disseminate and use information accessed by staff in boundary-spanning roles. The paper concludes with some illustrations of changes being introduced by the company as a result of the feedback on and discussion of these issues.
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The viscosity of ionic liquids (ILs) has been modeled as a function of temperature and at atmospheric pressure using a new method based on the UNIFAC–VISCO method. This model extends the calculations previously reported by our group (see Zhao et al. J. Chem. Eng. Data 2016, 61, 2160–2169) which used 154 experimental viscosity data points of 25 ionic liquids for regression of a set of binary interaction parameters and ion Vogel–Fulcher–Tammann (VFT) parameters. Discrepancies in the experimental data of the same IL affect the quality of the correlation and thus the development of the predictive method. In this work, mathematical gnostics was used to analyze the experimental data from different sources and recommend one set of reliable data for each IL. These recommended data (totally 819 data points) for 70 ILs were correlated using this model to obtain an extended set of binary interaction parameters and ion VFT parameters, with a regression accuracy of 1.4%. In addition, 966 experimental viscosity data points for 11 binary mixtures of ILs were collected from literature to establish this model. All the binary data consist of 128 training data points used for the optimization of binary interaction parameters and 838 test data points used for the comparison of the pure evaluated values. The relative average absolute deviation (RAAD) for training and test is 2.9% and 3.9%, respectively.
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AIMS/HYPOTHESIS: To determine if vaccinations and infections are associated with the subsequent risk of Type I (insulin-dependent) diabetes mellitus in childhood. METHOD: Seven centres in Europe with access to population-based registers of children with Type I diabetes diagnosed under 15 years of age participated in a case-control study of environmental risk factors. Control children were chosen at random in each centre either from population registers or from schools and policlinics. Data on maternal and neonatal infections, common childhood infections and vaccinations were obtained for 900 cases and 2302 control children from hospital and clinic records and from parental responses to a questionnaire or interview. RESULTS: Infections early in the child's life noted in the hospital record were found to be associated with an increased risk of diabetes, although the odds ratio of 1.61 (95% confidence limits 1.11, 2.33) was significant only after adjustment for confounding variables. None of the common childhood infectious diseases was found to be associated with diabetes and neither was there evidence that any common childhood vaccination modified the risk of diabetes. Pre-school day-care attendance, a proxy measure for total infectious disease exposure in early childhood, was found, however, to be inversely associated with diabetes, with a pooled odds ratio of 0.59 (95% confidence limits 0.46, 0.76) after adjustment for confounding variables. CONCLUSION/INTERPRETATION: It seems likely that the explanation for these contrasting findings of an increased risk associated with perinatal infections coupled with a protective effect of pre-school day care lies in the age-dependent modifying influence of infections on the developing immune system.
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Evidence is unclear as to whether there is a socio-economic gradient in cerebral palsy (CP) prevalence beyond what would be expected from the socio-economic gradient for low birthweight, a strong risk factor for CP. We conducted a population-based study in five regions of the UK with CP registers, to investigate the relationship between CP prevalence and socio-economic deprivation, and how it varies by region, by birthweight and by severity and type of CP. The total study population was 1 657 569 livebirths, born between 1984 and 1997. Wards of residence were classified into five quintiles according to a census-based deprivation index, from Q1 (least deprived) to Q5 (most deprived). Socio-economic gradients were modelled by Poisson regression, and region-specific estimates combined by meta-analysis.
The prevalence of postneonatally acquired CP was 0.14 per 1000 livebirths overall. The mean deprivation gradient, expressed as the relative risk in the most deprived vs. the least deprived quintile, was 1.86 (95% confidence interval [95% CI 1.19, 2.88]). The prevalence of non-acquired CP was 2.22 per 1000 livebirths. For non-acquired CP the gradient was 1.16 [95% CI 1.00, 1.35]. Evidence for a socio-economic gradient was strongest for spastic bilateral cases (1.32 [95% CI 1.09, 1.59]) and cases with severe intellectual impairment (1.59 [95% CI 1.06, 2.39]). There was evidence for differences in gradient between regions. The gradient of risk of CP among normal birthweight births was not statistically significant overall (1.21 [95% CI 0.95, 1.54]), but was significant in two regions. There was non-significant evidence of a reduction in gradients over time.
The reduction of the higher rates of postneonatally acquired CP in the more socioeconomically deprived areas is a clear goal for prevention. While we found evidence for a socio-economic gradient for non-acquired CP of antenatal or perinatal origin, the picture was not consistent across regions, and there was some evidence of a decline in inequalities over time. The steeper gradients in some regions for normal birthweight cases and cases with severe intellectual impairment require further investigation.
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This paper describes the development of a novel metaheuristic that combines an electromagnetic-like mechanism (EM) and the great deluge algorithm (GD) for the University course timetabling problem. This well-known timetabling problem assigns lectures to specific numbers of timeslots and rooms maximizing the overall quality of the timetable while taking various constraints into account. EM is a population-based stochastic global optimization algorithm that is based on the theory of physics, simulating attraction and repulsion of sample points in moving toward optimality. GD is a local search procedure that allows worse solutions to be accepted based on some given upper boundary or ‘level’. In this paper, the dynamic force calculated from the attraction-repulsion mechanism is used as a decreasing rate to update the ‘level’ within the search process. The proposed method has been applied to a range of benchmark university course timetabling test problems from the literature. Moreover, the viability of the method has been tested by comparing its results with other reported results from the literature, demonstrating that the method is able to produce improved solutions to those currently published. We believe this is due to the combination of both approaches and the ability of the resultant algorithm to converge all solutions at every search process.
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Computational modelling is becoming ever more important for obtaining regulatory approval for new medical devices. An accepted approach is to infer performance in a population from an analysis conducted for an idealised or ‘average’ patient; we present here a method for predicting the performance of an orthopaedic implant when released into a population—effectively simulating a clinical trial. Specifically we hypothesise that an analysis based on a method for predicting the performance in a population will lead to different conclusions than an analysis based on an idealised or ‘average’ patient. To test this hypothesis we use a finite element model of an intramedullary implant in a bone whose size and remodelling activity is different for each individual in the population. We compare the performance of a low Young’s modulus implant (View the MathML source) to one with a higher Young’s modulus (200 GPa). Cyclic loading is applied and failure is assumed when the migration of the implant relative to the bone exceeds a threshold magnitude. The analysis for an idealised of ‘average’ patient predicts that the lower modulus device survives longer whereas the analysis simulating a clinical trial predicts no statistically-significant tendency (p=0.77) for the low modulus device to perform better. It is concluded that population-based simulations of implant performance–simulating a clinical trial–present a very valuable opportunity for more realistic computational pre-clinical testing of medical devices.
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Background: Interest in the prevention of osteoporosis is increasing and thus there is a need for an acceptable osteoporosis prevention programme in general practice. AIM. A study was undertaken to identify a cohort of middle-aged women attending a general practice who would be eligible for a longitudinal study looking at bone mineral density, osteoporosis and the effectiveness of hormone replacement therapy. This study aimed to describe the relationship between medical and lifestyle risk factors for osteoporosis and the initial bone density measurements in this group of women. METHOD. A health visitor administered a questionnaire to women aged between 48 and 52 years registered with a Belfast general practice. The main outcome measures were menopausal status, presence of medical and lifestyle risk factors and bone mineral density measurements. RESULTS. A total of 358 women our of 472 (76%) took part in the study which was conducted in 1991 and 1992. A highly significant difference was found between the mean bone mineral density of premenopausal, menopausal and postmenopausal women within the narrow study age range, postmenopausal women having the lowest bone mineral density. A significant relationship was found between body mass index and bone mineral density, a greater bone mineral density being found among women with a higher body mass index. Risk factors such as smoking and sedentary lifestyle were common (reported by approximately one third of respondents) but a poor relationship was found between these two and all the other risk factors and bone mineral density in this age group. CONCLUSION. Risk of osteoporosis cannot be identified by the presence of risk factors in women aged between 48 and 52 years. In terms of a current prevention strategy for general practice it would be better to take a population-based approach except for those women known to be at high risk of osteoporosis: women with early menopause or those who have had an oophorectomy.
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Aim This study aimed to document developments in rectal cancer services in a UK population and evaluate changes in outcome over a 10-year period.
Method Patients diagnosed with primary rectal carcinoma in 1996, 2001 and 2006 were identified by the Northern Ireland Cancer Registry. Data were retrospectively collected on presentation, investigation, treatment and staging. Differences over the period were analysed using the chi-squared test; Kaplan–Meier and Cox regression tests were used for survival analysis.
Results After exclusions there were 636 patients, including 187 presenting in 1996, 203 in 2001 and 246 in 2006. The use of preoperative MRI of the rectum, endorectal ultrasound and abdominal CT increased during the study period. For patients treated by surgery, total mesorectal excision (TME) increased from 19% in 1996 to 64% in 2006 (P < 0.001). The use of radiotherapy (27% in 1996, 47% in 2006) and chemotherapy (21% in 1996, 32% in 2006) increased. The overall 5-year survival improved significantly between 1996 and 2006 from 34% in 1996 to 45% in 2006 (P = 0.02). Among patients having surgery, 5-year survival increased from 43% in 1996 to 63% in 2006 (P < 0.001). Multivariate analysis showed that the improvement in survival was associated with TME and chemotherapy, while radiotherapy was not.
Conclusion Survival of patients with rectal cancer in Northern Ireland has improved significantly over the last decade, probably due to the increased use of TME and chemotherapy.
Keywords Surgery, rectum, oncology
What does this paper add to the literature?
This population-based study demonstrates a significant improvement in survival over recent years of rectal cancer patients in Northern Ireland. It concludes that surgical resection with TME and chemotherapy have had a significant impact on survival and that the improvement was not due to a stage-migration effect.
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Cooling and sinking of dense saline water in the Norwegian–Greenland Sea is essential for the formation of North Atlantic Deep Water. The convection in the Norwegian–Greenland Sea allows for a northward flow of warm surface water and southward transport of cold saline water. This circulation system is highly sensitive to climate change and has been shown to operate in different modes. In ice cores the last glacial period is characterized by millennial-scale Dansgaard–Oeschger (D–O) events of warm interstadials and cold stadials. Similar millennial-scale variability (linked to D–O events) is evident from oceanic cores, suggesting a strong coupling of the atmospheric and oceanic circulations system. Particularly long-lasting cold stadials correlate with North Atlantic Heinrich events, where icebergs released from the continents caused a spread of meltwater over the northern North Atlantic and Nordic seas. The meltwater layer is believed to have caused a stop or near-stop in the deep convection, leading to cold climate. The spreading of meltwater and changes in oceanic circulation have a large influence on the carbon exchange between atmosphere and the deep ocean and lead to profound changes in the 14C activity of the surface ocean. Here we demonstrate marine 14C reservoir ages (R) of up to c. 2000 years for Heinrich event H4. Our R estimates are based on a new method for age model construction using identified tephra layers and tie-points based on abrupt interstadial warmings.
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Haematological malignancies (HM) represent over 6% of the total cancer incidence in Europe and affect all ages, ranging between 45% of all cancers in children and 7% in the elderly. Thirty per cent of childhood cancer deaths are due to HM, 8% in the elderly. Their registration presents specific challenges, mainly because HM may transform or progress in the course of the disease into other types of HM. In the context of cancer registration decisions have to be made about classifying subsequent notifications on the same patient as the same tumour (progression), a transformation or a new tumour registration. Allocation of incidence date and method of diagnosis must also be standardised. We developed European Network of Cancer Registries (ENCR) recommendations providing specific advice for cancer registries to use haematology and molecular laboratories as data sources, conserve the original date of incidence in case of change of diagnosis, make provision for recording both the original as well as transformed tumour and to apply precise rules for recording and counting multiple diagnoses. A reference table advising on codes which reflect a potential transformation or a new tumour is included. This work will help to improve comparability of data produced by population-based cancer registries, which are indispensable for aetiological research, health care planning and clinical research, an increasing important area with the application of targeted therapies.
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Background: Hirschsprung's disease is a congenital gut motility disorder, characterised by the absence of the enteric ganglion cells along the distal gut. The aim of this study was to describe the epidemiology of Hirschsprung's disease, including additional congenital anomalies, total prevalence, trends, and association with maternal age. Methods: Cases of Hirschsprung's disease delivered during 1980 to 2009 notified to 31 European Surveillance of Congenital Anomaly registers formed the population-based case-series. Prevalence rates and 95% confidence intervals were calculated as the number of cases per 10,000 births. Multilevel Poisson regression was performed to investigate trends in prevalence, geographical variation and the association with maternal age. Results: There were 1,322 cases of Hirschsprung's disease among 12,146,210 births. The total prevalence was 1.09 (95% confidence interval, 1.03–1.15) per 10,000 births and there was a small but significant increase in prevalence over time (relative risk = 1.01; 95% credible interval, 1.00–1.02; p = 0.004). There was evidence of geographical heterogeneity in prevalence (p < 0.001). Excluding 146 (11.0%) cases with chromosomal anomalies or genetic syndromes, there were 1,176 cases (prevalence = 0.97; 95% confidence interval, 0.91–1.03 per 10,000 births), of which 137 (11.6%) had major structural anomalies. There was no evidence of a significant increased risk of Hirschsprung's disease in cases born to women aged ≥35 years compared with those aged 25 to 29 (relative risk = 1.09; 95% credible interval, 0.91–1.31; p = 0.355). Conclusion: This large population-based study found evidence of a small increasing trend in Hirschsprung's disease and differences in prevalence by geographic location. There was also no evidence of an association with maternal age.
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Objective: Many forms of contraception are available on prescription only for example, the oral contraceptive pill (OCP) and long-acting reversible contraceptives (LARCs). In this analysis we aim to identify key determinants of prescription contraceptive use.
Design: Cross-sectional population survey. Data on sociodemographic indices, concerns about the OCP and perceived barriers to access were collected.
Setting: Data set constructed from a representative population-based telephone survey of community dwelling adults in the Republic of Ireland (RoI)
Participants: 1515 women aged between 18 and 45 years
Main outcome measure: Self-reported user of the OCP or LARCs (intrauterine contraception, contraceptive injections or subdermal contraceptive implants) in the previous 12 months.
Results: For at least some of the previous year, 35% had used the OCP and 14% had used LARCs, while 3% had used two or more of these methods. OCP users were significantly younger, more likely to be unmarried and had higher income than non-users. Overall, 68% agreed with the statement ‘that taking a break from long-term use of the contraceptive pill is a good idea’ and 37% agreed with the statement that ‘the OCP has dangerous side effects’ and this was the strongest predictor variable of non-use of the OCP. Intrauterine contraception users were significantly older, more likely to be married and had lower income than non-users. Injections or subdermal contraceptive implant users were significantly younger, less likely to be married, had lower income and were less likely to agree that taking a break from long-term use of the pill is a good idea than non-users.
Conclusions: Prescription contraceptive use is sociodemographically patterned, with LARCs in particular being associated with lower incomes in the RoI. Concerns about the safety of the OCP remain prevalent and are important and modifiable determinants of contraceptive-related behaviour.
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Importance Countries with advanced welfare systems are increasingly relying on the input of informal caregivers and there are growing concerns for their mental and physical wellbeing. However, the evidence about the relationship between caregiving and mortality risk is less clear.
Methods A census-based record linkage study with mortality follow-up of thirty-three months. A total of 1,122,779 individuals including 183,842 caregivers, of whom 28.2% (51,927) were providing fifty or more hours caregiving per week.
Results Over thirty-three months of follow-up a total of 29,335 deaths occurred, with 2,443 of these to caregivers. Mortality risk for caregivers was lower than for non-caregivers (HR= 0.72: 95%CI=0.69, 0.75 in the fully adjusted model), and the lower risk was evident even for those providing fifty or more hours of caregiving per week (adjusted Hazard Ratio=0.77: 95%CI=0.71, 0.83 and 0.76: 95%CI=0.69, 0.83 for men and women respectively). There was no evidence that this relationship varied by either age or marital status. Even amongst people with chronic health problems such as poor mental health, caregivers had lower mortality risk than non-caregivers. Caregiving is associated with reduced mortality risk for most causes - for example, the risk of death from Ischaemic Heart Disease for caregivers providing fifty or more hours was 27% and 31% lower for men and for women respectively compared to non-caregivers (HR=0.73: 95%CI=0.60, 0.88 and HR=0.69: 95%CI=0.51, 0.92).
Conclusions This large population-based study confirms that for the majority of caregivers the beneficial effects of caregiving in terms of short-term mortality risk appear to outweigh any negative effects, even amongst people with significant health problems. These results underscore the need for a reappraisal of how caregiving is perceived.
Keywords: caregiving, carers, mortality, longitudinal follow-up.
marital status. Even amongst people with chronic health problems such as poor mental health, caregivers had lower mortality risk than non-caregivers. Caregiving is associated with reduced mortality risk for most causes - for example, the risk of death from Ischaemic Heart Disease for caregivers providing fifty or more hours was 27% and 31% lower for men and for women respectively compared to non-caregivers (HR=0.73: 95%CI=0.60, 0.88 and HR=0.69: 95%CI=0.51, 0.92).
Conclusions This large population-based study confirms that for the majority of caregivers the beneficial effects of caregiving in terms of short-term mortality risk appear to outweigh any negative effects, even amongst people with significant health problems. These results underscore the need for a reappraisal of how caregiving is perceived.
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Environmental problems, especially climate change, have become a serious global issue waiting for people to solve. In the construction industry, the concept of sustainable building is developing to reduce greenhouse gas emissions. In this study, a building information modeling (BIM) based building design optimization method is proposed to facilitate designers to optimize their designs and improve buildings’ sustainability. A revised particle swarm optimization (PSO) algorithm is applied to search for the trade-off between life cycle costs (LCC) and life cycle carbon emissions (LCCE) of building designs. In order tovalidate the effectiveness and efficiency of this method, a case study of an office building is conducted in Hong Kong. The result of the case study shows that this method can enlarge the searching space for optimal design solutions and shorten the processing time for optimal design results, which is really helpful for designers to deliver an economic and environmental friendly design scheme.
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Generating timetables for an institution is a challenging and time consuming task due to different demands on the overall structure of the timetable. In this paper, a new hybrid method which is a combination of a great deluge and artificial bee colony algorithm (INMGD-ABC) is proposed to address the university timetabling problem. Artificial bee colony algorithm (ABC) is a population based method that has been introduced in recent years and has proven successful in solving various optimization problems effectively. However, as with many search based approaches, there exist weaknesses in the exploration and exploitation abilities which tend to induce slow convergence of the overall search process. Therefore, hybridization is proposed to compensate for the identified weaknesses of the ABC. Also, inspired from imperialist competitive algorithms, an assimilation policy is implemented in order to improve the global exploration ability of the ABC algorithm. In addition, Nelder–Mead simplex search method is incorporated within the great deluge algorithm (NMGD) with the aim of enhancing the exploitation ability of the hybrid method in fine-tuning the problem search region. The proposed method is tested on two differing benchmark datasets i.e. examination and course timetabling datasets. A statistical analysis t-test has been conducted and shows the performance of the proposed approach as significantly better than basic ABC algorithm. Finally, the experimental results are compared against state-of-the art methods in the literature, with results obtained that are competitive and in certain cases achieving some of the current best results to those in the literature.