The stochastic resonance for the incidence function model of metapopulation
Li, Jiang-Cheng; Dong, Zhi-Wei; Zhou, Ruo-Wei; Li, Yun-Xian; Qian, Zhen-Wei
2017-06-01
A stochastic model with endogenous and exogenous periodicities is proposed in this paper on the basis of metapopulation dynamics to model the crop yield losses due to pests and diseases. The rationale is that crop yield losses occur because the physiology of the growing crop is negatively affected by pests and diseases in a dynamic way over time as crop both grows and develops. Metapopulation dynamics can thus be used to model the resultant crop yield losses. The stochastic metapopulation process is described by using the Simplified Incidence Function model (IFM). Compared to the original IFMs, endogenous and exogenous periodicities are considered in the proposed model to handle the cyclical patterns observed in pest infestations, diseases epidemics, and exogenous affecting factors such as temperature and rainfalls. Agricultural loss data in China are used to fit the proposed model. Experimental results demonstrate that: (1) Model with endogenous and exogenous periodicities is a better fit; (2) When the internal system fluctuations and external environmental fluctuations are negatively correlated, EIL or the cost of loss is monotonically increasing; when the internal system fluctuations and external environmental fluctuations are positively correlated, an outbreak of pests and diseases might occur; (3) If the internal system fluctuations and external environmental fluctuations are positively correlated, an optimal patch size can be identified which will greatly weaken the effects of external environmental influence and hence inhibit pest infestations and disease epidemics.
Analysis of an SEIR Epidemic Model with Saturated Incidence and Saturated Treatment Function
Directory of Open Access Journals (Sweden)
Jinhong Zhang
2014-01-01
Full Text Available The dynamics of SEIR epidemic model with saturated incidence rate and saturated treatment function are explored in this paper. The basic reproduction number that determines disease extinction and disease survival is given. The existing threshold conditions of all kinds of the equilibrium points are obtained. Sufficient conditions are established for the existence of backward bifurcation. The local asymptotical stability of equilibrium is verified by analyzing the eigenvalues and using the Routh-Hurwitz criterion. We also discuss the global asymptotical stability of the endemic equilibrium by autonomous convergence theorem. The study indicates that we should improve the efficiency and enlarge the capacity of the treatment to control the spread of disease. Numerical simulations are presented to support and complement the theoretical findings.
Institute of Scientific and Technical Information of China (English)
Farah Yasmeen[1; Sidra Zaheer[2
2014-01-01
Background： Breast cancer is the most common female cancer in Pakistan. The incidence of breast cancer in Pakistan is about 2.5 times higher than that in the neighboring countries India and Iran. In Karachi, the most populated city of Pakistan, the age-standardized rate of breast cancer was 69.1 per 100,000 women during 1998-2002, which is the highest recorded rate in Asia. The carcinoma of breast in Pakistan is an enormous public health concern. In this study, we examined the recent trends of breast cancer incidence rates among the women in Karachi. Methods： We obtained the secondary data of breast cancer incidence from various hospitals. They included Jinnah Hospital, KIRAN （Karachi Institute of Radiotherapy and Nuclear Medicine）, and Civil hospital, where the data were available for the years 2004-2011. A total of 5331 new cases of female breast cancer were registered during this period. We analyzed the data in 5-year age groups 15-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, 75＋. Nonparametric smoothing were used to obtained age-specific incidence curves, and then the curves are decomposed using principal components analysis to fit FTS （functional time series） model. We then used exponential smoothing statspace models to estimate the forecasts of incidence curve and construct prediction intervals. Results： The breast cancer incidence rates in Karachi increased with age for all available years. The rates increased monotonically and are relatively sharp with the age from 15 years to 50 years and then they show variability after the age of 50 years. 10-year forecasts for the female breast cancer incidence rates in Karachi show that the future rates are expected to remain stable for the age-groups 15-50 years, but they will increase for the females of 50-years and over. Hence in future, the newly diagnosed breast cancer cases in the older women in Karachi are expected to increase. Conclusion： Prediction of age
Prevalence Incidence Mixture Models
The R package and webtool fits Prevalence Incidence Mixture models to left-censored and irregularly interval-censored time to event data that is commonly found in screening cohorts assembled from electronic health records. Absolute and relative risk can be estimated for simple random sampling, and stratified sampling (the two approaches of superpopulation and a finite population are supported for target populations). Non-parametric (absolute risks only), semi-parametric, weakly-parametric (using B-splines), and some fully parametric (such as the logistic-Weibull) models are supported.
Functional analysis of controbloc incidents
International Nuclear Information System (INIS)
Gouffon, A.; Jorel, M.
1992-11-01
The subject of the present paper is the survey jointly carried out in 1989 by the IPSN Safety Analysis Department and the Firm BERTIN and Co. on significant incidents related to the Controbloc system equipping the EDF 1300 MWe PWR power plants in France. This survey consisted in a general review of Controbloc operating problems, together with analysis of the safety consequences of the incidents discussed. The survey enabled improvements to be recommended in this respect and provided a basis for safety analysis
Widowhood Fantasies: Incidence, Characteristics, and Potential Function.
Bear, Roberta Meyer; Flowers, Barbara P.
Although some people fantasize about their spouse's possible death, the literature contains no reports of research on widowhood fantasies. The incidence, characteristics, and possible function of these fantasies were examined in individual interviews with 28 divorced and married men and women. Interview data were analyzed by calculating chi-square…
Improving Agent Based Modeling of Critical Incidents
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Robert Till
2010-04-01
Full Text Available Agent Based Modeling (ABM is a powerful method that has been used to simulate potential critical incidents in the infrastructure and built environments. This paper will discuss the modeling of some critical incidents currently simulated using ABM and how they may be expanded and improved by using better physiological modeling, psychological modeling, modeling the actions of interveners, introducing Geographic Information Systems (GIS and open source models.
Dynamic prediction of cumulative incidence functions by direct binomial regression.
Grand, Mia K; de Witte, Theo J M; Putter, Hein
2018-03-25
In recent years there have been a series of advances in the field of dynamic prediction. Among those is the development of methods for dynamic prediction of the cumulative incidence function in a competing risk setting. These models enable the predictions to be updated as time progresses and more information becomes available, for example when a patient comes back for a follow-up visit after completing a year of treatment, the risk of death, and adverse events may have changed since treatment initiation. One approach to model the cumulative incidence function in competing risks is by direct binomial regression, where right censoring of the event times is handled by inverse probability of censoring weights. We extend the approach by combining it with landmarking to enable dynamic prediction of the cumulative incidence function. The proposed models are very flexible, as they allow the covariates to have complex time-varying effects, and we illustrate how to investigate possible time-varying structures using Wald tests. The models are fitted using generalized estimating equations. The method is applied to bone marrow transplant data and the performance is investigated in a simulation study. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Incident Duration Modeling Using Flexible Parametric Hazard-Based Models
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Ruimin Li
2014-01-01
Full Text Available Assessing and prioritizing the duration time and effects of traffic incidents on major roads present significant challenges for road network managers. This study examines the effect of numerous factors associated with various types of incidents on their duration and proposes an incident duration prediction model. Several parametric accelerated failure time hazard-based models were examined, including Weibull, log-logistic, log-normal, and generalized gamma, as well as all models with gamma heterogeneity and flexible parametric hazard-based models with freedom ranging from one to ten, by analyzing a traffic incident dataset obtained from the Incident Reporting and Dispatching System in Beijing in 2008. Results show that different factors significantly affect different incident time phases, whose best distributions were diverse. Given the best hazard-based models of each incident time phase, the prediction result can be reasonable for most incidents. The results of this study can aid traffic incident management agencies not only in implementing strategies that would reduce incident duration, and thus reduce congestion, secondary incidents, and the associated human and economic losses, but also in effectively predicting incident duration time.
Predicting Cumulative Incidence Probability: Marginal and Cause-Specific Modelling
DEFF Research Database (Denmark)
Scheike, Thomas H.; Zhang, Mei-Jie
2005-01-01
cumulative incidence probability; cause-specific hazards; subdistribution hazard; binomial modelling......cumulative incidence probability; cause-specific hazards; subdistribution hazard; binomial modelling...
Pelvic incidence variation among individuals: functional influence versus genetic determinism.
Chen, Hong-Fang; Zhao, Chang-Qing
2018-03-20
Pelvic incidence has become one of the most important sagittal parameters in spinal surgery. Despite its great importance, pelvic incidence can vary from 33° to 85° in the normal population. The reasons for this great variability in pelvic incidence remain unexplored. The objective of this article is to present some possible interpretations for the great variability in pelvic incidence under both normal and pathological conditions and to further understand the determinants of pelvic incidence from the perspective of the functional requirements for bipedalism and genetic backgrounds via a literature review. We postulate that both pelvic incidence and pelvic morphology may be genetically predetermined, and a great variability in pelvic incidence may already exist even before birth. This great variability may also serve as a further reminder that the sagittal profile, bipedal locomotion mode, and genetic background of every individual are unique and specific, and clinicians should avoid making universally applying broad generalizations of pelvic incidence. Although PI is an important parameter and there are many theories behind its variability, we still do not have clear mechanistic answers.
Sensory and Motor Peripheral Nerve Function and Incident Mobility Disability
DEFF Research Database (Denmark)
Ward, R. E.; Boudreau, R. M.; Caserotti, P.
2014-01-01
ObjectivesTo assess the relationship between sensorimotor nerve function and incident mobility disability over 10years. DesignProspective cohort study with longitudinal analysis. SettingTwo U.S. clinical sites. ParticipantsPopulation-based sample of community-dwelling older adults with no mobility...
Mori, Kentaro; Kaiho, Yu; Tomata, Yasutake; Narita, Mamoru; Tanji, Fumiya; Sugiyama, Kemmyo; Sugawara, Yumi; Tsuji, Ichiro
2017-04-01
To test the hypothesis that elderly persons who feel ikigai (a sense of life worth living) have a lower risk of incident functional disability than those who do not. Recent studies have suggested that ikigai impacts on mortality. However, its impact upon disability is unknown. The aim of the present study was to investigate the association between ikigai and incident functional disability among elderly persons. We conducted a prospective cohort study of 830 Japanese elderly persons aged ≥70 years as a comprehensive geriatric assessment in 2003. Information on ikigai was collected by self-reported questionnaire. Data on functional disability were retrieved from the public Long-term Care Insurance database in which participants were followed up for 11 years. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incidence of functional disability were calculated for three groups delineated according to the presence of ikigai (“no”, “uncertain” or “yes”) using the Cox proportional hazards regression model. The 11-year incidence of functional disability was 53.3% (442 cases). As compared with the “no” group, the multiple-adjusted HR (95% CI) of incident functional disability was 0.61 (0.36–1.02) for the “uncertain” group and 0.50 (0.30–0.84) for the “yes” group. A stronger degree of ikigai is significantly associated with a lower risk of incident functional disability. Copyright © 2017 Elsevier Inc. All rights reserved.
Phenomenological modelling of second cancer incidence for radiation treatment planning
International Nuclear Information System (INIS)
Pfaffenberger, Asja; Oelfke, Uwe; Schneider, Uwe; Poppe, Bjoern
2009-01-01
It is still an unanswered question whether a relatively low dose of radiation to a large volume or a higher dose to a small volume produces the higher cancer incidence. This is of interest in view of modalities like IMRT or rotation therapy where high conformity to the target volume is achieved at the cost of a large volume of normal tissue exposed to radiation. Knowledge of the shape of the dose response for radiation-induced cancer is essential to answer the question of what risk of second cancer incidence is implied by which treatment modality. This study therefore models the dose response for radiation-induced second cancer after radiation therapy of which the exact mechanisms are still unknown. A second cancer risk estimation tool for treatment planning is presented which has the potential to be used for comparison of different treatment modalities, and risk is estimated on a voxel basis for different organs in two case studies. The presented phenomenological model summarises the impact of microscopic biological processes into effective parameters of mutation and cell sterilisation. In contrast to other models, the effective radiosensitivities of mutated and non-mutated cells are allowed to differ. Based on the number of mutated cells present after irradiation, the model is then linked to macroscopic incidence by summarising model parameters and modifying factors into natural cancer incidence and the dose response in the lower-dose region. It was found that all principal dose-response functions discussed in the literature can be derived from the model. However, from the investigation and due to scarcity of adequate data, rather vague statements about likelihood of dose-response functions can be made than a definite decision for one response. Based on the predicted model parameters, the linear response can probably be rejected using the dynamics described, but both a flattening response and a decrease appear likely, depending strongly on the effective cell
Dynamic Tax Incidence in a Finite Horizon Model
Itaya, Jun-ichi
1992-01-01
This paper reexamines the problem of long-run tax incidence by using a two-sector growth model in which finitely-lived individuals undertake intertemporal optimizing decisions in the presence of annuity markets. Under a constant relative risk aversion utility function, none of the selective taxes imposed on the consumption goods sector are neutral with respect to the long-run wage/profit ratio even if labor supply is fixed. This result differs significantly both from that of the infinite hori...
Estimating cardiovascular disease incidence from prevalence: a spreadsheet based model
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Xue Feng Hu
2017-01-01
Full Text Available Abstract Background Disease incidence and prevalence are both core indicators of population health. Incidence is generally not as readily accessible as prevalence. Cohort studies and electronic health record systems are two major way to estimate disease incidence. The former is time-consuming and expensive; the latter is not available in most developing countries. Alternatively, mathematical models could be used to estimate disease incidence from prevalence. Methods We proposed and validated a method to estimate the age-standardized incidence of cardiovascular disease (CVD, with prevalence data from successive surveys and mortality data from empirical studies. Hallett’s method designed for estimating HIV infections in Africa was modified to estimate the incidence of myocardial infarction (MI in the U.S. population and incidence of heart disease in the Canadian population. Results Model-derived estimates were in close agreement with observed incidence from cohort studies and population surveillance systems. This method correctly captured the trend in incidence given sufficient waves of cross-sectional surveys. The estimated MI declining rate in the U.S. population was in accordance with the literature. This method was superior to closed cohort, in terms of the estimating trend of population cardiovascular disease incidence. Conclusion It is possible to estimate CVD incidence accurately at the population level from cross-sectional prevalence data. This method has the potential to be used for age- and sex- specific incidence estimates, or to be expanded to other chronic conditions.
[Application of ARIMA model on prediction of malaria incidence].
Jing, Xia; Hua-Xun, Zhang; Wen, Lin; Su-Jian, Pei; Ling-Cong, Sun; Xiao-Rong, Dong; Mu-Min, Cao; Dong-Ni, Wu; Shunxiang, Cai
2016-01-29
To predict the incidence of local malaria of Hubei Province applying the Autoregressive Integrated Moving Average model (ARIMA). SPSS 13.0 software was applied to construct the ARIMA model based on the monthly local malaria incidence in Hubei Province from 2004 to 2009. The local malaria incidence data of 2010 were used for model validation and evaluation. The model of ARIMA (1, 1, 1) (1, 1, 0) 12 was tested as relatively the best optimal with the AIC of 76.085 and SBC of 84.395. All the actual incidence data were in the range of 95% CI of predicted value of the model. The prediction effect of the model was acceptable. The ARIMA model could effectively fit and predict the incidence of local malaria of Hubei Province.
A new, accurate predictive model for incident hypertension
DEFF Research Database (Denmark)
Völzke, Henry; Fung, Glenn; Ittermann, Till
2013-01-01
Data mining represents an alternative approach to identify new predictors of multifactorial diseases. This work aimed at building an accurate predictive model for incident hypertension using data mining procedures.......Data mining represents an alternative approach to identify new predictors of multifactorial diseases. This work aimed at building an accurate predictive model for incident hypertension using data mining procedures....
Scrub Typhus Incidence Modeling with Meteorological Factors in South Korea.
Kwak, Jaewon; Kim, Soojun; Kim, Gilho; Singh, Vijay P; Hong, Seungjin; Kim, Hung Soo
2015-06-29
Since its recurrence in 1986, scrub typhus has been occurring annually and it is considered as one of the most prevalent diseases in Korea. Scrub typhus is a 3rd grade nationally notifiable disease that has greatly increased in Korea since 2000. The objective of this study is to construct a disease incidence model for prediction and quantification of the incidences of scrub typhus. Using data from 2001 to 2010, the incidence Artificial Neural Network (ANN) model, which considers the time-lag between scrub typhus and minimum temperature, precipitation and average wind speed based on the Granger causality and spectral analysis, is constructed and tested for 2011 to 2012. Results show reliable simulation of scrub typhus incidences with selected predictors, and indicate that the seasonality in meteorological data should be considered.
Scrub Typhus Incidence Modeling with Meteorological Factors in South Korea
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Jaewon Kwak
2015-06-01
Full Text Available Since its recurrence in 1986, scrub typhus has been occurring annually and it is considered as one of the most prevalent diseases in Korea. Scrub typhus is a 3rd grade nationally notifiable disease that has greatly increased in Korea since 2000. The objective of this study is to construct a disease incidence model for prediction and quantification of the incidences of scrub typhus. Using data from 2001 to 2010, the incidence Artificial Neural Network (ANN model, which considers the time-lag between scrub typhus and minimum temperature, precipitation and average wind speed based on the Granger causality and spectral analysis, is constructed and tested for 2011 to 2012. Results show reliable simulation of scrub typhus incidences with selected predictors, and indicate that the seasonality in meteorological data should be considered.
Molnar, Amber O; Eddeen, Anan Bader; Ducharme, Robin; Garg, Amit X; Harel, Ziv; McCallum, Megan K; Perl, Jeffrey; Wald, Ron; Zimmerman, Deborah; Sood, Manish M
2017-07-06
Early evidence suggests proteinuria is independently associated with incident atrial fibrillation (AF). We sought to investigate whether the association of proteinuria with incident AF is altered by kidney function. Retrospective cohort study using administrative healthcare databases in Ontario, Canada (2002-2015). A total of 736 666 patients aged ≥40 years not receiving dialysis and with no previous history of AF were included. Proteinuria was defined using the urine albumin-to-creatinine ratio (ACR) and kidney function by the estimated glomerular filtration rate (eGFR). The primary outcome was time to AF. Cox proportional models were used to determine the hazard ratio for AF censored for death, dialysis, kidney transplant, or end of follow-up. Fine and Grey models were used to determine the subdistribution hazard ratio for AF, with death as a competing event. Median follow-up was 6 years and 44 809 patients developed AF. In adjusted models, ACR and eGFR were associated with AF ( P kidney function (ACR × eGFR interaction, P kidney function (adjusted hazard ratios, 4.5 [95% CI, 4.0-5.1] and 2.6 [95% CI, 2.4-2.8], respectively; referent ACR 0 and eGFR 120). Results were similar in competing risk analyses. Proteinuria increases the risk of incident AF markedly in patients with intact kidney function compared with those with decreased kidney function. Screening and preventative strategies should consider proteinuria as an independent risk factor for AF. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.
Nonparametric Transfer Function Models
Liu, Jun M.; Chen, Rong; Yao, Qiwei
2009-01-01
In this paper a class of nonparametric transfer function models is proposed to model nonlinear relationships between ‘input’ and ‘output’ time series. The transfer function is smooth with unknown functional forms, and the noise is assumed to be a stationary autoregressive-moving average (ARMA) process. The nonparametric transfer function is estimated jointly with the ARMA parameters. By modeling the correlation in the noise, the transfer function can be estimated more efficiently. The parsimonious ARMA structure improves the estimation efficiency in finite samples. The asymptotic properties of the estimators are investigated. The finite-sample properties are illustrated through simulations and one empirical example. PMID:20628584
Complex dynamics of an SEIR epidemic model with saturated incidence rate and treatment
Khan, Muhammad Altaf; Khan, Yasir; Islam, Saeed
2018-03-01
In this paper, we describe the dynamics of an SEIR epidemic model with saturated incidence, treatment function, and optimal control. Rigorous mathematical results have been established for the model. The stability analysis of the model is investigated and found that the model is locally asymptotically stable when R0 1. The proposed model may possess a backward bifurcation. The optimal control problem is designed and obtained their necessary results. Numerical results have been presented for justification of theoretical results.
Krefis, Anne Caroline; Schwarz, Norbert Georg; Krüger, Andreas; Fobil, Julius; Nkrumah, Bernard; Acquah, Samuel; Loag, Wibke; Sarpong, Nimako; Adu-Sarkodie, Yaw; Ranft, Ulrich; May, Jürgen
2011-02-01
Climatic factors influence the incidence of vector-borne diseases such as malaria. They modify the abundance of mosquito populations, the length of the extrinsic parasite cycle in the mosquito, the malarial dynamics, and the emergence of epidemics in areas of low endemicity. The objective of this study was to investigate temporal associations between weekly malaria incidence in 1,993 children < 15 years of age and weekly rainfall. A time series analysis was conducted by using cross-correlation function and autoregressive modeling. The regression model showed that the level of rainfall predicted the malaria incidence after a time lag of 9 weeks (mean = 60 days) and after a time lag between one and two weeks. The analyses provide evidence that high-resolution precipitation data can directly predict malaria incidence in a highly endemic area. Such models might enable the development of early warning systems and support intervention measures.
Asymmetric diffusion model for oblique-incidence reflectometry
Institute of Scientific and Technical Information of China (English)
Yaqin Chen; Liji Cao; Liqun Sun
2011-01-01
A diffusion theory model induced by a line source distribution is presented for oblique-incidence reflectom-etry. By fitting to this asymmetric diffusion model, the absorption and reduced scattering coefficients μa and μ's of the turbid medium can both be determined with accuracy of 10% from the absolute profile of the diffuse reflectance in the incident plane at the negative position -1.5 transport mean free path (mfp') away from the incident point; particularly, μ's can be estimated from the data at positive positions within 0-1.0 mfp' with 10% accuracy. The method is verified by Monte Carlo simulations and experimentally tested on a phantom.%A diffusion theory model induced by a line source distribution is presented for oblique-incidence reflectometry.By fitting to this asymmetric diffusion model,the absorption and reduced scattering coefficients μa and μ's of the turbid medium can both be determined with accuracy of 10％ from the absolute profile of the diffuse reflectance in the incident plane at the negative position -1.5 transport mean free path (mfp')away from the incident point;particularly,μ's can be estimated from the data at positive positions within 0-1.0 mfp' with 10％ accuracy.The method is verified by Monte Carlo simulations and experimentally tested on a phantom.Knowledge about the optical properties,including the absorption coefficient (μa) and the reduced scattering coefficient (μ's =μs(1-g)),where μs is the scattering coefficient and g is the anisotropy factor of scattering,of biological tissues plays an important role for optical therapeutic and diagnostic techniques in medicine.
Ferree, Steven; van der Vliet, Quirine M J; van Heijl, Mark; Houwert, Roderick M; Leenen, Luke P H; Hietbrink, Falco
INTRODUCTION: Injuries of the hand can cause significant functional impairment, diminished quality of life and delayed return to work. However, the incidence and functional outcome of hand injuries in polytrauma patients is currently unknown. The aim of this study was to determine the incidence,
Accident Analysis and Barrier Function (AEB) Method. Manual for Incident Analysis
Energy Technology Data Exchange (ETDEWEB)
Svenson, Ola [Stockholm Univ. (Sweden). Dept. of Psychology
2000-02-01
The Accident Analysis and Barrier Function (AEB) Method models an accident or incident as a series of interactions between human and technical systems. In the sequence of human and technical errors leading to an accident there is, in principle, a possibility to arrest the development between each two successive errors. This can be done by a barrier function which, for example, can stop an operator from making an error. A barrier function can be performed by one or several barrier function systems. To illustrate, a mechanical system, a computer system or another operator can all perform a given barrier function to stop an operator from making an error. The barrier function analysis consists of analysis of suggested improvements, the effectiveness of the improvements, the costs of implementation, probability of implementation, the cost of maintaining the barrier function, the probability that maintenance will be kept up to standards and the generalizability of the suggested improvement. The AEB method is similar to the US method called HPES, but differs from that method in different ways. To exemplify, the AEB method has more emphasis on technical errors than HPES. In contrast to HPES that describes a series of events, the AEB method models only errors. This gives a more focused analysis making it well suited for checking other HPES-type accident analyses. However, the AEB method is a generic and stand-alone method that has been applied in other fields than nuclear power, such as, in traffic accident analyses.
Accident Analysis and Barrier Function (AEB) Method. Manual for Incident Analysis
International Nuclear Information System (INIS)
Svenson, Ola
2000-02-01
The Accident Analysis and Barrier Function (AEB) Method models an accident or incident as a series of interactions between human and technical systems. In the sequence of human and technical errors leading to an accident there is, in principle, a possibility to arrest the development between each two successive errors. This can be done by a barrier function which, for example, can stop an operator from making an error. A barrier function can be performed by one or several barrier function systems. To illustrate, a mechanical system, a computer system or another operator can all perform a given barrier function to stop an operator from making an error. The barrier function analysis consists of analysis of suggested improvements, the effectiveness of the improvements, the costs of implementation, probability of implementation, the cost of maintaining the barrier function, the probability that maintenance will be kept up to standards and the generalizability of the suggested improvement. The AEB method is similar to the US method called HPES, but differs from that method in different ways. To exemplify, the AEB method has more emphasis on technical errors than HPES. In contrast to HPES that describes a series of events, the AEB method models only errors. This gives a more focused analysis making it well suited for checking other HPES-type accident analyses. However, the AEB method is a generic and stand-alone method that has been applied in other fields than nuclear power, such as, in traffic accident analyses
The proportional odds cumulative incidence model for competing risks
DEFF Research Database (Denmark)
Eriksson, Frank; Li, Jianing; Scheike, Thomas
2015-01-01
We suggest an estimator for the proportional odds cumulative incidence model for competing risks data. The key advantage of this model is that the regression parameters have the simple and useful odds ratio interpretation. The model has been considered by many authors, but it is rarely used...... in practice due to the lack of reliable estimation procedures. We suggest such procedures and show that their performance improve considerably on existing methods. We also suggest a goodness-of-fit test for the proportional odds assumption. We derive the large sample properties and provide estimators...
Monte Carlo calculations of ligth-ion sputtering as a function of the incident angle
International Nuclear Information System (INIS)
Haggmark, L.G.; Biersack, J.P.
1980-01-01
The sputtering of metal surfaces by light ions has been studied as a function of the incident angle using an extension of the TRIM Monte Carlo computer program. Sputtering yields were calculated at both normal and oblique angles of incidence for H, D, T, and 4 He impinging on Ni, Mo, and Au targets with energies <= 10 keV. Direct comparisons are made with the most recent experimental and theoretical results. There is generally good agreement with the experimental data although our calculated maximum in the yield usually occurs at a smaller incident angle, measured from the surface normal. The enhancement of the yield at large incident angles over that at normal incidence is observed to be a complex function of the incident ion's energy and mass and the target's atomic weight and surface binding energy. (orig.)
Prediction Model for Gastric Cancer Incidence in Korean Population.
Directory of Open Access Journals (Sweden)
Bang Wool Eom
Full Text Available Predicting high risk groups for gastric cancer and motivating these groups to receive regular checkups is required for the early detection of gastric cancer. The aim of this study is was to develop a prediction model for gastric cancer incidence based on a large population-based cohort in Korea.Based on the National Health Insurance Corporation data, we analyzed 10 major risk factors for gastric cancer. The Cox proportional hazards model was used to develop gender specific prediction models for gastric cancer development, and the performance of the developed model in terms of discrimination and calibration was also validated using an independent cohort. Discrimination ability was evaluated using Harrell's C-statistics, and the calibration was evaluated using a calibration plot and slope.During a median of 11.4 years of follow-up, 19,465 (1.4% and 5,579 (0.7% newly developed gastric cancer cases were observed among 1,372,424 men and 804,077 women, respectively. The prediction models included age, BMI, family history, meal regularity, salt preference, alcohol consumption, smoking and physical activity for men, and age, BMI, family history, salt preference, alcohol consumption, and smoking for women. This prediction model showed good accuracy and predictability in both the developing and validation cohorts (C-statistics: 0.764 for men, 0.706 for women.In this study, a prediction model for gastric cancer incidence was developed that displayed a good performance.
A new, accurate predictive model for incident hypertension.
Völzke, Henry; Fung, Glenn; Ittermann, Till; Yu, Shipeng; Baumeister, Sebastian E; Dörr, Marcus; Lieb, Wolfgang; Völker, Uwe; Linneberg, Allan; Jørgensen, Torben; Felix, Stephan B; Rettig, Rainer; Rao, Bharat; Kroemer, Heyo K
2013-11-01
Data mining represents an alternative approach to identify new predictors of multifactorial diseases. This work aimed at building an accurate predictive model for incident hypertension using data mining procedures. The primary study population consisted of 1605 normotensive individuals aged 20-79 years with 5-year follow-up from the population-based study, that is the Study of Health in Pomerania (SHIP). The initial set was randomly split into a training and a testing set. We used a probabilistic graphical model applying a Bayesian network to create a predictive model for incident hypertension and compared the predictive performance with the established Framingham risk score for hypertension. Finally, the model was validated in 2887 participants from INTER99, a Danish community-based intervention study. In the training set of SHIP data, the Bayesian network used a small subset of relevant baseline features including age, mean arterial pressure, rs16998073, serum glucose and urinary albumin concentrations. Furthermore, we detected relevant interactions between age and serum glucose as well as between rs16998073 and urinary albumin concentrations [area under the receiver operating characteristic (AUC 0.76)]. The model was confirmed in the SHIP validation set (AUC 0.78) and externally replicated in INTER99 (AUC 0.77). Compared to the established Framingham risk score for hypertension, the predictive performance of the new model was similar in the SHIP validation set and moderately better in INTER99. Data mining procedures identified a predictive model for incident hypertension, which included innovative and easy-to-measure variables. The findings promise great applicability in screening settings and clinical practice.
An SIRS model with a nonlinear incidence rate
International Nuclear Information System (INIS)
Jin Yu; Wang, Wendi; Xiao Shiwu
2007-01-01
The global dynamics of an SIRS model with a nonlinear incidence rate is investigated. We establish a threshold for a disease to be extinct or endemic, analyze the existence and asymptotic stability of equilibria, and verify the existence of bistable states, i.e., a stable disease free equilibrium and a stable endemic equilibrium or a stable limit cycle. In particular, we find that the model admits stability switches as a parameter changes. We also investigate the backward bifurcation, the Hopf bifurcation and Bogdanov-Takens bifurcation and obtain the Hopf bifurcation criteria and Bogdanov-Takens bifurcation curves, which are important for making strategies for controlling a disease
Bayesian geostatistical modeling of leishmaniasis incidence in Brazil.
Directory of Open Access Journals (Sweden)
Dimitrios-Alexios Karagiannis-Voules
Full Text Available BACKGROUND: Leishmaniasis is endemic in 98 countries with an estimated 350 million people at risk and approximately 2 million cases annually. Brazil is one of the most severely affected countries. METHODOLOGY: We applied Bayesian geostatistical negative binomial models to analyze reported incidence data of cutaneous and visceral leishmaniasis in Brazil covering a 10-year period (2001-2010. Particular emphasis was placed on spatial and temporal patterns. The models were fitted using integrated nested Laplace approximations to perform fast approximate Bayesian inference. Bayesian variable selection was employed to determine the most important climatic, environmental, and socioeconomic predictors of cutaneous and visceral leishmaniasis. PRINCIPAL FINDINGS: For both types of leishmaniasis, precipitation and socioeconomic proxies were identified as important risk factors. The predicted number of cases in 2010 were 30,189 (standard deviation [SD]: 7,676 for cutaneous leishmaniasis and 4,889 (SD: 288 for visceral leishmaniasis. Our risk maps predicted the highest numbers of infected people in the states of Minas Gerais and Pará for visceral and cutaneous leishmaniasis, respectively. CONCLUSIONS/SIGNIFICANCE: Our spatially explicit, high-resolution incidence maps identified priority areas where leishmaniasis control efforts should be targeted with the ultimate goal to reduce disease incidence.
Filaggrin loss-of-function mutations and incident cancer
DEFF Research Database (Denmark)
Skaaby, T; Husemoen, L L N; Thyssen, J P
2014-01-01
BACKGROUND: Loss-of-function mutations in the filaggrin gene (FLG) could have opposing effects on cancer risk, as mutations are associated with both 10% higher serum vitamin D levels, which may protect against cancer, and with impaired skin barrier function, which may lead to higher cancer...... (HR 1·09, 95% CI 0·61-1·94), urinary cancer (HR 1·30, 95% CI 0·51-3·29), malignant melanoma (HR 1·03, 95% CI 0·41-2·58) and NMSC (HR 0·70, 95% CI 0·47-1·05). Among participants aged over 60 years at baseline, we found statistically significant lower risks of all cancers and NMSC among FLG mutation...
International Nuclear Information System (INIS)
Hurkmans, A.; Overbosch, E.G.; Olander, D.R.; Los, J.
1976-01-01
The trapping probability of potassium atoms on a polycrystalline tungsten surface has been measured as a function of the angle of incidence and as a function of the energy of the incoming atoms. Below an energy of 1 eV the trapping was complete; above 20 eV only reflection occurred. The trapping probability increased with increasing angle of incidence. The measurements are compared with a simple model of the fraction of atoms initially trapped. The model, a one-dimensional cube model including a Boltzmann distribution of the velocities of oscillating surface atoms, partially explains the data. The trapping probability as a function of incoming energy is well described for normal incidence, justifying the inclusion of thermal motion of the surface atoms in the model. The angular dependence can be explained in a qualitative way, although there is a substantial discrepancy for large angles of incidence, showing the presence of surface structure. (Auth.)
Yanik, Elizabeth L; Clarke, Christina A; Snyder, Jon J; Pfeiffer, Ruth M; Engels, Eric A
2016-05-01
Among patients with ESRD, cancer risk is affected by kidney dysfunction and by immunosuppression after transplant. Assessing patterns across periods of dialysis and kidney transplantation may inform cancer etiology. We evaluated 202,195 kidney transplant candidates and recipients from a linkage between the Scientific Registry of Transplant Recipients and cancer registries, and compared incidence in kidney function intervals (time with a transplant) with incidence in nonfunction intervals (waitlist or time after transplant failure), adjusting for demographic factors. Incidence of infection-related and immune-related cancer was higher during kidney function intervals than during nonfunction intervals. Incidence was most elevated for Kaposi sarcoma (hazard ratio [HR], 9.1; 95% confidence interval (95% CI), 4.7 to 18), non-Hodgkin's lymphoma (HR, 3.2; 95% CI, 2.8 to 3.7), Hodgkin's lymphoma (HR, 3.0; 95% CI, 1.7 to 5.3), lip cancer (HR, 3.4; 95% CI, 2.0 to 6.0), and nonepithelial skin cancers (HR, 3.8; 95% CI, 2.5 to 5.8). Conversely, ESRD-related cancer incidence was lower during kidney function intervals (kidney cancer: HR, 0.8; 95% CI, 0.7 to 0.8 and thyroid cancer: HR, 0.7; 95% CI, 0.6 to 0.8). With each successive interval, incidence changed in alternating directions for non-Hodgkin's lymphoma, melanoma, and lung, pancreatic, and nonepithelial skin cancers (higher during function intervals), and kidney and thyroid cancers (higher during nonfunction intervals). For many cancers, incidence remained higher than in the general population across all intervals. These data indicate strong short-term effects of kidney dysfunction and immunosuppression on cancer incidence in patients with ESRD, suggesting a need for persistent cancer screening and prevention. Copyright © 2016 by the American Society of Nephrology.
Smooth semi-nonparametric (SNP) estimation of the cumulative incidence function.
Duc, Anh Nguyen; Wolbers, Marcel
2017-08-15
This paper presents a novel approach to estimation of the cumulative incidence function in the presence of competing risks. The underlying statistical model is specified via a mixture factorization of the joint distribution of the event type and the time to the event. The time to event distributions conditional on the event type are modeled using smooth semi-nonparametric densities. One strength of this approach is that it can handle arbitrary censoring and truncation while relying on mild parametric assumptions. A stepwise forward algorithm for model estimation and adaptive selection of smooth semi-nonparametric polynomial degrees is presented, implemented in the statistical software R, evaluated in a sequence of simulation studies, and applied to data from a clinical trial in cryptococcal meningitis. The simulations demonstrate that the proposed method frequently outperforms both parametric and nonparametric alternatives. They also support the use of 'ad hoc' asymptotic inference to derive confidence intervals. An extension to regression modeling is also presented, and its potential and challenges are discussed. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.
Riediger, Natalie D; Clark, Kirsten; Lukianchuk, Virginia; Roulette, Joanne; Bruce, Sharon
2017-01-01
Diabetes prevalence is substantially higher among Canadian First Nations populations than the non-First Nation population. Fasting serum triglycerides have been found to be an important predictor of incident diabetes among non-indigenous populations. However, there is a great need to understand diabetes progression within specific ethnic groups, particularly First Nations populations. The purpose of this study was to test for an association between fasting serum triglycerides and incident diabetes, changes in insulin resistance and changes in β-cell function in a Manitoba First Nation cohort. Study data were from two diabetes screening studies in Sandy Bay First Nation in Manitoba, Canada, collected in 2002/2003 and 2011/2012. The cohort was composed of respondents to both screening studies (n=171). Fasting blood samples and anthropometric, health and demographic data were collected. A generalised linear model with Poisson distribution was used to test for an association between fasting triglycerides and incident diabetes. There were 35 incident cases of diabetes among 128 persons without diabetes at baseline. Participants who developed incident type 2 diabetes were significantly older and had significantly higher body mass index (BMI; p=0.012), total cholesterol (p=0.007), fasting triglycerides (ptriglyceride level was found to be a statistically significant positive predictor of incident diabetes independent of age, sex and waist circumference at baseline. Participants with triglycerides in the highest tertile (≥2.11 mmol/l) had a 4.0-times higher risk of developing incident diabetes compared to those in the lowest tertile (p=0.03). Notably, neither waist circumference nor BMI were significant predictors of incident diabetes independent of age, sex and triglycerides. Fasting triglycerides may be useful as a clinical predictor of insulin resistance and diabetes development among First Nations populations. Unlike other ethnic groups, BMI and waist circumference
Motor function and incident dementia: a systematic review and meta-analysis.
Kueper, Jacqueline Kathleen; Speechley, Mark; Lingum, Navena Rebecca; Montero-Odasso, Manuel
2017-09-01
cognitive and mobility decline are interrelated processes, whereby mobility decline coincides or precedes the onset of cognitive decline. to assess whether there is an association between performance on motor function tests and incident dementia. electronic database, grey literature and hand searching identified studies testing for associations between baseline motor function and incident dementia in older adults. of 2,540 potentially relevant documents, 37 met the final inclusion criteria and were reviewed qualitatively. Three meta-analyses were conducted using data from 10 studies. Three main motor domains-upper limb motor function, parkinsonism and lower limb motor function-emerged as associated with increased risk of incident dementia. Studies including older adults without neurological overt disease found a higher risk of incident dementia associated with poorer performance on composite motor function scores, balance and gait velocity (meta-analysis pooled HR = 1.94, 95% CI: 1.41, 2.65). Mixed results were found across different study samples for upper limb motor function, overall parkinsonism (meta-analysis pooled OR = 3.05, 95% CI: 1.31, 7.08), bradykinesia and rigidity. Studies restricted to older adults with Parkinson's Disease found weak or no association with incident dementia even for motor domains highly associated in less restrictive samples. Tremor was not associated with an increased risk of dementia in any population (meta-analysis pooled HR = 0.80, 95% CI 0.31, 2.03). lower limb motor function was associated with increased risk of developing dementia, while tremor and hand grip strength were not. Our results support future research investigating the inclusion of quantitative motor assessment, specifically gait velocity tests, for clinical dementia risk evaluation. © The Author 2017. Published by Oxford University Press on behalf of the British Geriatrics Society.All rights reserved. For permissions, please email: journals.permissions@oup.com
Bancks, Michael P; Alonso, Alvaro; Gottesman, Rebecca F; Mosley, Thomas H; Selvin, Elizabeth; Pankow, James S
2017-12-01
Diabetes is prospectively associated with cognitive decline. Whether lower cognitive function and worse brain structure are prospectively associated with incident diabetes is unclear. We analyzed data for 10,133 individuals with cognitive function testing (1990-1992) and 1212 individuals with brain magnetic resonance imaging (1993-1994) from the Atherosclerosis Risk in Communities cohort. We estimated hazard ratios for incident diabetes through 2014 after adjustment for traditional diabetes risk factors and cohort attrition. Higher level of baseline cognitive function was associated with lower risk for diabetes (per 1 standard deviation, hazard ratio = 0.94; 95% confidence interval = 0.90, 0.98). This association did not persist after accounting for baseline glucose level, case ascertainment methods, and cohort attrition. No association was observed between any brain magnetic resonance imaging measure and incident diabetes. This is one of the first studies to prospectively evaluate the association between both cognitive function and brain structure and the incidence of diabetes. Copyright © 2017 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.
DEFF Research Database (Denmark)
Effraimidis, Georgios; Dahl, Christian Møller
In this paper, we develop a fully nonparametric approach for the estimation of the cumulative incidence function with Missing At Random right-censored competing risks data. We obtain results on the pointwise asymptotic normality as well as the uniform convergence rate of the proposed nonparametric...
Spatio-temporal modelling of dengue fever incidence in Malaysia
Che-Him, Norziha; Ghazali Kamardan, M.; Saifullah Rusiman, Mohd; Sufahani, Suliadi; Mohamad, Mahathir; @ Kamariah Kamaruddin, Nafisah
2018-04-01
Previous studies reported significant relationship between dengue incidence rate (DIR) and both climatic and non-climatic factors. Therefore, this study proposes a generalised additive model (GAM) framework for dengue risk in Malaysia by using both climatic and non-climatic factors. The data used is monthly DIR for 12 states of Malaysia from 2001 to 2009. In this study, we considered an annual trend, seasonal effects, population, population density and lagged DIR, rainfall, temperature, number of rainy days and El Niño-Southern Oscillation (ENSO). The population density is found to be positively related to monthly DIR. There are generally weak relationships between monthly DIR and climate variables. A negative binomial GAM shows that there are statistically significant relationships between DIR with climatic and non-climatic factors. These include mean rainfall and temperature, the number of rainy days, sea surface temperature and the interaction between mean temperature (lag 1 month) and sea surface temperature (lag 6 months). These also apply to DIR (lag 3 months) and population density.
Taveira-DaSilva, Angelo M; Julien-Williams, Patricia; Jones, Amanda M; Moss, Joel
2016-07-01
Because pneumothorax is frequent in lymphangioleiomyomatosis, patients have expressed concerns regarding the risk of pneumothorax associated with pulmonary function or exercise testing. Indeed, pneumothorax has been reported in patients with lung disease after both of these tests. The aim of this study was to determine the incidence of pneumothorax in patients with lymphangioleiomyomatosis during admissions to the National Institutes of Health Clinical Research Center between 1995 and 2015. Medical records were reviewed to identify patients who had a pneumothorax during their stay at the National Institutes of Health. A total of 691 patients underwent 4,523 pulmonary function tests and 1,900 exercise tests. Three patients developed pneumothorax after pulmonary function tests and/or exercise tests. The incidence of pneumothorax associated with lung function testing was 0.14 to 0.29 of 100 patients or 0.02 to 0.04 of 100 tests. The incidence of pneumothorax in patients undergoing exercise testing was 0.14 to 0.28 of 100 patients or 0.05 to 0.10 of 100 tests. The risk of pneumothorax associated with pulmonary function or exercise testing in patients with lymphangioleiomyomatosis is low. Published by Elsevier Inc.
Sahle, Berhe W; Owen, Alice J; Chin, Ken Lee; Reid, Christopher M
2017-09-01
Numerous models predicting the risk of incident heart failure (HF) have been developed; however, evidence of their methodological rigor and reporting remains unclear. This study critically appraises the methods underpinning incident HF risk prediction models. EMBASE and PubMed were searched for articles published between 1990 and June 2016 that reported at least 1 multivariable model for prediction of HF. Model development information, including study design, variable coding, missing data, and predictor selection, was extracted. Nineteen studies reporting 40 risk prediction models were included. Existing models have acceptable discriminative ability (C-statistics > 0.70), although only 6 models were externally validated. Candidate variable selection was based on statistical significance from a univariate screening in 11 models, whereas it was unclear in 12 models. Continuous predictors were retained in 16 models, whereas it was unclear how continuous variables were handled in 16 models. Missing values were excluded in 19 of 23 models that reported missing data, and the number of events per variable was models. Only 2 models presented recommended regression equations. There was significant heterogeneity in discriminative ability of models with respect to age (P prediction models that had sufficient discriminative ability, although few are externally validated. Methods not recommended for the conduct and reporting of risk prediction modeling were frequently used, and resulting algorithms should be applied with caution. Copyright © 2017 Elsevier Inc. All rights reserved.
Qualitative analysis of nonlinear incidence rate upon the behaviour of an epidemiological model
International Nuclear Information System (INIS)
Li Xiaogui.
1988-12-01
Two theorems concerning the solutions of the system of differential equations describing an epidemiological model with nonlinear incidence rate per infective individual are demonstrated. 2 refs, 1 fig
Loha, Eskindir; Lindtjørn, Bernt
2010-06-16
Malaria transmission is complex and is believed to be associated with local climate changes. However, simple attempts to extrapolate malaria incidence rates from averaged regional meteorological conditions have proven unsuccessful. Therefore, the objective of this study was to determine if variations in specific meteorological factors are able to consistently predict P. falciparum malaria incidence at different locations in south Ethiopia. Retrospective data from 42 locations were collected including P. falciparum malaria incidence for the period of 1998-2007 and meteorological variables such as monthly rainfall (all locations), temperature (17 locations), and relative humidity (three locations). Thirty-five data sets qualified for the analysis. Ljung-Box Q statistics was used for model diagnosis, and R squared or stationary R squared was taken as goodness of fit measure. Time series modelling was carried out using Transfer Function (TF) models and univariate auto-regressive integrated moving average (ARIMA) when there was no significant predictor meteorological variable. Of 35 models, five were discarded because of the significant value of Ljung-Box Q statistics. Past P. falciparum malaria incidence alone (17 locations) or when coupled with meteorological variables (four locations) was able to predict P. falciparum malaria incidence within statistical significance. All seasonal AIRMA orders were from locations at altitudes above 1742 m. Monthly rainfall, minimum and maximum temperature was able to predict incidence at four, five and two locations, respectively. In contrast, relative humidity was not able to predict P. falciparum malaria incidence. The R squared values for the models ranged from 16% to 97%, with the exception of one model which had a negative value. Models with seasonal ARIMA orders were found to perform better. However, the models for predicting P. falciparum malaria incidence varied from location to location, and among lagged effects, data
Directory of Open Access Journals (Sweden)
Loha Eskindir
2010-06-01
Full Text Available Abstract Background Malaria transmission is complex and is believed to be associated with local climate changes. However, simple attempts to extrapolate malaria incidence rates from averaged regional meteorological conditions have proven unsuccessful. Therefore, the objective of this study was to determine if variations in specific meteorological factors are able to consistently predict P. falciparum malaria incidence at different locations in south Ethiopia. Methods Retrospective data from 42 locations were collected including P. falciparum malaria incidence for the period of 1998-2007 and meteorological variables such as monthly rainfall (all locations, temperature (17 locations, and relative humidity (three locations. Thirty-five data sets qualified for the analysis. Ljung-Box Q statistics was used for model diagnosis, and R squared or stationary R squared was taken as goodness of fit measure. Time series modelling was carried out using Transfer Function (TF models and univariate auto-regressive integrated moving average (ARIMA when there was no significant predictor meteorological variable. Results Of 35 models, five were discarded because of the significant value of Ljung-Box Q statistics. Past P. falciparum malaria incidence alone (17 locations or when coupled with meteorological variables (four locations was able to predict P. falciparum malaria incidence within statistical significance. All seasonal AIRMA orders were from locations at altitudes above 1742 m. Monthly rainfall, minimum and maximum temperature was able to predict incidence at four, five and two locations, respectively. In contrast, relative humidity was not able to predict P. falciparum malaria incidence. The R squared values for the models ranged from 16% to 97%, with the exception of one model which had a negative value. Models with seasonal ARIMA orders were found to perform better. However, the models for predicting P. falciparum malaria incidence varied from location
Traffic Incident Clearance Time and Arrival Time Prediction Based on Hazard Models
Directory of Open Access Journals (Sweden)
Yang beibei Ji
2014-01-01
Full Text Available Accurate prediction of incident duration is not only important information of Traffic Incident Management System, but also an effective input for travel time prediction. In this paper, the hazard based prediction models are developed for both incident clearance time and arrival time. The data are obtained from the Queensland Department of Transport and Main Roads’ STREAMS Incident Management System (SIMS for one year ending in November 2010. The best fitting distributions are drawn for both clearance and arrival time for 3 types of incident: crash, stationary vehicle, and hazard. The results show that Gamma, Log-logistic, and Weibull are the best fit for crash, stationary vehicle, and hazard incident, respectively. The obvious impact factors are given for crash clearance time and arrival time. The quantitative influences for crash and hazard incident are presented for both clearance and arrival. The model accuracy is analyzed at the end.
Ferree, Steven; van der Vliet, Quirine M J; van Heijl, Mark; Houwert, Roderick M; Leenen, Luke P H; Hietbrink, Falco
2017-04-01
Injuries of the hand can cause significant functional impairment, diminished quality of life and delayed return to work. However, the incidence and functional outcome of hand injuries in polytrauma patients is currently unknown. The aim of this study was to determine the incidence, distribution and functional outcome of fractures and dislocation of the hand in polytrauma patients. A single centre retrospective cohort study was performed at a level 1 trauma centre. Polytrauma was defined as patients with an Injury Severity Score of 16 or higher. Fractures and dislocations to the hand were determined. All eligible polytrauma patients with hand injuries were included and a Quick Disability of Arm, Shoulder and Hand questionnaire (QDASH) and Patient-Rated Wrist/Hand Evaluation (PRWHE) were administered. Patients were contacted 1-6 years after trauma. In a cohort of 2046 polytrauma patients 72 patients (3.5%) suffered a hand injury. The functional outcome scores of 52 patients (72%) were obtained. The Metacarpal (48%) and carpal (33%) bones were the most frequently affected. The median QDASH score for all patients with hand injury was 17 (IQR 0-31) and the PRWHE 14 (IQR 0-41). Patients with a concomitant upper extremity injury (p=0.002 for PRWHE, p0.006 for QDASH) and those with higher ISS scores (p=0.034 for PRWHE, QDASH not significant) had worse functional outcome scores. As an example, of the 5 patients with the worst outcome scores 3 suffered an isolated phalangeal injury, all had concomitant upper extremity injury or neurological injuries (3 plexus injuries, 1 severe brain injury). The incidence of hand injuries in polytrauma patients is 3.5%, which is relatively low compared to a general trauma population. Metacarpal and carpal bones were most frequently affected. The functional extremity specific outcome scores are highly influenced by concomitant injuries (upper extremity injuries, neurological injuries and higher ISS). Copyright © 2017 Elsevier Ltd. All
Directory of Open Access Journals (Sweden)
Chelsea Uggenti
2018-03-01
Full Text Available We begin with a detailed study of a delayed SI model of disease transmission with immigration into both classes. The incidence function allows for a nonlinear dependence on the infected population, including mass action and saturating incidence as special cases. Due to the immigration of infectives, there is no disease-free equilibrium and hence no basic reproduction number. We show there is a unique endemic equilibrium and that this equilibrium is globally asymptotically stable for all parameter values. The results include vector-style delay and latency-style delay. Next, we show that previous global stability results for an SEI model and an SVI model that include immigration of infectives and non-linear incidence but not delay can be extended to systems with vector-style delay and latency-style delay.
PREDICTIVE MODELS FOR SUPPORT OF INCIDENT MANAGEMENT PROCESS IN IT SERVICE MANAGEMENT
Directory of Open Access Journals (Sweden)
Martin SARNOVSKY
2018-03-01
Full Text Available ABSTRACT The work presented in this paper is focused on creating of predictive models that help in the process of incident resolution and implementation of IT infrastructure changes to increase the overall support of IT management. Our main objective was to build the predictive models using machine learning algorithms and CRISP-DM methodology. We used the incident and related changes database obtained from the IT environment of the Rabobank Group company, which contained information about the processing of the incidents during the incident management process. We decided to investigate the dependencies between the incident observation on particular infrastructure component and the actual source of the incident as well as the dependency between the incidents and related changes in the infrastructure. We used Random Forests and Gradient Boosting Machine classifiers in the process of identification of incident source as well as in the prediction of possible impact of the observed incident. Both types of models were tested on testing set and evaluated using defined metrics.
Statistical modelling with quantile functions
Gilchrist, Warren
2000-01-01
Galton used quantiles more than a hundred years ago in describing data. Tukey and Parzen used them in the 60s and 70s in describing populations. Since then, the authors of many papers, both theoretical and practical, have used various aspects of quantiles in their work. Until now, however, no one put all the ideas together to form what turns out to be a general approach to statistics.Statistical Modelling with Quantile Functions does just that. It systematically examines the entire process of statistical modelling, starting with using the quantile function to define continuous distributions. The author shows that by using this approach, it becomes possible to develop complex distributional models from simple components. A modelling kit can be developed that applies to the whole model - deterministic and stochastic components - and this kit operates by adding, multiplying, and transforming distributions rather than data.Statistical Modelling with Quantile Functions adds a new dimension to the practice of stati...
Executive function, but not memory, associates with incident coronary heart disease and stroke
DEFF Research Database (Denmark)
Rostamian, Somayeh; van Buchem, Mark A; Westendorp, Rudi G J
2015-01-01
OBJECTIVE: To evaluate the association of performance in cognitive domains executive function and memory with incident coronary heart disease and stroke in older participants without dementia. METHODS: We included 3,926 participants (mean age 75 years, 44% male) at risk for cardiovascular diseases...... from the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) with Mini-Mental State Examination score ≥24 points. Scores on the Stroop Color-Word Test (selective attention) and the Letter Digit Substitution Test (processing speed) were converted to Z scores and averaged into a composite...... executive function score. Likewise, scores of the Picture Learning Test (immediate and delayed memory) were transformed into a composite memory score. Associations of executive function and memory were longitudinally assessed with risk of coronary heart disease and stroke using multivariable Cox regression...
Effect of climate variables on cocoa black pod incidence in Sabah using ARIMAX model
Ling Sheng Chang, Albert; Ramba, Haya; Mohd. Jaaffar, Ahmad Kamil; Kim Phin, Chong; Chong Mun, Ho
2016-06-01
Cocoa black pod disease is one of the major diseases affecting the cocoa production in Malaysia and also around the world. Studies have shown that the climate variables have influenced the cocoa black pod disease incidence and it is important to quantify the black pod disease variation due to the effect of climate variables. Application of time series analysis especially auto-regressive moving average (ARIMA) model has been widely used in economics study and can be used to quantify the effect of climate variables on black pod incidence to forecast the right time to control the incidence. However, ARIMA model does not capture some turning points in cocoa black pod incidence. In order to improve forecasting performance, other explanatory variables such as climate variables should be included into ARIMA model as ARIMAX model. Therefore, this paper is to study the effect of climate variables on the cocoa black pod disease incidence using ARIMAX model. The findings of the study showed ARIMAX model using MA(1) and relative humidity at lag 7 days, RHt - 7 gave better R square value compared to ARIMA model using MA(1) which could be used to forecast the black pod incidence to assist the farmers determine timely application of fungicide spraying and culture practices to control the black pod incidence.
Porter, Chad K; Gormley, Robert; Tribble, David R; Cash, Brooks D; Riddle, Mark S
2011-01-01
Functional gastrointestinal disorders (FGDs) are recognized sequelae of infectious gastroenteritis (IGE). Within the active duty military population, a group with known high IGE rates, the population-based incidence, risk factors, and attributable burden of care referable to FGD after IGE are poorly defined. Using electronic medical encounter data (1999-2007) on active duty US military, a matched, case-control study describing the epidemiology and risk determinants of FGD (irritable bowel syndrome (IBS), functional constipation (FC), functional diarrhea (FD), dyspepsia (D)) was conducted. Incidence rates and duration of FGD-related medical care were estimated, and conditional logistic regression was utilized to evaluate FGD risk after IGE. A total of 31,866 cases of FGD identified were distributed as follows: FC 55% (n=17,538), D 21.2% (n=6,750), FD 2.1% (n=674), IBS 28.5% (n=9,091). Previous IGE episodes were distributed as follows: specific bacterial pathogen (n=65, 1.2%), bacterial, with no pathogen specified (n=2155, 38.9%), protozoal (n=38, 0.7%), viral (n=3431, 61.9%). A significant association between IGE and all FGD (odds ratio (OR) 2.64; Phigh risk for IGE. When considering effective countermeasures and mitigation strategies, attention directed toward prevention as well as the acute and chronic sequelae of these infections is needed.
Camargo, L F; Esteves, A B A; Ulisses, L R S; Rivelli, G G; Mazzali, M
2014-01-01
Urinary tract infection (UTI) is the most common infection posttransplant. However, the risk factors for and the impact of UTIs remain controversial. The aim of this study was to identify the incidence of posttransplant UTIs in a series of renal transplant recipients from deceased donors. Secondary objectives were to identify: (1) the most frequent infectious agents; (2) risk factors related to donor; (3) risk factors related to recipients; and (4) impact of UTI on graft function. This was a retrospective analysis of medical records from renal transplant patients from January to December 2010. Local ethics committee approved the protocol. The incidence of UTI in this series was 34.2%. Risk factors for UTI were older age, (independent of gender), biopsy-proven acute rejection episodes, and kidneys from deceased donors (United Network for Organ Sharing criteria). For female patients, the number of pretransplant pregnancies was an additional risk factor. Recurrent UTI was observed in 44% of patients from the UTI group. The most common infectious agents were Escherichia coli and Klebsiella pneumoniae, for both isolated and recurrent UTI. No difference in renal graft function or immunosuppressive therapy was observed between groups after the 1-year follow-up. In this series, older age, previous pregnancy, kidneys from expanded criteria donors, and biopsy-proven acute rejection episodes were risk factors for posttransplant UTI. Recurrence of UTI was observed in 44%, with no negative impact on graft function or survival. Copyright © 2014 Elsevier Inc. All rights reserved.
Functioning with a Sticky Model.
Reys, Robert E.
1981-01-01
A model that can be effectively used to develop the notion of function and provide varied practice by using "real world" examples and concrete objects is covered. The use of Popsicle-sticks is featured, with some suggestions for tasks involving functions with one operation, two operations, and inverse operations covered. (MP)
75 FR 80735 - Special Conditions: Gulfstream Model GVI Airplane; High Incidence Protection
2010-12-23
... Special Conditions No. 25-10-03-SC] Special Conditions: Gulfstream Model GVI Airplane; High Incidence... airworthiness standards for transport category airplanes associated with the use of high incidence protection... transport airplane with an executive cabin interior. The maximum takeoff weight will be 99,600 pounds, with...
76 FR 17022 - Special Conditions: Gulfstream Model GVI Airplane; High Incidence Protection
2011-03-28
... Special Conditions No. 25-423-SC] Special Conditions: Gulfstream Model GVI Airplane; High Incidence... for transport category airplanes associated with the use of high incidence protection. The applicable... with an executive cabin interior. The maximum takeoff weight will be 99,600 pounds, with a maximum...
77 FR 32006 - Special Conditions: Gulfstream Model GVI Airplane; High Incidence Protection
2012-05-31
... Special Conditions No. 25-423-SC] Special Conditions: Gulfstream Model GVI Airplane; High Incidence... pertaining to a high incidence protection system that replaces the stall warning system during normal... the condition existing in the test or performance standard in which V SR is being used. (3) The weight...
A deterministic width function model
Directory of Open Access Journals (Sweden)
C. E. Puente
2003-01-01
Full Text Available Use of a deterministic fractal-multifractal (FM geometric method to model width functions of natural river networks, as derived distributions of simple multifractal measures via fractal interpolating functions, is reported. It is first demonstrated that the FM procedure may be used to simulate natural width functions, preserving their most relevant features like their overall shape and texture and their observed power-law scaling on their power spectra. It is then shown, via two natural river networks (Racoon and Brushy creeks in the United States, that the FM approach may also be used to closely approximate existing width functions.
Study on the incidence and etiology of subclinical thyroid function disorders
International Nuclear Information System (INIS)
Gu Jingxin; Xie Xiuhai; Huang Chenyang; Fu Junyan; Lu Weiguo; Chen Kejing
2006-01-01
Objective: To study the incidence and etiology of subclinical thyroid function disorders in 12592 subjects tested. Methods: The etiology of 874 patients with abnormal serum TSH (with IRMA) found in the tested 12592 patients, whose serum T 3 , T 4 , FT 3 , FT 4 , TSH, TGA and TMA were also detected with RIA was analyzed. Results: 874 of 12592 patients had abnormal TSH levels (6.94%). Among them, TSH was elevated in 397 patients (3.15%) and decreased in 477 patients (3.79%). Most of them were associated with obvious related thyroid or other thronic diseases such as hyperthyroidism after therapy, thyroxine replacement treatment of hypothyroidism and other thyroid diseases (thyroiditis, diffuse nontoxic goiter). In the remaining apparently disease-free 143 subjects, there were with subclinical hypothyroidism and 34 (3.89% of 874) with subclinical hyperthyroidism. Also among the 874 patients, 30.78% (n=269) patients had elevated TGA and TMA[16.82% (n=147) had elevated TSH and TGA, TMA simultaneously, 13.96% (n=122) had decreased TSH and elevated TGA and TMA simultaneously]. In the 874 patients, 256 (29.29%) were older than 60. Conclusion: Elderly people has higher incidence of subclinical thyroid function disorders. We should pay more attention to the detection of this condition, especially in elderly patients. (authors)
The Incidence of Sixteenth Century Cosmic Models in Modern Texts
Maene, S. A.; Best, J. S.; Usher, P. D.
1999-12-01
In the sixteenth century, the bounded cosmological models of Copernicus (1543) and Tycho Brahe (1588), and the unbounded model of Thomas Digges (1576), vied with the bounded geocentric model of Ptolemy (c. 140 AD). The work of the philosopher Giordano Bruno in 1584 lent further support to the Digges model. Despite the eventual acceptance of the unbounded universe, analysis of over 100 modern introductory astronomy texts reveals that these early unbounded models are mentioned infrequently. The ratio of mentions of Digges' model to Copernicus' model has the surprisingly low value of R = 0.08. The philosophical speculation of Bruno receives mention more than twice as often (R = 0.17). The expectation that these early unbounded models warrant inclusion in astronomy texts is supported both by modern hindsight and by the literature of the time. In Shakespeare's "Hamlet" of c. 1601, Prince Hamlet suffers from two transformations. According to the cosmic allegorical model, one transformation changes the bounded geocentricism of Ptolemy to the bounded heliocentricism of Copernicus, while the other completes the change to Digges' model of the infinite universe of suns. This interpretation and the modern world view suggest that both transformations should receive equal mention and thus that the ratio R in introductory texts should be close to unity. This work was supported in part by the NASA West Virginia Space Grant Consortium.
Incidence of loss of ability to walk 400 meters in a functionally limited older population.
Chang, Milan; Cohen-Mansfield, Jiska; Ferrucci, Luigi; Leveille, Suzanne; Volpato, Stefano; de Rekeneire, Nathalie; Guralnik, Jack M
2004-12-01
To assess the incidence of and factors related to nondisabled but functionally limited older adults aged 75 to 85 years losing the ability to walk 400 m. Observational study with average follow-up of 21 months. Community. At baseline, 101 persons with objective signs of functional limitations and intact cognitive function agreed to participate in the study. Of these, 81 were able to walk 400 m at baseline, and 62 participated in the follow-up examination. Mobility disability was defined as an inability to complete a 400-m walk test. At baseline, eligible participants (n=81) had the ability to walk 400 m, scored between 4 and 9 on the Short Physical Performance Battery (SPPB; range 0-12), and scored 18 or more on the Mini-Mental State Examination. Demographics, difficulty in daily activities, disease status, behavioral risk factors, and muscle strength were assessed at baseline and follow-up. Of 62 persons at follow-up, 21 (33.9%) developed incident mobility disability. The strongest predictors of loss of mobility were the time to complete the 400-m walk at baseline (odds ratio (OR)=1.6 per 1-minute difference, 95% confidence interval (CI)=1.04-2.45), and decline in SPPB score over the follow-up (OR=1.4 per 1-point difference, 95% CI=1.01-1.92). Older persons with functional limitations have a high rate of loss of ability to walk 400 m. The 400-m walk test is a highly relevant, discrete outcome that is an ideal target for testing preventive interventions in vulnerable older populations.
Development of a subway operation incident delay model using accelerated failure time approaches.
Weng, Jinxian; Zheng, Yang; Yan, Xuedong; Meng, Qiang
2014-12-01
This study aims to develop a subway operational incident delay model using the parametric accelerated time failure (AFT) approach. Six parametric AFT models including the log-logistic, lognormal and Weibull models, with fixed and random parameters are built based on the Hong Kong subway operation incident data from 2005 to 2012, respectively. In addition, the Weibull model with gamma heterogeneity is also considered to compare the model performance. The goodness-of-fit test results show that the log-logistic AFT model with random parameters is most suitable for estimating the subway incident delay. First, the results show that a longer subway operation incident delay is highly correlated with the following factors: power cable failure, signal cable failure, turnout communication disruption and crashes involving a casualty. Vehicle failure makes the least impact on the increment of subway operation incident delay. According to these results, several possible measures, such as the use of short-distance and wireless communication technology (e.g., Wifi and Zigbee) are suggested to shorten the delay caused by subway operation incidents. Finally, the temporal transferability test results show that the developed log-logistic AFT model with random parameters is stable over time. Copyright © 2014 Elsevier Ltd. All rights reserved.
Xu, Meng; Xue, Wanli; Ma, Zhenhua; Bai, Jigang
2016-01-01
Purpose. To investigate the preventive effect of resveratrol (RES) on the formation of portal vein system thrombosis (PVST) in a rat fibrosis model. Methods. A total of 64 male SD rats, weighing 200–300 g, were divided into five groups: Sham operation, Splenectomy I, Splenectomy II, RES, and low molecular weight heparin (LMWH), with the former two groups as nonfibrosis controls. Blood samples were subjected to biochemical assays. Platelet apoptosis was measured by flow cytometry. All rats were euthanized for PVST detection one week after operation. Results. No PVST occurred in nonfibrosis controls. Compared to Splenectomy II, the incidences of PVST in RES and LMWH groups were significantly decreased (both p Splenectomy II (all p splenectomy in cirrhotic rat. Regulation of platelet function and induction of platelet apoptosis might be the underlying mechanisms. PMID:27433290
Time Series Modelling of Syphilis Incidence in China from 2005 to 2012.
Zhang, Xingyu; Zhang, Tao; Pei, Jiao; Liu, Yuanyuan; Li, Xiaosong; Medrano-Gracia, Pau
2016-01-01
The infection rate of syphilis in China has increased dramatically in recent decades, becoming a serious public health concern. Early prediction of syphilis is therefore of great importance for heath planning and management. In this paper, we analyzed surveillance time series data for primary, secondary, tertiary, congenital and latent syphilis in mainland China from 2005 to 2012. Seasonality and long-term trend were explored with decomposition methods. Autoregressive integrated moving average (ARIMA) was used to fit a univariate time series model of syphilis incidence. A separate multi-variable time series for each syphilis type was also tested using an autoregressive integrated moving average model with exogenous variables (ARIMAX). The syphilis incidence rates have increased three-fold from 2005 to 2012. All syphilis time series showed strong seasonality and increasing long-term trend. Both ARIMA and ARIMAX models fitted and estimated syphilis incidence well. All univariate time series showed highest goodness-of-fit results with the ARIMA(0,0,1)×(0,1,1) model. Time series analysis was an effective tool for modelling the historical and future incidence of syphilis in China. The ARIMAX model showed superior performance than the ARIMA model for the modelling of syphilis incidence. Time series correlations existed between the models for primary, secondary, tertiary, congenital and latent syphilis.
Time Series Modelling of Syphilis Incidence in China from 2005 to 2012
Zhang, Xingyu; Zhang, Tao; Pei, Jiao; Liu, Yuanyuan; Li, Xiaosong; Medrano-Gracia, Pau
2016-01-01
Background The infection rate of syphilis in China has increased dramatically in recent decades, becoming a serious public health concern. Early prediction of syphilis is therefore of great importance for heath planning and management. Methods In this paper, we analyzed surveillance time series data for primary, secondary, tertiary, congenital and latent syphilis in mainland China from 2005 to 2012. Seasonality and long-term trend were explored with decomposition methods. Autoregressive integrated moving average (ARIMA) was used to fit a univariate time series model of syphilis incidence. A separate multi-variable time series for each syphilis type was also tested using an autoregressive integrated moving average model with exogenous variables (ARIMAX). Results The syphilis incidence rates have increased three-fold from 2005 to 2012. All syphilis time series showed strong seasonality and increasing long-term trend. Both ARIMA and ARIMAX models fitted and estimated syphilis incidence well. All univariate time series showed highest goodness-of-fit results with the ARIMA(0,0,1)×(0,1,1) model. Conclusion Time series analysis was an effective tool for modelling the historical and future incidence of syphilis in China. The ARIMAX model showed superior performance than the ARIMA model for the modelling of syphilis incidence. Time series correlations existed between the models for primary, secondary, tertiary, congenital and latent syphilis. PMID:26901682
A joint model of cancer incidence, metastasis, and mortality.
Tran, Qui; Kidwell, Kelley M; Tsodikov, Alex
2017-09-04
Many diseases, especially cancer, are not static, but rather can be summarized by a series of events or stages (e.g. diagnosis, remission, recurrence, metastasis, death). Most available methods to analyze multi-stage data ignore intermediate events and focus on the terminal event or consider (time to) multiple events as independent. Competing-risk or semi-competing-risk models are often deficient in describing the complex relationship between disease progression events which are driven by a shared progression stochastic process. A multi-stage model can only examine two stages at a time and thus fails to capture the effect of one stage on the time spent between other stages. Moreover, most models do not account for latent stages. We propose a semi-parametric joint model of diagnosis, latent metastasis, and cancer death and use nonparametric maximum likelihood to estimate covariate effects on the risks of intermediate events and death and the dependence between them. We illustrate the model with Monte Carlo simulations and analysis of real data on prostate cancer from the SEER database.
Zhang, Shou-ping; Xin, Xiao-kang
2017-07-01
Identification of pollutant sources for river pollution incidents is an important and difficult task in the emergency rescue, and an intelligent optimization method can effectively compensate for the weakness of traditional methods. An intelligent model for pollutant source identification has been established using the basic genetic algorithm (BGA) as an optimization search tool and applying an analytic solution formula of one-dimensional unsteady water quality equation to construct the objective function. Experimental tests show that the identification model is effective and efficient: the model can accurately figure out the pollutant amounts or positions no matter single pollution source or multiple sources. Especially when the population size of BGA is set as 10, the computing results are sound agree with analytic results for a single source amount and position identification, the relative errors are no more than 5 %. For cases of multi-point sources and multi-variable, there are some errors in computing results for the reasons that there exist many possible combinations of the pollution sources. But, with the help of previous experience to narrow the search scope, the relative errors of the identification results are less than 5 %, which proves the established source identification model can be used to direct emergency responses.
Zhang functions and various models
Zhang, Yunong
2015-01-01
This book focuses on solving different types of time-varying problems. It presents various Zhang dynamics (ZD) models by defining various Zhang functions (ZFs) in real and complex domains. It then provides theoretical analyses of such ZD models and illustrates their results. It also uses simulations to substantiate their efficacy and show the feasibility of the presented ZD approach (i.e., different ZFs leading to different ZD models), which is further applied to the repetitive motion planning (RMP) of redundant robots, showing its application potential.
An Incidence Loss Model for Wave Rotors with Axially Aligned Passages
Paxson, Daniel E.
1998-01-01
A simple mathematical model is described to account for the losses incurred when the flow in the duct (port) of a wave rotor is not aligned with the passages. The model, specifically for wave rotors with axially aligned passages, describes a loss mechanism which is sensitive to incident flow angle and Mach number. Implementation of the model in a one-dimensional CFD based wave rotor simulation is presented. Comparisons with limited experimental results are consistent with the model. Sensitivity studies are presented which highlight the significance of the incidence loss relative to other loss mechanisms in the wave rotor.
Modeling patient safety incidents knowledge with the Categorial Structure method.
Souvignet, Julien; Bousquet, Cédric; Lewalle, Pierre; Trombert-Paviot, Béatrice; Rodrigues, Jean Marie
2011-01-01
Following the WHO initiative named World Alliance for Patient Safety (PS) launched in 2004 a conceptual framework developed by PS national reporting experts has summarized the knowledge available. As a second step, the Department of Public Health of the University of Saint Etienne team elaborated a Categorial Structure (a semi formal structure not related to an upper level ontology) identifying the elements of the semantic structure underpinning the broad concepts contained in the framework for patient safety. This knowledge engineering method has been developed to enable modeling patient safety information as a prerequisite for subsequent full ontology development. The present article describes the semantic dissection of the concepts, the elicitation of the ontology requirements and the domain constraints of the conceptual framework. This ontology includes 134 concepts and 25 distinct relations and will serve as basis for an Information Model for Patient Safety.
Settlement Relocation Modeling: Reacting to Merapi’s Eruption Incident
Pramitasari, A.; Buchori, I.
2018-02-01
Merapi eruption has made severe damages in Central Java Province. Klaten was one of the most affected area, specifically in Balerante Village. This research is made to comprehend GIS model on finding alternative locations for impacted settlement in hazardous zones of eruption. The principal objective of the research study is to identify and analyze physical condition, community characteristics, and local government regulation related to settlements relocation plan for impacted area of eruption. The output is location map which classified into four categories, i.e. not available, available with low accessibility, available with medium accessibility, and available with high accessibility.
Alegana, Victor A; Wright, Jim A; Nahzat, Sami M; Butt, Waqar; Sediqi, Amad W; Habib, Naeem; Snow, Robert W; Atkinson, Peter M; Noor, Abdisalan M
2014-01-01
Identifying areas that support high malaria risks and where populations lack access to health care is central to reducing the burden in Afghanistan. This study investigated the incidence of Plasmodium vivax and Plasmodium falciparum using routine data to help focus malaria interventions. To estimate incidence, the study modelled utilisation of the public health sector using fever treatment data from the 2012 national Malaria Indicator Survey. A probabilistic measure of attendance was applied to population density metrics to define the proportion of the population within catchment of a public health facility. Malaria data were used in a Bayesian spatio-temporal conditional-autoregressive model with ecological or environmental covariates, to examine the spatial and temporal variation of incidence. From the analysis of healthcare utilisation, over 80% of the population was within 2 hours' travel of the nearest public health facility, while 64.4% were within 30 minutes' travel. The mean incidence of P. vivax in 2009 was 5.4 (95% Crl 3.2-9.2) cases per 1000 population compared to 1.2 (95% Crl 0.4-2.9) cases per 1000 population for P. falciparum. P. vivax peaked in August while P. falciparum peaked in November. 32% of the estimated 30.5 million people lived in regions where annual incidence was at least 1 case per 1,000 population of P. vivax; 23.7% of the population lived in areas where annual P. falciparum case incidence was at least 1 per 1000. This study showed how routine data can be combined with household survey data to model malaria incidence. The incidence of both P. vivax and P. falciparum in Afghanistan remain low but the co-distribution of both parasites and the lag in their peak season provides challenges to malaria control in Afghanistan. Future improved case definition to determine levels of imported risks may be useful for the elimination ambitions in Afghanistan.
Alegana, Victor A.; Wright, Jim A.; Nahzat, Sami M.; Butt, Waqar; Sediqi, Amad W.; Habib, Naeem; Snow, Robert W.; Atkinson, Peter M.; Noor, Abdisalan M.
2014-01-01
Background Identifying areas that support high malaria risks and where populations lack access to health care is central to reducing the burden in Afghanistan. This study investigated the incidence of Plasmodium vivax and Plasmodium falciparum using routine data to help focus malaria interventions. Methods To estimate incidence, the study modelled utilisation of the public health sector using fever treatment data from the 2012 national Malaria Indicator Survey. A probabilistic measure of attendance was applied to population density metrics to define the proportion of the population within catchment of a public health facility. Malaria data were used in a Bayesian spatio-temporal conditional-autoregressive model with ecological or environmental covariates, to examine the spatial and temporal variation of incidence. Findings From the analysis of healthcare utilisation, over 80% of the population was within 2 hours’ travel of the nearest public health facility, while 64.4% were within 30 minutes’ travel. The mean incidence of P. vivax in 2009 was 5.4 (95% Crl 3.2–9.2) cases per 1000 population compared to 1.2 (95% Crl 0.4–2.9) cases per 1000 population for P. falciparum. P. vivax peaked in August while P. falciparum peaked in November. 32% of the estimated 30.5 million people lived in regions where annual incidence was at least 1 case per 1,000 population of P. vivax; 23.7% of the population lived in areas where annual P. falciparum case incidence was at least 1 per 1000. Conclusion This study showed how routine data can be combined with household survey data to model malaria incidence. The incidence of both P. vivax and P. falciparum in Afghanistan remain low but the co-distribution of both parasites and the lag in their peak season provides challenges to malaria control in Afghanistan. Future improved case definition to determine levels of imported risks may be useful for the elimination ambitions in Afghanistan. PMID:25033452
International Nuclear Information System (INIS)
Skibin, D.
1980-01-01
A general case of release to the atmosphere of a pollutant is considered. In hazards evaluation the processes involved are usually estimated conservatively so as to maximize the computed doses. The present work helps to identify the worst cases. In addition, a model of the total dose is presented and its variations are studied as a function of wind speed, deposition velocity and source height. The value of each parameter giving the highest total dose as a function of the model's parameters is determined. (H.K.)
Murakami, Keiko; Asayama, Kei; Satoh, Michihiro; Hosaka, Miki; Matsuda, Ayako; Inoue, Ryusuke; Tsubota-Utsugi, Megumi; Murakami, Takahisa; Nomura, Kyoko; Kikuya, Masahiro; Metoki, Hirohito; Imai, Yutaka; Ohkubo, Takayoshi
2017-12-01
Several observational studies have found modifying effects of functional status on the association between conventional office blood pressure (BP) and adverse outcomes. We aimed to examine whether the association between higher BP and stroke was attenuated or inverted among older adults with impaired function using self-measured home BP measurements. We followed 501 Japanese community-dwelling adults aged at least 60 years (mean age, 68.6 years) with no history of stroke. Multivariate-adjusted hazard ratios for 1-SD increase in home BP and office BP measurements were calculated by the Cox proportional hazards model. Functional status was assessed by self-reported physical function. During a median follow-up of 11.5 years, first strokes were observed in 47 participants. Higher home SBP, but not office SBP, was significantly associated with increased risk of stroke among both 349 participants with normal physical function and 152 participants with impaired physical function [hazard ratio (95% confidence interval) per 14.4-mmHg increase: 1.74 (1.12-2.69) and 1.77 (1.06-2.94), respectively], with no significant interaction for physical function (P = 0.56). Higher home DBP, but not office DBP, was also significantly associated with increased risk of stroke (P ≤ 0.029) irrespective of physical function (all P > 0.05 for interaction). Neither home BP nor office BP was significantly associated with all-cause mortality irrespective of physical function. Higher home BP was associated with increased risk of stroke even among those with impaired physical function. Measurements of home BP would be useful for stroke prevention, even after physical function decline.
Directory of Open Access Journals (Sweden)
Peter Scarborough
2016-11-01
Full Text Available Abstract Background The DisMod II model is designed to estimate epidemiological parameters on diseases where measured data are incomplete and has been used to provide estimates of disease incidence for the Global Burden of Disease study. We assessed the external validity of the DisMod II model by comparing modelled estimates of the incidence of first acute myocardial infarction (AMI in England in 2010 with estimates derived from a linked dataset of hospital records and death certificates. Methods Inputs for DisMod II were prevalence rates of ever having had an AMI taken from a population health survey, total mortality rates and AMI mortality rates taken from death certificates. By definition, remission rates were zero. We estimated first AMI incidence in an external dataset from England in 2010 using a linked dataset including all hospital admissions and death certificates since 1998. 95 % confidence intervals were derived around estimates from the external dataset and DisMod II estimates based on sampling variance and reported uncertainty in prevalence estimates respectively. Results Estimates of the incidence rate for the whole population were higher in the DisMod II results than the external dataset (+54 % for men and +26 % for women. Age-specific results showed that the DisMod II results over-estimated incidence for all but the oldest age groups. Confidence intervals for the DisMod II and external dataset estimates did not overlap for most age groups. Conclusion By comparison with AMI incidence rates in England, DisMod II did not achieve external validity for age-specific incidence rates, but did provide global estimates of incidence that are of similar magnitude to measured estimates. The model should be used with caution when estimating age-specific incidence rates.
The importance of regional models in assessing canine cancer incidences in Switzerland.
Boo, Gianluca; Leyk, Stefan; Brunsdon, Christopher; Graf, Ramona; Pospischil, Andreas; Fabrikant, Sara Irina
2018-01-01
Fitting canine cancer incidences through a conventional regression model assumes constant statistical relationships across the study area in estimating the model coefficients. However, it is often more realistic to consider that these relationships may vary over space. Such a condition, known as spatial non-stationarity, implies that the model coefficients need to be estimated locally. In these kinds of local models, the geographic scale, or spatial extent, employed for coefficient estimation may also have a pervasive influence. This is because important variations in the local model coefficients across geographic scales may impact the understanding of local relationships. In this study, we fitted canine cancer incidences across Swiss municipal units through multiple regional models. We computed diagnostic summaries across the different regional models, and contrasted them with the diagnostics of the conventional regression model, using value-by-alpha maps and scalograms. The results of this comparative assessment enabled us to identify variations in the goodness-of-fit and coefficient estimates. We detected spatially non-stationary relationships, in particular, for the variables related to biological risk factors. These variations in the model coefficients were more important at small geographic scales, making a case for the need to model canine cancer incidences locally in contrast to more conventional global approaches. However, we contend that prior to undertaking local modeling efforts, a deeper understanding of the effects of geographic scale is needed to better characterize and identify local model relationships.
Abbasi, Ali; Bakker, Stephan J. L.; Corpeleijn, Eva; van der A, Daphne L.; Gansevoort, Ron T.; Gans, Rijk O. B.; Peelen, Linda M.; van der Schouw, Yvonne T.; Stolk, Ronald P.; Navis, Gerjan; Spijkerman, Annemieke M. W.; Beulens, Joline W. J.
2012-01-01
Background: Liver function tests might predict the risk of type 2 diabetes. An independent study evaluating utility of these markers compared with an existing prediction model is yet lacking. Methods and Findings: We performed a case-cohort study, including random subcohort (6.5%) from 38,379
The incidence and functional consequences of RT-associated cardiac perfusion defects
International Nuclear Information System (INIS)
Marks, Lawrence B.; Yu Xiaoli; Prosnitz, Robert G.; Zhou Sumin; Hardenbergh, Patricia H.; Blazing, Michael; Hollis, Donna; Lind, Pehr; Tisch, Andrea; Wong, Terence Z.; Borges-Neto, Salvador
2005-01-01
Purpose: Radiation therapy (RT) for left-sided breast cancer has been associated with cardiac dysfunction. We herein assess the temporal nature and volume dependence of RT-induced left ventricular perfusion defects and whether these perfusion defects are related to changes in cardiac wall motion or alterations in ejection fraction. Methods: From 1998 to 2001, 114 patients were enrolled onto an IRB-approved prospective clinical study to assess changes in regional and global cardiac function after RT for left-sided breast cancer. Patients were imaged 30 to 60 minutes after injection of technetium 99m sestamibi or tetrofosmin. Post-RT perfusion scans were compared with the pre-RT studies to assess for RT-induced perfusion defects as well as functional changes in wall motion and ejection fraction. Two-tailed Fisher's exact test and the Cochran-Armitage test for linear trends were used for statistical analysis. Results: The incidence of new perfusion defects 6, 12, 18, and 24 months after RT was 27%, 29%, 38%, and 42%, respectively. New defects occurred in approximately 10% to 20% and 50% to 60% of patients with less than 5%, and greater than 5%, of their left ventricle included within the RT fields, respectively (p = 0.33 to 0.00008). The rates of wall motion abnormalities in patients with and without perfusion defects were 12% to 40% versus 0% to 9%, respectively; p values were 0.007 to 0.16, depending on the post-RT interval. Conclusions: Radiation therapy causes volume-dependent perfusion defects in approximately 40% of patients within 2 years of RT. These perfusion defects are associated with corresponding wall-motion abnormalities. Additional study is necessary to better define the long-term functional consequences of RT-induced perfusion defects
Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.
1995-01-01
A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme was computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressirve wave environment such as that usually encountered in a commercial aircraft engine and most laboratory settings.
Cost functions of greenhouse models
International Nuclear Information System (INIS)
Linderoth, H.
2000-01-01
The benchmark is equal to the cost (D) caused by an increase in temperature since the middle of the nineteenth century (T) of nearly 2.5 deg. C. According to mainstream economists, the benchmark is 1-2% of GDP, but very different estimates can also be found. Even though there appears to be agreement among a number of economists that the benchmark is 1-2% of GDP, major differences exist when it comes to estimating D for different sectors. One of the main problems is how to estimate non-market activities. Normally, the benchmark is the best guess, but due to the possibility of catastrophic events this can be considerable smaller than the mean. Certainly, the cost function is skewed to the right. The benchmark is just one point on the cost curve. To a great extent, cost functions are alike in greenhouse models (D = α ''.T'' λ). Cost functions are region and sector dependent in several models. In any case, both α (benchmark) and λ are rough estimates. Besides being dependent on α and λ, the marginal emission cost depends on the discount rate. In fact, because emissions have effects continuing for many years, the discount rate is clearly the most important parameter. (au) (au)
Predictions of Quantum Molecular Dynamical Model between incident energy 50 and 1000 MeV/Nucleon
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Kumar Sanjeev
2015-01-01
Full Text Available In the present work, the Quantum Molecular Dynamical (QMD model is summarized as a useful tool for the incident energy range of 50 to 1000 MeV/nucleon in heavy-ion collisions. The model has reproduced the experimental results of various collaborations such as ALADIN, INDRA, PLASTIC BALL and FOPI upto a high level of accuracy for the phenomena like multifragmentation, collective flow as well as elliptical flow in the above prescribed energy range. The efforts are further in the direction to predict the symmetry energy in the wide incident energy range.
International Nuclear Information System (INIS)
Zhao Xinwen; Ren Xin
2014-01-01
In order to further reduce the misoperation after the faults occurring of nuclear-powered system in marine, the model based on weighted degree of grey incidence of optimized entropy and fault diagnosis system are proposed, and some simulation experiments about the typical faults of steam generator of nuclear-powered system in marine are conducted. And the results show that the diagnosis system based on improved degree of grey incidence model is more stable and its conclusion is right, and can satisfy diagnosis in real time, and higher faults subjection degrees resolving power can be achieved. (authors)
Transfer Function Identification Using Orthogonal Fourier Transform Modeling Functions
Morelli, Eugene A.
2013-01-01
A method for transfer function identification, including both model structure determination and parameter estimation, was developed and demonstrated. The approach uses orthogonal modeling functions generated from frequency domain data obtained by Fourier transformation of time series data. The method was applied to simulation data to identify continuous-time transfer function models and unsteady aerodynamic models. Model fit error, estimated model parameters, and the associated uncertainties were used to show the effectiveness of the method for identifying accurate transfer function models from noisy data.
Cumulative Incidence Function in Studies on the Duration of the Unemployment Exit Process
Directory of Open Access Journals (Sweden)
Bieszk-Stolorz Beata
2017-06-01
Full Text Available When we analyse the employment seeking process, an event that ends the observation of a given individual is their employment. The remaining observations are considered to be censored: the observations concluded before the end of the study or the cases of deregistering for other causes (e.g. old-age pension, taking up residence in a foreign country, starting further education. The act of taking up income-generating work can take various forms: taking up a job, setting up a business or taking advantage of subsidised job programmes. Jobseekers are often deregistered from poviat labour offices because they refuse to take up an offered job or fail to report to the office in due time. All the above events are forms of competing risk. The purpose of this paper is to use the cumulative incidence function to assess the probability of the unemployment exit with regard to different types of the competing risk. When competing-risk events occur, a solution sometimes is used where the remaining endpoint events are considered censored observations. Such a solution leads to an overestimation of probability. The results implicate that the beneficiaries’ will to find employment was not a principal reason for a registering decision. The study is based on the individual data of jobseekers registered in the Poviat Labour Office in Szczecin.
Directory of Open Access Journals (Sweden)
Mirabelli Maria C
2012-03-01
Full Text Available Abstract Background Specific occupations are associated with adverse respiratory health. Inhalation exposures encountered in these jobs may place workers at risk of new-onset respiratory disease. Methods We analyzed data from 8,967 participants from the Atherosclerosis Risk in Communities (ARIC study, a longitudinal cohort study. Participants included in this analysis were free of chronic cough and phlegm, wheezing, asthma, chronic bronchitis, emphysema, and other chronic lung conditions at the baseline examination, when they were aged 45-64 years. Using data collected in the baseline and first follow-up examination, we evaluated associations between occupation and the three-year incidence of cough, phlegm, wheezing, and airway obstruction and changes in forced expiratory volume in one second (FEV1 and forced vital capacity (FVC measured by spirometry. All associations were adjusted for age, cigarettes per day, race, smoking status, and study center. Results During the approximately three-year follow-up, the percentage of participants developing chronic cough was 3%; chronic phlegm, 3%; wheezing, 3%; and airway obstruction, defined as FEV1 1/FVC 1 and FVC were 56 mL and 66 mL, respectively, among men and 40 mL and 52 mL, respectively, among women. Relative to a referent category of managerial and administrative support occupations, elevated risks of new-onset chronic cough and chronic phlegm were observed for mechanics and repairers (chronic cough: RR: 1.81, 95% CI: 1.02, 3.21; chronic phlegm: RR: 2.10, 95% CI: 1.23, 3.57 and cleaning and building service workers (chronic cough: RR: 1.85, 95% CI: 1.01, 3.37; chronic phlegm: RR: 2.28, 95% CI: 1.27, 4.08. Despite the elevated risk of new-onset symptoms, employment in cleaning and building services was associated with attenuated lung function decline, particularly among men, who averaged annual declines in FEV1 and FVC of 14 mL and 23 mL, respectively, less than the declines observed in the
The Threshold of a Stochastic SIRS Model with Vertical Transmission and Saturated Incidence
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Chunjuan Zhu
2017-01-01
Full Text Available The threshold of a stochastic SIRS model with vertical transmission and saturated incidence is investigated. If the noise is small, it is shown that the threshold of the stochastic system determines the extinction and persistence of the epidemic. In addition, we find that if the noise is large, the epidemic still prevails. Finally, numerical simulations are given to illustrate the results.
Extinction and Ergodic Property of Stochastic SIS Epidemic Model with Nonlinear Incidence Rate
Directory of Open Access Journals (Sweden)
Qixing Han
2013-01-01
Full Text Available We investigate a stochastic SIS model with nonlinear incidence rate. We show that there exists a unique nonnegative solution to the system, and condition for the infectious individuals I(t to be extinct is given. Moreover, we prove that the system has ergodic property. Finally, computer simulations are carried out to verify our results.
Implementation of the critical points model in a SFM-FDTD code working in oblique incidence
Energy Technology Data Exchange (ETDEWEB)
Hamidi, M; Belkhir, A; Lamrous, O [Laboratoire de Physique et Chimie Quantique, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Baida, F I, E-mail: omarlamrous@mail.ummto.dz [Departement d' Optique P.M. Duffieux, Institut FEMTO-ST UMR 6174 CNRS Universite de Franche-Comte, 25030 Besancon Cedex (France)
2011-06-22
We describe the implementation of the critical points model in a finite-difference-time-domain code working in oblique incidence and dealing with dispersive media through the split field method. Some tests are presented to validate our code in addition to an application devoted to plasmon resonance of a gold nanoparticles grating.
Wilkins, Stacy Schantz; Bourke, Paula; Salam, Abdul; Akhtar, Naveed; D'Souza, Atlantic; Kamran, Saadat; Bhutta, Zain; Shuaib, Ashfaq
2018-01-01
ABSTRACT Objective Approximately 30% of individuals who initially present with stroke are found to be stroke mimics (SM), with functional/psychological SM (FSM) accounting for up to 6.4% of all stroke presentations. Middle Eastern countries may have higher rates of somatization of emotional distress. The aim of this study was to evaluate the incidence and characteristics of FSM at a large general hospital in the Middle East. Methods All patients presenting with an initial diagnosis of stroke from June 2015 to September 2016 were eligible for this study. Clinical and sociodemographic data were obtained from the hospital's stroke database. All SM and strokes were diagnosed by Joint Commission International–certified stroke program neurologists. SM was defined as any discharge diagnosis (other than acute stroke) for symptoms that prompted initial admission for suspected stroke. FSM were compared with medical stroke mimics (MSM) and strokes (ischemic, hemorrhagic, and transient ischemic attacks). Results A total of 1961 patients were identified; 161 FSM (8.2%), 390 MSM (19.9%), and 1410 strokes (71.9%) (985 ischemic strokes, 196 transient ischemic attacks, 229 intracerebral hemorrhages). Admission with FSM was related to patients' nationality, with the highest frequency in Arabic (15.6%) and African (16.8%) patients. FSM patients were younger, more often female, and had fewer cardiovascular risk factors except for smoking compared with the strokes. FSM patients presented with more left-sided weakness and had more magnetic resonance imagings than the stroke and MSM groups. A total of 9.9% of FSM patients received thrombolysis versus only 0.5% of the MSM and 16.4% of ischemic strokes. Conclusions FSM frequencies varied by nationality, with Arab and African nationals being twice as prevalent. Stress, vulnerable status as expats, sociopolitical instability, and exposure to trauma are proposed as potential factors contributing to FSM. PMID:29394187
Report #18-P-0030, October 30, 2017. Weaknesses in the Identity and Access Management and Incident Response metric domains leave the CSB vulnerable to attacks occurring and not being detected in a timely manner.
Dynamic Behavior for an SIRS Model with Nonlinear Incidence Rate and Treatment
Directory of Open Access Journals (Sweden)
Junhong Li
2013-01-01
Full Text Available This paper considers an SIRS model with nonlinear incidence rate and treatment. It is assumed that susceptible and infectious individuals have constant immigration rates. We investigate the existence of equilibrium and prove the global asymptotical stable results of the endemic equilibrium. We then obtained that the model undergoes a Hopf bifurcation and existences a limit cycle. Some numerical simulations are given to illustrate the analytical results.
International Nuclear Information System (INIS)
Regens, J.L.; Gunter, J.T.; Gupta, S.
2009-01-01
Homeland Security Presidential Directive no.5 (HSPD-5) Management of Domestic Incidents and Department of Homeland Security (DHS) Planning Guidance for Protection and Recovery Following Radiological Dispersal Device (RDD) and Improvised Nuclear Device (IND) Incidents underscore the need to delineate radiological emergency guidance applicable to remedial action and recovery following an RDD or IND incident. Rapid delineation of the population potentially exposed to ionizing radiation from fallout during terrorist incidents involving RDDs or low-yield nuclear devices (≤ 20 KT) is necessary for effective medical response and incident management as part of the recovery process. This paper illustrates the application of spatial interaction models to allocate population data for a representative U.S. urban area (≅1.3M people; 1,612.27 km 2 area) at a geographical scale relevant for accurately estimating risk given dose concentrations. Estimated total dose equivalents (TEDE) are calculated for isopleths moving away from the detonation point for typical release scenarios. Population is estimated within the TEDE zones using Euclidean distances between zip code polygon centroids generated in ArcGIS version 9.1 with distance decay determined by regression analysis to apportion origin-destination pairs to a population count and density matrix on a spatial basis for daytime and night-time release scenarios. (authors)
Schultheiss, Ulla T; Daya, Natalie; Grams, Morgan E; Seufert, Jochen; Steffes, Michael; Coresh, Josef; Selvin, Elizabeth; Köttgen, Anna
2017-11-01
Reduced kidney function is a common public health problem that increases risk for a wide variety of adverse outcomes, making the identification of potentially modifiable factors associated with the development of incident chronic kidney disease (CKD) important. Alterations in the hypothalamic-pituitary-thyroid axis have been linked to reduced kidney function, but the association of thyroid function with the development of incident CKD is largely uncharacterized. Concentrations of thyroid stimulating hormone (TSH), free thyroxine (FT4), triiodothyronine (T3) and thyroid peroxidase antibody (TPOAb) were quantified in 12 785 black and white participants of the ongoing community-based prospective Atherosclerosis Risk in Communities study. Thyroid markers and clinical categories of thyroid dysfunction (euthyroidism, combined subclinical and overt hypothyroidism, combined subclinical and overt hyperthyroidism) were also evaluated for their association with reduced kidney function (estimated glomerular filtration rate kidney function at study baseline. The clinical entities hypothyroidism and hyperthyroidism were also associated with higher odds of baseline reduced kidney function, but this was not significant. However, none of the markers of thyroid function nor different clinical categories of thyroid dysfunction (hypothyroidism, hyperthyroidism or TPOAb positivity) were associated with incident CKD in adjusted analyses. Elevated TSH, FT4 and reduced T3 concentrations were associated with reduced kidney function cross-sectionally. The lack of association with the development of incident CKD suggests that altered thyroid function in the general population is not causally related to CKD development, but screening for thyroidal status may be especially relevant in persons with reduced kidney function. © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.
Analysis of an HIV/AIDS treatment model with a nonlinear incidence
International Nuclear Information System (INIS)
Cai Liming; Wu Jingang
2009-01-01
An HIV/AIDS treatment model with a nonlinear incidence is formulated. The infectious period is partitioned into the asymptotic and the symptomatic phases according to clinical stages. The constant recruitment rate, disease-induced death, drug therapies, as well as a nonlinear incidence, are incorporated into the model. The basic reproduction number R 0 of the model is determined by the method of next generation matrix. Mathematical analysis establishes that the global dynamics of the spread of the HIV infectious disease are completely determined by the basic reproduction number R 0 . If R 0 ≤1, the disease always dies out and the disease-free equilibrium is globally stable. If R 0 >1, the disease persists and the unique endemic equilibrium is globally asymptotically stable in the interior of the feasible region.
The Smo/Smo model: hedgehog-induced medulloblastoma with 90% incidence and leptomeningeal spread.
Hatton, Beryl A; Villavicencio, Elisabeth H; Tsuchiya, Karen D; Pritchard, Joel I; Ditzler, Sally; Pullar, Barbara; Hansen, Stacey; Knoblaugh, Sue E; Lee, Donghoon; Eberhart, Charles G; Hallahan, Andrew R; Olson, James M
2008-03-15
Toward the goal of generating a mouse medulloblastoma model with increased tumor incidence, we developed a homozygous version of our ND2:SmoA1 model. Medulloblastomas form in 94% of homozygous Smo/Smo mice by 2 months of age. Tumor formation is, thus, predictable by age, before the symptomatic appearance of larger lesions. This high incidence and early onset of tumors is ideal for preclinical studies because mice can be enrolled before symptom onset and with a greater latency period before late-stage disease. Smo/Smo tumors also display leptomeningeal dissemination of neoplastic cells to the brain and spine, which occurs in many human cases. Despite an extended proliferation of granule neuron precursors (GNP) in the postnatal external granular layer (EGL), the internal granular layer formed normally in Smo/Smo mice and tumor formation occurred only in localized foci on the superficial surface of the molecular layer. Thus, tumor formation is not simply the result of over proliferation of GNPs within the EGL. Moreover, Smo/Smo medulloblastomas were transplantable and serially passaged in vivo, demonstrating the aggressiveness of tumor cells and their transformation beyond a hyperplastic state. The Smo/Smo model is the first mouse medulloblastoma model to show leptomeningeal spread. The adherence to human pathology, high incidence, and early onset of tumors thus make Smo/Smo mice an efficient model for preclinical studies.
Modeling the incidence of citrus canker in leaves of the sweet orange variety ‘Pera’
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Danielle da Silva Pompeu
2017-01-01
Full Text Available Citrus canker, caused by the bacterium Xanthomonas citri subsp. citri, is one of the most important diseases of citrus. The use of resistant genotypes plays an important role in the management and control of the disease and is the most environmentally sustainable approach to disease control. Citrus canker incidence was recorded in an experiment on nine genotypes of the sweet orange variety ‘Pera’ grafted on four rootstocks. The experiment was started in 2010 and the incidence of citrus canker on the leaves was recorded on a quarterly basis. The incidence data from the experiment were analyzed using a zero-inflated Beta regression model (RBIZ, which is the appropriate method to describe data with large numbers of zeros. Based on the residual analysis, the data fit the model well. The discrete component of the explanatory variable, rootstock, was not significant as a factor affecting the onset of disease, in contrast with the continuous component, genotype, which was significant in explaining the incidence of citrus canker.
Function Model for Community Health Service Information
Yang, Peng; Pan, Feng; Liu, Danhong; Xu, Yongyong
In order to construct a function model of community health service (CHS) information for development of CHS information management system, Integration Definition for Function Modeling (IDEF0), an IEEE standard which is extended from Structured Analysis and Design(SADT) and now is a widely used function modeling method, was used to classifying its information from top to bottom. The contents of every level of the model were described and coded. Then function model for CHS information, which includes 4 super-classes, 15 classes and 28 sub-classed of business function, 43 business processes and 168 business activities, was established. This model can facilitate information management system development and workflow refinement.
Global Stability of an Eco-Epidemiological Model with Time Delay and Saturation Incidence
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Shuxue Mao
2011-01-01
Full Text Available We investigate a delayed eco-epidemiological model with disease in predator and saturation incidence. First, by comparison arguments, the permanence of the model is discussed. Then, we study the local stability of each equilibrium of the model by analyzing the corresponding characteristic equations and find that Hopf bifurcation occurs when the delay τ passes through a sequence of critical values. Next, by means of an iteration technique, sufficient conditions are derived for the global stability of the disease-free planar equilibrium and the positive equilibrium. Numerical examples are carried out to illustrate the analytical results.
DEFF Research Database (Denmark)
Rossing, K; Jacobsen, P; Rossing, P
1998-01-01
OBJECTIVE: To evaluate trends in visual acuity and the cumulative incidence of diabetic retinopathy in a clinic-based observational follow-up study. RESEARCH DESIGN AND METHODS: All patients visiting Hvidore Hospital in 1984 whose diagnosis of IDDM had been made before 41 years of age and between...
Directory of Open Access Journals (Sweden)
Andrew I. Chin
2017-09-01
Discussion: More than 50% of incident HD patients with RKF have adequate kidney urea clearance to be considered for 2-times weekly HD. When additionally ultrafiltration volume and blood pressure stability are taken into account, more than one-fourth of the total cohort could optimally start HD in an incremental fashion.
Multi-step polynomial regression method to model and forecast malaria incidence.
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Chandrajit Chatterjee
Full Text Available Malaria is one of the most severe problems faced by the world even today. Understanding the causative factors such as age, sex, social factors, environmental variability etc. as well as underlying transmission dynamics of the disease is important for epidemiological research on malaria and its eradication. Thus, development of suitable modeling approach and methodology, based on the available data on the incidence of the disease and other related factors is of utmost importance. In this study, we developed a simple non-linear regression methodology in modeling and forecasting malaria incidence in Chennai city, India, and predicted future disease incidence with high confidence level. We considered three types of data to develop the regression methodology: a longer time series data of Slide Positivity Rates (SPR of malaria; a smaller time series data (deaths due to Plasmodium vivax of one year; and spatial data (zonal distribution of P. vivax deaths for the city along with the climatic factors, population and previous incidence of the disease. We performed variable selection by simple correlation study, identification of the initial relationship between variables through non-linear curve fitting and used multi-step methods for induction of variables in the non-linear regression analysis along with applied Gauss-Markov models, and ANOVA for testing the prediction, validity and constructing the confidence intervals. The results execute the applicability of our method for different types of data, the autoregressive nature of forecasting, and show high prediction power for both SPR and P. vivax deaths, where the one-lag SPR values plays an influential role and proves useful for better prediction. Different climatic factors are identified as playing crucial role on shaping the disease curve. Further, disease incidence at zonal level and the effect of causative factors on different zonal clusters indicate the pattern of malaria prevalence in the city
Traveling waves in a delayed SIR model with nonlocal dispersal and nonlinear incidence
Zhang, Shou-Peng; Yang, Yun-Rui; Zhou, Yong-Hui
2018-01-01
This paper is concerned with traveling waves of a delayed SIR model with nonlocal dispersal and a general nonlinear incidence. The existence and nonexistence of traveling waves of the system are established respectively by Schauder's fixed point theorem and two-sided Laplace transform. It is also shown that the spread speed c is influenced by the dispersal rate of the infected individuals and the delay τ.
Gaudart, Jean; Touré, Ousmane; Dessay, Nadine; Dicko, A Lassane; Ranque, Stéphane; Forest, Loic; Demongeot, Jacques; Doumbo, Ogobara K
2009-04-10
The risk of Plasmodium falciparum infection is variable over space and time and this variability is related to environmental variability. Environmental factors affect the biological cycle of both vector and parasite. Despite this strong relationship, environmental effects have rarely been included in malaria transmission models.Remote sensing data on environment were incorporated into a temporal model of the transmission, to forecast the evolution of malaria epidemiology, in a locality of Sudanese savannah area. A dynamic cohort was constituted in June 1996 and followed up until June 2001 in the locality of Bancoumana, Mali. The 15-day composite vegetation index (NDVI), issued from satellite imagery series (NOAA) from July 1981 to December 2006, was used as remote sensing data.The statistical relationship between NDVI and incidence of P. falciparum infection was assessed by ARIMA analysis. ROC analysis provided an NDVI value for the prediction of an increase in incidence of parasitaemia.Malaria transmission was modelled using an SIRS-type model, adapted to Bancoumana's data. Environmental factors influenced vector mortality and aggressiveness, as well as length of the gonotrophic cycle. NDVI observations from 1981 to 2001 were used for the simulation of the extrinsic variable of a hidden Markov chain model. Observations from 2002 to 2006 served as external validation. The seasonal pattern of P. falciparum incidence was significantly explained by NDVI, with a delay of 15 days (p = 0.001). An NDVI threshold of 0.361 (p = 0.007) provided a Diagnostic Odd Ratio (DOR) of 2.64 (CI95% [1.26;5.52]).The deterministic transmission model, with stochastic environmental factor, predicted an endemo-epidemic pattern of malaria infection. The incidences of parasitaemia were adequately modelled, using the observed NDVI as well as the NDVI simulations. Transmission pattern have been modelled and observed values were adequately predicted. The error parameters have shown the smallest
Directory of Open Access Journals (Sweden)
Demongeot Jacques
2009-04-01
Full Text Available Abstract Background The risk of Plasmodium falciparum infection is variable over space and time and this variability is related to environmental variability. Environmental factors affect the biological cycle of both vector and parasite. Despite this strong relationship, environmental effects have rarely been included in malaria transmission models. Remote sensing data on environment were incorporated into a temporal model of the transmission, to forecast the evolution of malaria epidemiology, in a locality of Sudanese savannah area. Methods A dynamic cohort was constituted in June 1996 and followed up until June 2001 in the locality of Bancoumana, Mali. The 15-day composite vegetation index (NDVI, issued from satellite imagery series (NOAA from July 1981 to December 2006, was used as remote sensing data. The statistical relationship between NDVI and incidence of P. falciparum infection was assessed by ARIMA analysis. ROC analysis provided an NDVI value for the prediction of an increase in incidence of parasitaemia. Malaria transmission was modelled using an SIRS-type model, adapted to Bancoumana's data. Environmental factors influenced vector mortality and aggressiveness, as well as length of the gonotrophic cycle. NDVI observations from 1981 to 2001 were used for the simulation of the extrinsic variable of a hidden Markov chain model. Observations from 2002 to 2006 served as external validation. Results The seasonal pattern of P. falciparum incidence was significantly explained by NDVI, with a delay of 15 days (p = 0.001. An NDVI threshold of 0.361 (p = 0.007 provided a Diagnostic Odd Ratio (DOR of 2.64 (CI95% [1.26;5.52]. The deterministic transmission model, with stochastic environmental factor, predicted an endemo-epidemic pattern of malaria infection. The incidences of parasitaemia were adequately modelled, using the observed NDVI as well as the NDVI simulations. Transmission pattern have been modelled and observed values were adequately
Gaudart, Jean; Touré, Ousmane; Dessay, Nadine; Dicko, A lassane; Ranque, Stéphane; Forest, Loic; Demongeot, Jacques; Doumbo, Ogobara K
2009-01-01
Background The risk of Plasmodium falciparum infection is variable over space and time and this variability is related to environmental variability. Environmental factors affect the biological cycle of both vector and parasite. Despite this strong relationship, environmental effects have rarely been included in malaria transmission models. Remote sensing data on environment were incorporated into a temporal model of the transmission, to forecast the evolution of malaria epidemiology, in a locality of Sudanese savannah area. Methods A dynamic cohort was constituted in June 1996 and followed up until June 2001 in the locality of Bancoumana, Mali. The 15-day composite vegetation index (NDVI), issued from satellite imagery series (NOAA) from July 1981 to December 2006, was used as remote sensing data. The statistical relationship between NDVI and incidence of P. falciparum infection was assessed by ARIMA analysis. ROC analysis provided an NDVI value for the prediction of an increase in incidence of parasitaemia. Malaria transmission was modelled using an SIRS-type model, adapted to Bancoumana's data. Environmental factors influenced vector mortality and aggressiveness, as well as length of the gonotrophic cycle. NDVI observations from 1981 to 2001 were used for the simulation of the extrinsic variable of a hidden Markov chain model. Observations from 2002 to 2006 served as external validation. Results The seasonal pattern of P. falciparum incidence was significantly explained by NDVI, with a delay of 15 days (p = 0.001). An NDVI threshold of 0.361 (p = 0.007) provided a Diagnostic Odd Ratio (DOR) of 2.64 (CI95% [1.26;5.52]). The deterministic transmission model, with stochastic environmental factor, predicted an endemo-epidemic pattern of malaria infection. The incidences of parasitaemia were adequately modelled, using the observed NDVI as well as the NDVI simulations. Transmission pattern have been modelled and observed values were adequately predicted. The error
International Nuclear Information System (INIS)
Badano, Aldo; Freed, Melanie; Fang Yuan
2011-01-01
Purpose: The authors describe the modifications to a previously developed analytical model of indirect CsI:Tl-based detector response required for studying oblique x-ray incidence effects in direct semiconductor-based detectors. This first-order approximation analysis allows the authors to describe the associated degradation in resolution in direct detectors and compare the predictions to the published data for indirect detectors. Methods: The proposed model is based on a physics-based analytical description developed by Freed et al. [''A fast, angle-dependent, analytical model of CsI detector response for optimization of 3D x-ray breast imaging systems,'' Med. Phys. 37(6), 2593-2605 (2010)] that describes detector response functions for indirect detectors and oblique incident x rays. The model, modified in this work to address direct detector response, describes the dependence of the response with x-ray energy, thickness of the transducer layer, and the depth-dependent blur and collection efficiency. Results: The authors report the detector response functions for indirect and direct detector models for typical thicknesses utilized in clinical systems for full-field digital mammography (150 μm for indirect CsI:Tl and 200 μm for a-Se direct detectors). The results suggest that the oblique incidence effect in a semiconductor detector differs from that in indirect detectors in two ways: The direct detector model produces a sharper overall PRF compared to the response corresponding to the indirect detector model for normal x-ray incidence and a larger relative increase in blur along the x-ray incidence direction compared to that found in indirect detectors with respect to the response at normal incidence angles. Conclusions: Compared to the effect seen in indirect detectors, the direct detector model exhibits a sharper response at normal x-ray incidence and a larger relative increase in blur along the x-ray incidence direction with respect to the blur in the
Functional State Modelling of Saccharomyces cerevisiae Cultivations
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Iasen Hristozov
2004-10-01
Full Text Available The implementation of functional state approach for modelling of yeast cultivation is considered in this paper. This concept helps in monitoring and control of complex processes such as bioprocesses. Using of functional state modelling approach for fermentation processes aims to overcome the main disadvantage of using global process model, namely complex model structure and big number of model parameters. The main advantage of functional state modelling is that the parameters of each local model can be separately estimated from other local models parameters. The results achieved from batch, as well as from fed-batch, cultivations are presented.
Modeling the microstructure of surface by applying BRDF function
Plachta, Kamil
2017-06-01
The paper presents the modeling of surface microstructure using a bidirectional reflectance distribution function. This function contains full information about the reflectance properties of the flat surfaces - it is possible to determine the share of the specular, directional and diffuse components in the reflected luminous stream. The software is based on the authorial algorithm that uses selected elements of this function models, which allows to determine the share of each component. Basing on obtained data, the surface microstructure of each material can be modeled, which allows to determine the properties of this materials. The concentrator directs the reflected solar radiation onto the photovoltaic surface, increasing, at the same time, the value of the incident luminous stream. The paper presents an analysis of selected materials that can be used to construct the solar concentrator system. The use of concentrator increases the power output of the photovoltaic system by up to 17% as compared to the standard solution.
Structure functions from chiral soliton models
International Nuclear Information System (INIS)
Weigel, H.; Reinhardt, H.; Gamberg, L.
1997-01-01
We study nucleon structure functions within the bosonized Nambu-Jona-Lasinio (NJL) model where the nucleon emerges as a chiral soliton. We discuss the model predictions on the Gottfried sum rule for electron-nucleon scattering. A comparison with a low-scale parametrization shows that the model reproduces the gross features of the empirical structure functions. We also compute the leading twist contributions of the polarized structure functions g 1 and g 2 in this model. We compare the model predictions on these structure functions with data from the E143 experiment by GLAP evolving them from the scale characteristic for the NJL-model to the scale of the data
Auais, Mohammad; French, Simon; Alvarado, Beatriz; Pirkle, Catherine; Belanger, Emmanuelle; Guralnik, Jack
2017-12-06
To study the extent to which fear of falling (FOF) is associated with the onset of functional disability over a 2-year period in older adults using self-reported and performance-based measures. In 2012, 1,601 participants (aged 65-74) were recruited from four sites: Kingston and Saint-Hyacinthe, Canada; Manizales, Colombia; and Natal, Brazil. They were re-assessed in 2014. We quantified FOF using the Fall Efficacy Scale-International (FES-I; range: 16-64). Functional disability measures were 1) self-reported incident mobility disability, defined as difficulty climbing a flight of stairs or walking 400 meters and 2) incident poor physical performance, defined as a score <9 on the Short Physical Performance Battery. In the Poisson regression analysis, we included only those participants without functional disability at baseline to calculate incident risk ratios in 2014. 1,355 participants completed the 2014 assessment, of which 917 and 1,078 had no mobility disability and poor physical performance at baseline, respectively. In 2014, 131 (14.3%), and 166 (15.4%) participants reported incident mobility disability and poor physical performance, respectively. After adjusting for age, sex, socioeconomic, and health covariates, a one-point increase in FES-I at baseline was associated with a 4% increase in the risk of reporting incident mobility disability (95% CI: 1.02-1.05) and a 3% increase in the risk of developing poor physical performance at follow up in the overall sample (95%CI: 1.01-1.05). FOF is associated with a higher risk of incident mobility disability and poor physical performance in a cohort of older adults. It is increasingly important to study FOF's effect on functional disability and to take necessary measures to prevent the transition to end-stage disability. © The Author(s) 2017. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Directory of Open Access Journals (Sweden)
Tengiz Mdzinarishvili
2009-12-01
Full Text Available A simple, computationally efficient procedure for analyses of the time period and birth cohort effects on the distribution of the age-specific incidence rates of cancers is proposed. Assuming that cohort effects for neighboring cohorts are almost equal and using the Log-Linear Age-Period-Cohort Model, this procedure allows one to evaluate temporal trends and birth cohort variations of any type of cancer without prior knowledge of the hazard function. This procedure was used to estimate the influence of time period and birth cohort effects on the distribution of the age-specific incidence rates of first primary, microscopically confirmed lung cancer (LC cases from the SEER9 database. It was shown that since 1975, the time period effect coefficients for men increase up to 1980 and then decrease until 2004. For women, these coefficients increase from 1975 up to 1990 and then remain nearly constant. The LC birth cohort effect coefficients for men and women increase from the cohort of 1890–94 until the cohort of 1925–29, then decrease until the cohort of 1950–54 and then remain almost unchanged. Overall, LC incidence rates, adjusted by period and cohort effects, increase up to the age of about 72–75, turn over, and then fall after the age of 75–78. The peak of the adjusted rates in men is around the age of 77–78, while in women, it is around the age of 72–73. Therefore, these results suggest that the age distribution of the incidence rates in men and women fall at old ages.
Bifurcation analysis of a discrete SIS model with bilinear incidence depending on new infection.
Cao, Hui; Zhou, Yicang; Ma, Zhien
2013-01-01
A discrete SIS epidemic model with the bilinear incidence depending on the new infection is formulated and studied. The condition for the global stability of the disease free equilibrium is obtained. The existence of the endemic equilibrium and its stability are investigated. More attention is paid to the existence of the saddle-node bifurcation, the flip bifurcation, and the Hopf bifurcation. Sufficient conditions for those bifurcations have been obtained. Numerical simulations are conducted to demonstrate our theoretical results and the complexity of the model.
Value function in economic growth model
Bagno, Alexander; Tarasyev, Alexandr A.; Tarasyev, Alexander M.
2017-11-01
Properties of the value function are examined in an infinite horizon optimal control problem with an unlimited integrand index appearing in the quality functional with a discount factor. Optimal control problems of such type describe solutions in models of economic growth. Necessary and sufficient conditions are derived to ensure that the value function satisfies the infinitesimal stability properties. It is proved that value function coincides with the minimax solution of the Hamilton-Jacobi equation. Description of the growth asymptotic behavior for the value function is provided for the logarithmic, power and exponential quality functionals and an example is given to illustrate construction of the value function in economic growth models.
Threshold Dynamics in Stochastic SIRS Epidemic Models with Nonlinear Incidence and Vaccination
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Lei Wang
2017-01-01
Full Text Available In this paper, the dynamical behaviors for a stochastic SIRS epidemic model with nonlinear incidence and vaccination are investigated. In the models, the disease transmission coefficient and the removal rates are all affected by noise. Some new basic properties of the models are found. Applying these properties, we establish a series of new threshold conditions on the stochastically exponential extinction, stochastic persistence, and permanence in the mean of the disease with probability one for the models. Furthermore, we obtain a sufficient condition on the existence of unique stationary distribution for the model. Finally, a series of numerical examples are introduced to illustrate our main theoretical results and some conjectures are further proposed.
Lennquist Montán, K; Hreckovski, B; Dobson, B; Örtenwall, P; Montán, C; Khorram-Manesh, A; Lennquist, S
2014-08-01
The need for and benefit of simulation models for interactive training of the response to major incidents and disasters has been increasingly recognized during recent years. One of the advantages with such models is that all components of the chain of response can be trained simultaneously. This includes the important communication/coordination between different units, which has been reported as the most common cause of failure. Very few of the presently available simulation models have been suitable for the simultaneous training of decision-making on all levels of the response. In this study, a new simulation model, originally developed for the scientific evaluation of methodology, was adapted to and developed for the postgraduate courses in Medical Response to Major Incidents (MRMI) organized under the auspices of the European Society for Trauma and Emergency Surgery (ESTES). The aim of the present study was to describe this development process, the model it resulted in, and the evaluation of this model. The simulation model was based on casualty cards giving all information normally available for the triage and primary management of traumatized patients. The condition of the patients could be changed by the instructor according to the time passed since the time of injury and treatments performed. Priority of the casualties as well as given treatments could be indicated on the cards by movable markers, which also gave the time required for every treatment. The exercises were run with real consumption of time and resources for all measures performed. The magnetized cards were moved by the trainees through the scene, through the transport lines, and through the hospitals where all functions were trained. For every patient was given the definitive diagnosis and the times within certain treatments had to be done to avoid preventable mortality and complications, which could be related to trauma-scores. The methodology was tested in nine MRMI courses with a total of
Proposing a Compartmental Model for Leprosy and Parameterizing Using Regional Incidence in Brazil.
Smith, Rebecca Lee
2016-08-01
Hansen's disease (HD), or leprosy, is still considered a public health risk in much of Brazil. Understanding the dynamics of the infection at a regional level can aid in identification of targets to improve control. A compartmental continuous-time model for leprosy dynamics was designed based on understanding of the biology of the infection. The transmission coefficients for the model and the rate of detection were fit for each region using Approximate Bayesian Computation applied to paucibacillary and multibacillary incidence data over the period of 2000 to 2010, and model fit was validated on incidence data from 2011 to 2012. Regional variation was noted in detection rate, with cases in the Midwest estimated to be infectious for 10 years prior to detection compared to 5 years for most other regions. Posterior predictions for the model estimated that elimination of leprosy as a public health risk would require, on average, 44-45 years in the three regions with the highest prevalence. The model is easily adaptable to other settings, and can be studied to determine the efficacy of improved case finding on leprosy control.
A forecasting model for dengue incidence in the District of Gampaha, Sri Lanka.
Withanage, Gayan P; Viswakula, Sameera D; Nilmini Silva Gunawardena, Y I; Hapugoda, Menaka D
2018-04-24
Dengue is one of the major health problems in Sri Lanka causing an enormous social and economic burden to the country. An accurate early warning system can enhance the efficiency of preventive measures. The aim of the study was to develop and validate a simple accurate forecasting model for the District of Gampaha, Sri Lanka. Three time-series regression models were developed using monthly rainfall, rainy days, temperature, humidity, wind speed and retrospective dengue incidences over the period January 2012 to November 2015 for the District of Gampaha, Sri Lanka. Various lag times were analyzed to identify optimum forecasting periods including interactions of multiple lags. The models were validated using epidemiological data from December 2015 to November 2017. Prepared models were compared based on Akaike's information criterion, Bayesian information criterion and residual analysis. The selected model forecasted correctly with mean absolute errors of 0.07 and 0.22, and root mean squared errors of 0.09 and 0.28, for training and validation periods, respectively. There were no dengue epidemics observed in the district during the training period and nine outbreaks occurred during the forecasting period. The proposed model captured five outbreaks and correctly rejected 14 within the testing period of 24 months. The Pierce skill score of the model was 0.49, with a receiver operating characteristic of 86% and 92% sensitivity. The developed weather based forecasting model allows warnings of impending dengue outbreaks and epidemics in advance of one month with high accuracy. Depending upon climatic factors, the previous month's dengue cases had a significant effect on the dengue incidences of the current month. The simple, precise and understandable forecasting model developed could be used to manage limited public health resources effectively for patient management, vector surveillance and intervention programmes in the district.
Kidney Function, Proteinuria, and Cancer Incidence: The Korean Heart Study.
Mok, Yejin; Matsushita, Kunihiro; Ballew, Shoshana H; Sang, Yingying; Jung, Keum Ji; Lee, Sunmi; Jee, Sun Ha; Coresh, Josef
2017-10-01
Reported associations of estimated glomerular filtration rate (eGFR) with cancer risk are inconsistent, and data for the proteinuria-cancer relationship are sparse. We sought to quantify the associations of cancer incidence with eGFR and with proteinuria in a large population-based cohort. A prospective cohort study. 242,583 adults (30-74 years old) without a diagnosis of cancer at baseline in the Korean Heart Study, based on health checkups in 1996 to 2004 with follow-up until 2012. Creatinine-based eGFR (≥90, 60-89, 45-59, and cancer incidence based on ICD-10 codes. 15,165 cases of cancer were detected. The relationship between eGFR and incidence of any cancer was J shaped, with the lowest risk at 45 to 59mL/min/1.73m 2 . There was 44% higher risk for any cancer among those with eGFRscancer risk, showing a dose-response relationship (HRs of 1.24 [95% CI, 1.13-1.35], 1.38 [95% CI, 1.17-1.63], and 1.66 [95% CI, 1.30-2.12] for 1+, 2+, and ≥3+ vs undetectable/trace). Examining site-specific cancer, eGFRkidney and ureteral cancer, multiple myeloma, and leukemia, whereas proteinuria ≥ 1+ (vs undetectable/trace) was related to a broader set of cancers (ie, stomach, rectal, liver, lung, ovarian, kidney, bladder, and multiple myeloma). After excluding study participants with follow-up less than 3 years, the associations remained consistent for kidney cancer and myeloma with eGFR and for rectal, liver, lung, and ovarian cancer with proteinuria. Relatively small number of participants with severely reduced eGFR or 70 years or older. Kidney measures, particularly proteinuria, were associated with increased incidence of cancer. Future studies are needed to better understand the pathophysiologic mechanisms underlying these associations. Copyright © 2017 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2011-01-01
resistivity and the absorber thickness on the difference between the two surface reaction models are examined and discussed. For a porous absorber backed by a rigid surface, the local reaction models give errors of less than 10% if the thickness exceeds 120 mm for a flow resistivity of 5000 Nm-4s. As the flow...... incidence acoustical characteristics of typical building elements made of porous materials assuming extended and local reaction. For each surface reaction, five well-established wave propagation models, the Delany-Bazley, Miki, Beranek, Allard-Champoux, and Biot model, are employed. Effects of the flow...... resistivity doubles, a decrease in the required thickness by 25 mm is observed to achieve the same amount of error. For an absorber backed by an air gap, the thickness ratio between the material and air cavity is important. If the absorber thickness is approximately 40% of the cavity depth, the local reaction...
Cawiding, Olive R.; Natividad, Gina May R.; Bato, Crisostomo V.; Addawe, Rizavel C.
2017-11-01
The prevalence of typhoid fever in developing countries such as the Philippines calls for a need for accurate forecasting of the disease. This will be of great assistance in strategic disease prevention. This paper presents a development of useful models that predict the behavior of typhoid fever incidence based on the monthly incidence in the provinces of the Cordillera Administrative Region from 2010 to 2015 using univariate time series analysis. The data used was obtained from the Cordillera Office of the Department of Health (DOH-CAR). Seasonal autoregressive moving average (SARIMA) models were used to incorporate the seasonality of the data. A comparison of the results of the obtained models revealed that the SARIMA (1,1,7)(0,0,1)12 with a fixed coefficient at the seventh lag produces the smallest root mean square error (RMSE), mean absolute error (MAE), Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). The model suggested that for the year 2016, the number of cases would increase from the months of July to September and have a drop in December. This was then validated using the data collected from January 2016 to December 2016.
Modelling psychological responses to the Great East Japan earthquake and nuclear incident.
Goodwin, Robin; Takahashi, Masahito; Sun, Shaojing; Gaines, Stanley O
2012-01-01
The Great East Japan (Tōhoku/Kanto) earthquake of March 2011 was followed by a major tsunami and nuclear incident. Several previous studies have suggested a number of psychological responses to such disasters. However, few previous studies have modelled individual differences in the risk perceptions of major events, or the implications of these perceptions for relevant behaviours. We conducted a survey specifically examining responses to the Great Japan earthquake and nuclear incident, with data collected 11-13 weeks following these events. 844 young respondents completed a questionnaire in three regions of Japan; Miyagi (close to the earthquake and leaking nuclear plants), Tokyo/Chiba (approximately 220 km from the nuclear plants), and Western Japan (Yamaguchi and Nagasaki, some 1000 km from the plants). Results indicated significant regional differences in risk perception, with greater concern over earthquake risks in Tokyo than in Miyagi or Western Japan. Structural equation analyses showed that shared normative concerns about earthquake and nuclear risks, conservation values, lack of trust in governmental advice about the nuclear hazard, and poor personal control over the nuclear incident were positively correlated with perceived earthquake and nuclear risks. These risk perceptions further predicted specific outcomes (e.g. modifying homes, avoiding going outside, contemplating leaving Japan). The strength and significance of these pathways varied by region. Mental health and practical implications of these findings are discussed in the light of the continuing uncertainties in Japan following the March 2011 events.
Modelling psychological responses to the Great East Japan earthquake and nuclear incident.
Directory of Open Access Journals (Sweden)
Robin Goodwin
Full Text Available The Great East Japan (Tōhoku/Kanto earthquake of March 2011 was followed by a major tsunami and nuclear incident. Several previous studies have suggested a number of psychological responses to such disasters. However, few previous studies have modelled individual differences in the risk perceptions of major events, or the implications of these perceptions for relevant behaviours. We conducted a survey specifically examining responses to the Great Japan earthquake and nuclear incident, with data collected 11-13 weeks following these events. 844 young respondents completed a questionnaire in three regions of Japan; Miyagi (close to the earthquake and leaking nuclear plants, Tokyo/Chiba (approximately 220 km from the nuclear plants, and Western Japan (Yamaguchi and Nagasaki, some 1000 km from the plants. Results indicated significant regional differences in risk perception, with greater concern over earthquake risks in Tokyo than in Miyagi or Western Japan. Structural equation analyses showed that shared normative concerns about earthquake and nuclear risks, conservation values, lack of trust in governmental advice about the nuclear hazard, and poor personal control over the nuclear incident were positively correlated with perceived earthquake and nuclear risks. These risk perceptions further predicted specific outcomes (e.g. modifying homes, avoiding going outside, contemplating leaving Japan. The strength and significance of these pathways varied by region. Mental health and practical implications of these findings are discussed in the light of the continuing uncertainties in Japan following the March 2011 events.
Aungaroon, Gewalin; Zea Vera, Alonso; Horn, Paul S; Byars, Anna W; Greiner, Hansel M; Tenney, Jeffrey R; Arthur, Todd M; Crone, Nathan E; Holland, Katherine D; Mangano, Francesco T; Arya, Ravindra
2017-10-01
This study examined the incidence, thresholds, and determinants of electrical cortical stimulation (ECS)-induced after-discharges (ADs) and seizures. Electrocorticograph recordings were reviewed to determine incidence of ECS-induced ADs and seizures. Multivariable analyses for predictors of AD/seizure occurrence and their thresholds were performed. In 122 patients, the incidence of ADs and seizures was 77% (94/122) and 35% (43/122) respectively. Males (odds ratio [OR] 2.92, 95% CI 1.21-7.38, p=0.02) and MRI-negative patients (OR 3.69, 95% CI 1.24-13.7, p=0.03) were found to have higher odds of ECS-induced ADs. A significant trend for decreasing AD thresholds with age was seen (regression co-efficient -0.151, 95% CI -0.267 to -0.035, p=0.011). ECS-induced seizures were more likely in patients with lateralized functional imaging (OR 6.62, 95% CI 1.36-55.56, p=0.036, for positron emission tomography) and presence of ADs (OR 3.50, 95% CI 1.12-13.36, p=0.043). ECS is associated with a high incidence of ADs and seizures. With age, current thresholds decrease and the probability for AD/seizure occurrence increases. ADs and seizures during ECS brain mapping are potentially hazardous and affect its functional validity. Thus, safer method(s) for brain mapping with improved neurophysiologic validity are desirable. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.
Sun, Kai; Hong, Fu; Wang, Yun; Agopian, Vatche G; Yan, Min; Busuttil, Ronald W; Steadman, Randolph H; Xia, Victor W
2017-11-01
Although the hemodynamic benefits of venovenous bypass (VVB) during liver transplantation (LT) are well appreciated, the impact of VVB on posttransplant renal function is uncertain. The aim of this study was to determine if VVB was associated with a lower incidence of posttransplant acute kidney injury (AKI). Medical records of adult (≥18 years) patients who underwent primary LT between 2004 and 2014 at a tertiary hospital were reviewed. Patients who required pretransplant renal replacement therapy and intraoperative piggyback technique were excluded. Patients were divided into 2 groups, VVB and non-VVB. AKI, determined by the Acute Kidney Injury Network criteria, was compared between the 2 groups. Propensity match was used to control selection bias that occurred before VVB and multivariable logistic regression was used to control confounding factors during and after VVB. Of 1037 adult patients who met the study inclusion criteria, 247 (23.8%) received VVB. A total of 442 patients (221 patients in each group) were matched. Aftermatch patients were further divided according to a predicted probability AKI model using preoperative creatinine (Cr), VVB, and intraoperative variables into 2 subgroups: normal and compromised pretransplant renal functions. In patients with compromised pretransplant renal function (Cr ≥1.2 mg/dL), the incidence of AKI was significantly lower in the VVB group compared with the non-VVB group (37.2% vs 50.8%; P = .033). VVB was an independent risk factor negatively associated with AKI (odds ratio, 0.1; 95% confidence interval, 0.1-0.4; P = .001). Renal replacement in 30 days and 1-year recipient mortality were not significantly different between the 2 groups. The incidence of posttransplant AKI was not significantly different between the 2 groups in patients with normal pretransplant renal function (Cr the role of intraoperative VVB in posttransplant AKI are warranted.
Fan, Kuangang; Zhang, Yan; Gao, Shujing; Wei, Xiang
2017-09-01
A class of SIR epidemic model with generalized nonlinear incidence rate is presented in this paper. Temporary immunity and stochastic perturbation are also considered. The existence and uniqueness of the global positive solution is achieved. Sufficient conditions guaranteeing the extinction and persistence of the epidemic disease are established. Moreover, the threshold behavior is discussed, and the threshold value R0 is obtained. We show that if R0 extinct with probability one, whereas if R0 > 1, then the system remains permanent in the mean.
Teng, Zhidong; Wang, Lei
2016-06-01
In this paper, a class of stochastic SIS epidemic models with nonlinear incidence rate is investigated. It is shown that the extinction and persistence of the disease in probability are determined by a threshold value R˜0. That is, if R˜0 1 then disease is weak permanent with probability one. To obtain the permanence in the mean of the disease, a new quantity R̂0 is introduced, and it is proved that if R̂0 > 1 the disease is permanent in the mean with probability one. Furthermore, the numerical simulations are presented to illustrate some open problems given in Remarks 1-3 and 5 of this paper.
Global asymptotic stability of a delayed SEIRS epidemic model with saturation incidence
International Nuclear Information System (INIS)
Zhang Tailei; Teng Zhidong
2008-01-01
In this paper, the asymptotic behavior of solutions of an autonomous SEIRS epidemic model with the saturation incidence is studied. Using the method of Liapunov-LaSalle invariance principle, we obtain the disease-free equilibrium is globally stable if the basic reproduction number is not greater than one. Moreover, we show that the disease is permanent if the basic reproduction number is greater than one. Furthermore, the sufficient conditions of locally and globally asymptotically stable convergence to an endemic equilibrium are obtained base on the permanence
Bertuzzo, E.; Mari, L.; Righetto, L.; Casagrandi, R.; Gatto, M.; Rodriguez-Iturbe, I.; Rinaldo, A.
2010-12-01
The seasonality of cholera and its relation with environmental drivers are receiving increasing interest and research efforts, yet they remain unsatisfactorily understood. A striking example is the observed annual cycle of cholera incidence in the Bengal region which exhibits two peaks despite the main environmental drivers that have been linked to the disease (air and sea surface temperature, zooplankton density, river discharge) follow a synchronous single-peak annual pattern. A first outbreak, mainly affecting the coastal regions, occurs in spring and it is followed, after a period of low incidence during summer, by a second, usually larger, peak in autumn also involving regions situated farther inland. A hydroclimatological explanation for this unique seasonal cycle has been recently proposed: the low river spring flows favor the intrusion of brackish water (the natural environment of the causative agent of the disease) which, in turn, triggers the first outbreak. The summer rising river discharges have a temporary dilution effect and prompt the repulsion of contaminated water which lowers the disease incidence. However, the monsoon flooding, together with the induced crowding of the population and the failure of the sanitation systems, can possibly facilitate the spatial transmission of the disease and promote the autumn outbreak. We test this hypothesis using a mechanistic, spatially explicit model of cholera epidemic. The framework directly accounts for the role of the river network in transporting and redistributing cholera bacteria among human communities as well as for the annual fluctuation of the river flow. The model is forced with the actual environmental drivers of the region, namely river flow and temperature. Our results show that these two drivers, both having a single peak in the summer, can generate a double peak cholera incidence pattern. Besides temporal patterns, the model is also able to qualitatively reproduce spatial patterns characterized
International Nuclear Information System (INIS)
Dreimann, Karsten; Linz, Stefan J.
2010-01-01
Graphical abstract: Deterministic surface pattern (left) and its stochastic counterpart (right) arising in a stochastic damped Kuramoto-Sivashinsky equation that serves as a model equation for ion-beam eroded surfaces and is systematically investigated. - Abstract: Using a recently proposed field equation for the surface evolution of ion-beam eroded semiconductor target materials under normal incidence, we systematically explore the impact of additive stochastic fluctuations that are permanently present during the erosion process. Specifically, we investigate the dependence of the surface roughness, the underlying pattern forming properties and the bifurcation behavior on the strength of the fluctuations.
Chaos induced by breakup of waves in a spatial epidemic model with nonlinear incidence rate
International Nuclear Information System (INIS)
Sun, Gui-Quan; Jin, Zhen; Liu, Quan-Xing; Li, Li
2008-01-01
Spatial epidemiology is the study of spatial variation in disease risk or incidence, including the spatial patterns of the population. The spread of diseases in human populations can exhibit large scale patterns, underlining the need for spatially explicit approaches. In this paper, the spatiotemporal complexity of a spatial epidemic model with nonlinear incidence rate, which includes the behavioral changes and crowding effect of the infective individuals, is investigated. Based on both theoretical analysis and computer simulations, we find out when, under the parameters which can guarantee a stable limit cycle in the non-spatial model, spiral and target waves can emerge. Moreover, two different kinds of breakup of waves are shown. Specifically, the breakup of spiral waves is from the core and the breakup of target waves is from the far-field, and both kinds of waves become irregular patterns at last. Our results reveal that the spatiotemporal chaos is induced by the breakup of waves. The results obtained confirm that diffusion can form spiral waves, target waves or spatial chaos of high population density, which enrich the findings of spatiotemporal dynamics in the epidemic model
The interaction evolution model of mass incidents with delay in a social network
Huo, Liang'an; Ma, Chenyang
2017-10-01
Recent years have witnessed rapid development of information technology. Today, modern media is widely used for the purpose of spreading information rapidly and widely. In particular, through micro-blog promotions, individuals tend to express their viewpoints and spread information on the internet, which could easily lead to public opinions. Moreover, government authorities also disseminate official information to guide public opinion and eliminate any incorrect conjecture. In this paper, a dynamical model with two delays is investigated to exhibit the interaction evolution between the public and official opinion fields in network mass incidents. Based on the theory of differential equations, the interaction mechanism between two public opinion fields in a micro-blog environment is analyzed. Two delays are proposed in the model to depict the response delays of public and official opinion fields. Some stable conditions are obtained, which shows that Hopf bifurcation can occur as delays cross critical values. Further, some numerical simulations are carried out to verify theoretical results. Our model indicates that there exists a golden time for government intervention, which should be emphasized given the impact of modern media and inaccurate rumors. If the government releases official information during the golden time, mass incidents on the internet can be controlled effectively.
Computational Modelling and Optimal Control of Ebola Virus Disease with non-Linear Incidence Rate
Takaidza, I.; Makinde, O. D.; Okosun, O. K.
2017-03-01
The 2014 Ebola outbreak in West Africa has exposed the need to connect modellers and those with relevant data as pivotal to better understanding of how the disease spreads and quantifying the effects of possible interventions. In this paper, we model and analyse the Ebola virus disease with non-linear incidence rate. The epidemic model created is used to describe how the Ebola virus could potentially evolve in a population. We perform an uncertainty analysis of the basic reproductive number R 0 to quantify its sensitivity to other disease-related parameters. We also analyse the sensitivity of the final epidemic size to the time control interventions (education, vaccination, quarantine and safe handling) and provide the cost effective combination of the interventions.
Prévot, Geoffroy; Hogan, Conor; Leoni, Thomas; Bernard, Romain; Moyen, Eric; Masson, Laurence
2016-12-30
We report a combined grazing incidence x-ray diffraction (GIXD), scanning tunneling microscopy (STM), and density-functional theory (DFT) study which clearly elucidates the atomic structure of the Si nanoribbons grown on the missing-row reconstructed Ag(110) surface. Our study allows us to discriminate between the theoretical models published in the literature, including the most stable atomic configurations and those based on a missing-row reconstructed Ag(110) surface. GIXD measurements unambiguously validate the pentamer model grown on the reconstructed surface, obtained from DFT. This pentamer atomistic model accurately matches the high-resolution STM images of the Si nanoribbons adsorbed on Ag(110). Our study closes the long-debated atomic structure of the Si nanoribbons grown on Ag(110) and definitively excludes a honeycomb structure similar to that of freestanding silicene.
Load function modelling for light impact
International Nuclear Information System (INIS)
Klingmueller, O.
1982-01-01
For Pile Integrity Testing light weight drop hammers are used to induce stress waves. In the computational analysis of one-dimensional wave propagation a load function has to be used. Several mechanical models and corresponding load functions are discussed. It is shown that a bell-shaped function which does not correspond to a mechanical model is in best accordance with test results and does not lead to numerical disturbances in the computational results. (orig.) [de
A Memristor Model with Piecewise Window Function
Directory of Open Access Journals (Sweden)
J. Yu
2013-12-01
Full Text Available In this paper, we present a memristor model with piecewise window function, which is continuously differentiable and consists of three nonlinear pieces. By introducing two parameters, the shape of this window function can be flexibly adjusted to model different types of memristors. Using this model, one can easily obtain an expression of memristance depending on charge, from which the numerical value of memristance can be readily calculated for any given charge, and eliminate the error occurring in the simulation of some existing window function models.
ONeill, S. M.; Larkin, N. K.; Martinez, M.; Rorig, M.; Solomon, R. C.; Dubowy, J.; Lahm, P. W.
2017-12-01
Specialists operationally deployed to wildfires to forecast expected smoke conditions for the public use many tools and information. These Air Resource Advisors (ARAs) are deployed as part of the Wildland Fire Air Quality Response Program (WFAQRP) and rely on smoke models, monitoring data, meteorological information, and satellite information to produce daily Smoke Outlooks for a region impacted by smoke from wildfires. These Smoke Outlooks are distributed to air quality and health agencies, published online via smoke blogs and other social media, and distributed by the Incident Public Information Officer (PIO), and ultimately to the public. Fundamental to these operations are smoke modeling systems such as the BlueSky Smoke Modeling Framework, which combines fire activity information, mapped fuel loadings, consumption and emissions models, and air quality/dispersion models such as HYSPLIT to produce predictions of PM2.5 concentrations downwind of wildland fires. Performance of this system at a variety of meteorological resolutions, fire initialization information, and vertical allocation of emissions is evaluated for the Summer of 2015 when over 400,000 hectares burned in the northwestern US state of Washington and 1-hr average fine particulate matter (PM2.5) concentrations exceeded 700 μg/m3. The performance of the system at the 12-km, 4-km, and 1.33-km resolutions is evaluated using 1-hr average PM2.5 measurements from permanent monitors and temporary monitors deployed specifically for wildfires by ARAs on wildfire incident command teams. At the higher meteorological resolution (1.33-km) the terrain features are more detailed, showing better valley structures and in general, PM2.5 concentrations were greater in the valleys with the 1.33-km meteorological domain than with the 4-km domain.
International Nuclear Information System (INIS)
Salehi, M.; Mohammad, K.; Frahani, Mahmud M.; Zeraati, H.; Nourijelyani, K.; Zayeri, F.
2008-01-01
Objective was to identify the effect of environmental factors on malariarisk and to visualize spatial map of malaria standard incidence rates inSistan and Baluchistan province, Islamic Republic of Iran. In thiscross-sectional study, the data from 42, 162 registered new malaria casesfrom 21 March 2001 (Iran new year) to 21 of March 2006 were studied. Todescribe the statistical association between environmental factors andmalaria risk, a generalized linear mixed model approach was utilized. Inaddition, we used the second ordered stationary Kriging and a variogram todetermine the appropriate spatial correlation structure among the malariastandard incidence rates, and provide a proper malaria risk map in the areaunder study. The obtained results from the spatial modeling revealed thathumidity (p=0.0004), temperature (p<0.0001) and elevation (p<0.0001) werepositively, and precipitation (p=0.0029) was inversely correlated with themalaria risk. Moreover, the malaria risk amp based on the predicted valuesshowed that the south part of this province (Baluchistan) has a higher riskof malaria, compared to the northern area (Sistan). Since the effectiveenvironmental factors on malaria risk are out of human's control, the healthpolicy makers in this province should pay more attention to the areas withhigher temperature, elevation and humidity, as well as, low rainfalldistricts. (author)
The oil spill modelling in the Sea of Japan: application to the tanker 'Nakhodka' 1997 incident
International Nuclear Information System (INIS)
Varlamov, S.M.; Yoon, J.-H.; Hirose, N.; Kawamura, H.
1998-01-01
In January 1997 the Russian tanker 'NAKHODKA' spilled into the Sea of Japan about 5000 tons of heavy fuel oil type C. Most of it reached the coast of Japan and damaged the environment. This incident forced the development of the operational system for the prediction of oil spills in the Sea of Japan. As a part of this system the model for oil spill modelling is presented. The modelled climatological sea currents were used in these simulators, generated by the three-dimensional primitive ocean circulation model with 10-minute horizontal resolution and 19 vertical levels. The model was forced by climatological atmospheric winds and heat fluxes. The wind currents in the upper sea layer were estimated by the wind data of ECMWF with 6 hours time and 0.5625-degree spatial resolution. The vertical structure of the total currents was interpolated using both wind driven currents and the climatological model currents data at the model levels. The oil spill was modelled with the particle tracking techniques. The model included the advection by currents, random diffusion, the buoyancy effect and the parameterisation of oil evaporation, biodegradation and beaching. For the deep sea the parameterisation of diffusion depends from the stratification, taken from the ocean circulation model output. The results demonstrated the defined relation with the observed propagation of the oil along the coast of Japan and highlighted the most important directions for the model development. The main is the realisation of the model for the real-time simulations and forecasts of the ocean currents with the fine resolution in the upper layer of the Sea of Japan. (author)
The Swiss cheese model of safety incidents: are there holes in the metaphor?
Directory of Open Access Journals (Sweden)
Perneger Thomas V
2005-11-01
Full Text Available Abstract Background Reason's Swiss cheese model has become the dominant paradigm for analysing medical errors and patient safety incidents. The aim of this study was to determine if the components of the model are understood in the same way by quality and safety professionals. Methods Survey of a volunteer sample of persons who claimed familiarity with the model, recruited at a conference on quality in health care, and on the internet through quality-related websites. The questionnaire proposed several interpretations of components of the Swiss cheese model: a slice of cheese, b hole, c arrow, d active error, e how to make the system safer. Eleven interpretations were compatible with this author's interpretation of the model, 12 were not. Results Eighty five respondents stated that they were very or quite familiar with the model. They gave on average 15.3 (SD 2.3, range 10 to 21 "correct" answers out of 23 (66.5% – significantly more than 11.5 "correct" answers that would expected by chance (p Conclusion The interpretations of specific features of the Swiss cheese model varied considerably among quality and safety professionals. Reaching consensus about concepts of patient safety requires further work.
Model wave functions for the deuteron
International Nuclear Information System (INIS)
Certov, A.; Mathelitsch, L.; Moravcsik, M.J.
1987-01-01
Model wave functions are constructed for the deuteron to facilitate the unambiguous exploration of dependencies on the percentage D state and on the small-, medium-, and large-distance parts of the deuteron wave function. The wave functions are constrained by those deuteron properties which are accurately known experimentally, and are in an analytic form which is easily integrable in expressions usually encountered in the use of such wave functions
Vilà de Muga, M; Serrano Llop, A; Rifé Escudero, E; Jabalera Contreras, M; Luaces Cubells, C
2015-10-01
The aim of this study is to analyse changes in the incidents reported after the implementation of a new model, and study its results on patient safety. In 2012 an observational study with prospective collection of incidents reported between 2007 and 2011 was conducted. In May 2012 a model change was made in order to increase the number of reports, analyse their causes, and improve the feedback to the service. Professional safety representatives were assigned to every department, information and diffusion sessions were held, and a new incident reporting system was implemented. With the new model, a new observational study with prospective collection of the reports during one year was initiated, and the results compared between models. In 2011, only 19 incidents were reported in the Emergency Department, and between June 1, 2012 to June 1, 2013, 106 incidents (5.6 times more). The incidents reported were medication incidents (57%), identification (26%), and procedures (7%). The most frequent causes were human (70.7%), lack of training (22.6%), and working conditions (15.1%). Some measures were implemented as a result of these incidents: a surgical checklist, unit doses of salbutamol, tables of weight-standardised doses of drugs for cardiopulmonary resuscitation. The new model of reporting incidents has enhanced the reports and has allowed improvements and the implementation of preventive measures, increasing the patient safety in the Emergency Department. Copyright © 2014 Asociación Española de Pediatría. Published by Elsevier España, S.L.U. All rights reserved.
Barrios, J. M.; Verstraeten, W. W.; Farifteh, J.; Maes, P.; Aerts, J. M.; Coppin, P.
2012-04-01
Lyme borreliosis (LB) is the most common tick-borne disease in Europe and incidence growth has been reported in several European countries during the last decade. LB is caused by the bacterium Borrelia burgdorferi and the main vector of this pathogen in Europe is the tick Ixodes ricinus. LB incidence and spatial spread is greatly dependent on environmental conditions impacting habitat, demography and trophic interactions of ticks and the wide range of organisms ticks parasite. The landscape configuration is also a major determinant of tick habitat conditions and -very important- of the fashion and intensity of human interaction with vegetated areas, i.e. human exposure to the pathogen. Hence, spatial notions as distance and adjacency between urban and vegetated environments are related to human exposure to tick bites and, thus, to risk. This work tested the adequacy of a gravity model setting to model the observed spatio-temporal pattern of LB as a function of location and size of urban and vegetated areas and the seasonal and annual change in the vegetation dynamics as expressed by MODIS NDVI. Opting for this approach implies an analogy with Newton's law of universal gravitation in which the attraction forces between two bodies are directly proportional to the bodies mass and inversely proportional to distance. Similar implementations have proven useful in fields like trade modeling, health care service planning, disease mapping among other. In our implementation, the size of human settlements and vegetated systems and the distance separating these landscape elements are considered the 'bodies'; and the 'attraction' between them is an indicator of exposure to pathogen. A novel element of this implementation is the incorporation of NDVI to account for the seasonal and annual variation in risk. The importance of incorporating this indicator of vegetation activity resides in the fact that alterations of LB incidence pattern observed the last decade have been ascribed
Liu, L; Luan, R S; Yin, F; Zhu, X P; Lü, Q
2016-01-01
Hand, foot and mouth disease (HFMD) is an infectious disease caused by enteroviruses, which usually occurs in children aged ARIMA) model to forecast HFMD incidence in Sichuan province, China. HFMD infection data from January 2010 to June 2014 were used to fit the ARIMA model. The coefficient of determination (R 2), normalized Bayesian Information Criterion (BIC) and mean absolute percentage of error (MAPE) were used to evaluate the goodness-of-fit of the constructed models. The fitted ARIMA model was applied to forecast the incidence of HMFD from April to June 2014. The goodness-of-fit test generated the optimum general multiplicative seasonal ARIMA (1,0,1) × (0,1,0)12 model (R 2 = 0·692, MAPE = 15·982, BIC = 5·265), which also showed non-significant autocorrelations in the residuals of the model (P = 0·893). The forecast incidence values of the ARIMA (1,0,1) × (0,1,0)12 model from July to December 2014 were 4103-9987, which were proximate forecasts. The ARIMA model could be applied to forecast HMFD incidence trend and provide support for HMFD prevention and control. Further observations should be carried out continually into the time sequence, and the parameters of the models could be adjusted because HMFD incidence will not be absolutely stationary in the future.
Miglioretti, Diana L; Lange, Jane; van den Broek, Jeroen J; Lee, Christoph I; van Ravesteyn, Nicolien T; Ritley, Dominique; Kerlikowske, Karla; Fenton, Joshua J; Melnikow, Joy; de Koning, Harry J; Hubbard, Rebecca A
2016-02-16
Estimates of risk for radiation-induced breast cancer from mammography screening have not considered variation in dose exposure or diagnostic work-up after abnormal screening results. To estimate distributions of radiation-induced breast cancer incidence and mortality from digital mammography screening while considering exposure from screening and diagnostic mammography and dose variation among women. 2 simulation-modeling approaches. U.S. population. Women aged 40 to 74 years. Annual or biennial digital mammography screening from age 40, 45, or 50 years until age 74 years. Lifetime breast cancer deaths averted (benefits) and radiation-induced breast cancer incidence and mortality (harms) per 100,000 women screened. Annual screening of 100,000 women aged 40 to 74 years was projected to induce 125 breast cancer cases (95% CI, 88 to 178) leading to 16 deaths (CI, 11 to 23), relative to 968 breast cancer deaths averted by early detection from screening. Women exposed at the 95th percentile were projected to develop 246 cases of radiation-induced breast cancer leading to 32 deaths per 100,000 women. Women with large breasts requiring extra views for complete examination (8% of population) were projected to have greater radiation-induced breast cancer risk (266 cancer cases and 35 deaths per 100,000 women) than other women (113 cancer cases and 15 deaths per 100,000 women). Biennial screening starting at age 50 years reduced risk for radiation-induced cancer 5-fold. Life-years lost from radiation-induced breast cancer could not be estimated. Radiation-induced breast cancer incidence and mortality from digital mammography screening are affected by dose variability from screening, resultant diagnostic work-up, initiation age, and screening frequency. Women with large breasts may have a greater risk for radiation-induced breast cancer. Agency for Healthcare Research and Quality, U.S. Preventive Services Task Force, National Cancer Institute.
International Nuclear Information System (INIS)
Peterson, L.E.; Cucinotta, F.A.
1999-01-01
Estimating uncertainty in lifetime cancer risk for human exposure to space radiation is a unique challenge. Conventional risk assessment with low-linear-energy-transfer (LET)-based risk from Japanese atomic bomb survivor studies may be inappropriate for relativistic protons and nuclei in space due to track structure effects. This paper develops a Monte Carlo mixture model (MCMM) for transferring additive, National Institutes of Health multiplicative, and multiplicative excess cancer incidence risks based on Japanese atomic bomb survivor data to determine excess incidence risk for various US astronaut exposure profiles. The MCMM serves as an anchor point for future risk projection methods involving biophysical models of DNA damage from space radiation. Lifetime incidence risks of radiation-induced cancer for the MCMM based on low-LET Japanese data for nonleukemia (all cancers except leukemia) were 2.77 (90% confidence limit, 0.75-11.34) for males exposed to 1 Sv at age 45 and 2.20 (90% confidence limit, 0.59-10.12) for males exposed at age 55. For females, mixture model risks for nonleukemia exposed separately to 1 Sv at ages of 45 and 55 were 2.98 (90% confidence limit, 0.90-11.70) and 2.44 (90% confidence limit, 0.70-10.30), respectively. Risks for high-LET 200 MeV protons (LET=0.45 keV/μm), 1 MeV α-particles (LET=100 keV/μm), and 600 MeV iron particles (LET=180 keV/μm) were scored on a per particle basis by determining the particle fluence required for an average of one particle per cell nucleus of area 100 μm 2 . Lifetime risk per proton was 2.68x10 -2 % (90% confidence limit, 0.79x10 -3 %-0.514x10 -2 %). For α-particles, lifetime risk was 14.2% (90% confidence limit, 2.5%-31.2%). Conversely, lifetime risk per iron particle was 23.7% (90% confidence limit, 4.5%-53.0%). Uncertainty in the DDREF for high-LET particles may be less than that for low-LET radiation because typically there is very little dose-rate dependence. Probability density functions for
Bonnie, F.; Arnold, M. D.; Smith, G. B.; Gentle, A. R.
2013-09-01
The optical resonances that occur in nanostructured metal layers are modulated in thin film stacks if the nanostructured layer is separated from a reflecting conducting layer by various thicknesses of thin dielectric. We have measured and modeled the optical response of interacting silver layers, with alumina spacer thickness ranging from a few nm to 50 nm, for s- and p-polarized incident light, and a range of incident angles. Standard thin film models, including standard effective medium models for the nanostructured layer, will break down for spacer thickness below a critical threshold. For example, with polarisation in the film plane and some nano-islands, it may occur at around 10 nm depending on spacer refractive index. Of particular interest here are novel effects observed with the onset of percolation in the nanolayer. Hot spot effects can be modified by nearby mirrors. Other modes to consider include (a) a two-particle mode involving a particle and its mirror image (b) A Fano resonance from hybridisation of localized and de-localised plasmon modes (c) a Babinet's core-(partial) shell particle with metal core-dielectric shell in metal (d) spacing dependent phase modulation (e) the impact of field gradients induced by the mirror at the nano-layer.
Mathematical modeling of zika virus disease with nonlinear incidence and optimal control
Goswami, Naba Kumar; Srivastav, Akhil Kumar; Ghosh, Mini; Shanmukha, B.
2018-04-01
The Zika virus was first discovered in a rhesus monkey in the Zika Forest of Uganda in 1947, and it was isolated from humans in Nigeria in 1952. Zika virus disease is primarily a mosquito-borne disease, which is transmitted to human primarily through the bite of an infected Aedes species mosquito. However, there is documented evidence of sexual transmission of this disease too. In this paper, a nonlinear mathematical model for Zika virus by considering nonlinear incidence is formulated and analyzed. The equilibria and the basic reproduction number (R0) of the model are found. The stability of the different equilibria of the model is discussed in detail. When the basic reproduction number R0 1, we have endemic equilibrium which is locally stable under some restriction on parameters. Further this model is extended to optimal control model and is analyzed by using Pontryagin’s Maximum Principle. It has been observed that optimal control plays a significant role in reducing the number of zika infectives. Finally, numerical simulation is performed to illustrate the analytical findings.
Lordan, Sinéad; Ross, R. Paul; Stanton, Catherine
2011-01-01
The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases. PMID:21747748
Directory of Open Access Journals (Sweden)
Catherine Stanton
2011-06-01
Full Text Available The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases.
Diagnostics for Linear Models With Functional Responses
Xu, Hongquan; Shen, Qing
2005-01-01
Linear models where the response is a function and the predictors are vectors are useful in analyzing data from designed experiments and other situations with functional observations. Residual analysis and diagnostics are considered for such models. Studentized residuals are defined and their properties are studied. Chi-square quantile-quantile plots are proposed to check the assumption of Gaussian error process and outliers. Jackknife residuals and an associated test are proposed to det...
Functional Modeling of Neural-Glia Interaction
DEFF Research Database (Denmark)
Postnov, D.E.; Brazhe, N.A.; Sosnovtseva, Olga
2012-01-01
Functional modeling is an approach that focuses on the representation of the qualitative dynamics of the individual components (e.g. cells) of a system and on the structure of the interaction network.......Functional modeling is an approach that focuses on the representation of the qualitative dynamics of the individual components (e.g. cells) of a system and on the structure of the interaction network....
Neural modeling of prefrontal executive function
Energy Technology Data Exchange (ETDEWEB)
Levine, D.S. [Univ. of Texas, Arlington, TX (United States)
1996-12-31
Brain executive function is based in a distributed system whereby prefrontal cortex is interconnected with other cortical. and subcortical loci. Executive function is divided roughly into three interacting parts: affective guidance of responses; linkage among working memory representations; and forming complex behavioral schemata. Neural network models of each of these parts are reviewed and fit into a preliminary theoretical framework.
Yu, Bing; Li, Alexander H; Muzny, Donna; Veeraraghavan, Narayanan; de Vries, Paul S; Bis, Joshua C; Musani, Solomon K; Alexander, Danny; Morrison, Alanna C; Franco, Oscar H; Uitterlinden, André; Hofman, Albert; Dehghan, Abbas; Wilson, James G; Psaty, Bruce M; Gibbs, Richard; Wei, Peng; Boerwinkle, Eric
2015-04-01
Histidine is a semiessential amino acid with antioxidant and anti-inflammatory properties. Few data are available on the associations between genetic variants, histidine levels, and incident coronary heart disease (CHD) in a population-based sample. By conducting whole exome sequencing on 1152 African Americans in the Atherosclerosis Risk in Communities (ARIC) study and focusing on loss-of-function (LoF) variants, we identified 3 novel rare LoF variants in HAL, a gene that encodes histidine ammonia-lyase in the first step of histidine catabolism. These LoF variants had large effects on blood histidine levels (β=0.26; P=1.2×10(-13)). The positive association with histidine levels was replicated by genotyping an independent sample of 718 ARIC African Americans (minor allele frequency=1%; P=1.2×10(-4)). In addition, high blood histidine levels were associated with reduced risk of developing incident CHD with an average of 21.5 years of follow-up among African Americans (hazard ratio=0.18; P=1.9×10(-4)). This finding was validated in an independent sample of European Americans from the Framingham Heart Study (FHS) Offspring Cohort. However, LoF variants in HAL were not directly significantly associated with incident CHD after meta-analyzing results from the CHARGE Consortium. Three LoF mutations in HAL were associated with increased histidine levels, which in turn were shown to be inversely related to the risk of CHD among both African Americans and European Americans. Future investigations on the association between HAL gene variation and CHD are warranted. © 2015 American Heart Association, Inc.
Elevated incidence of dental caries in a mouse model of cystic fibrosis.
Directory of Open Access Journals (Sweden)
Marcelo A Catalán
2011-01-01
Full Text Available Dental caries is the single most prevalent and costly infectious disease worldwide, affecting more than 90% of the population in the U.S. The development of dental cavities requires the colonization of the tooth surface by acid-producing bacteria, such as Streptococcus mutans. Saliva bicarbonate constitutes the main buffering system which neutralizes the pH fall generated by the plaque bacteria during sugar metabolism. We found that the saliva pH is severely decreased in a mouse model of cystic fibrosis disease (CF. Given the close relationship between pH and caries development, we hypothesized that caries incidence might be elevated in the mouse CF model.We induced carious lesions in CF and wildtype mice by infecting their oral cavity with S. mutans, a well-studied cariogenic bacterium. After infection, the mice were fed a high-sucrose diet for 5 weeks (diet 2000. The mice were then euthanized and their jaws removed for caries scoring and bacterial counting. A dramatic increase in caries and severity of lesions scores were apparent in CF mice compared to their wildtype littermates. The elevated incidence of carious lesions correlated with a striking increase in the S. mutans viable population in dental plaque (20-fold increase in CF vs. wildtype mice; p value < 0.003; t test. We also found that the pilocarpine-stimulated saliva bicarbonate concentration was significantly reduced in CF mice (16 ± 2 mM vs. 31 ± 2 mM, CF and wildtype mice, respectively; p value < 0.01; t test.Considering that bicarbonate is the most important pH buffering system in saliva, and the adherence and survival of aciduric bacteria such as S. mutans are enhanced at low pH values, we speculate that the decrease in the bicarbonate content and pH buffering of the saliva is at least partially responsible for the increased severity of lesions observed in the CF mouse.
International Nuclear Information System (INIS)
Francois, P.
1996-01-01
We undertook a study programme at the end of 1991. To start with, we performed some exploratory studies aimed at learning some preliminary lessons on this type of analysis: Assessment of the interest of probabilistic incident analysis; possibility of using PSA scenarios; skills and resources required. At the same time, EPN created a working group whose assignment was to define a new approach for analysis of incidents on NPPs. This working group gave thought to both aspects of Operating Feedback that EPN wished to improve: Analysis of significant incidents; analysis of potential consequences. We took part in the work of this group, and for the second aspects, we proposed a method based on an adaptation of the event-tree method in order to establish a link between existing PSA models and actual incidents. Since PSA provides an exhaustive database of accident scenarios applicable to the two most common types of units in France, they are obviously of interest for this sort of analysis. With this method we performed some incident analyses, and at the same time explores some methods employed abroad, particularly ASP (Accident Sequence Precursor, a method used by the NRC). Early in 1994 EDF began a systematic analysis programme. The first, transient phase will set up methods and an organizational structure. 7 figs
Energy Technology Data Exchange (ETDEWEB)
Francois, P
1997-12-31
We undertook a study programme at the end of 1991. To start with, we performed some exploratory studies aimed at learning some preliminary lessons on this type of analysis: Assessment of the interest of probabilistic incident analysis; possibility of using PSA scenarios; skills and resources required. At the same time, EPN created a working group whose assignment was to define a new approach for analysis of incidents on NPPs. This working group gave thought to both aspects of Operating Feedback that EPN wished to improve: Analysis of significant incidents; analysis of potential consequences. We took part in the work of this group, and for the second aspects, we proposed a method based on an adaptation of the event-tree method in order to establish a link between existing PSA models and actual incidents. Since PSA provides an exhaustive database of accident scenarios applicable to the two most common types of units in France, they are obviously of interest for this sort of analysis. With this method we performed some incident analyses, and at the same time explores some methods employed abroad, particularly ASP (Accident Sequence Precursor, a method used by the NRC). Early in 1994 EDF began a systematic analysis programme. The first, transient phase will set up methods and an organizational structure. 7 figs.
A Multivariate Approach to Functional Neuro Modeling
DEFF Research Database (Denmark)
Mørch, Niels J.S.
1998-01-01
by the application of linear and more flexible, nonlinear microscopic regression models to a real-world dataset. The dependency of model performance, as quantified by generalization error, on model flexibility and training set size is demonstrated, leading to the important realization that no uniformly optimal model......, provides the basis for a generalization theoretical framework relating model performance to model complexity and dataset size. Briefly summarized the major topics discussed in the thesis include: - An introduction of the representation of functional datasets by pairs of neuronal activity patterns...... exists. - Model visualization and interpretation techniques. The simplicity of this task for linear models contrasts the difficulties involved when dealing with nonlinear models. Finally, a visualization technique for nonlinear models is proposed. A single observation emerges from the thesis...
The universal function in color dipole model
Jalilian, Z.; Boroun, G. R.
2017-10-01
In this work we review color dipole model and recall properties of the saturation and geometrical scaling in this model. Our primary aim is determining the exact universal function in terms of the introduced scaling variable in different distance than the saturation radius. With inserting the mass in calculation we compute numerically the contribution of heavy productions in small x from the total structure function by the fraction of universal functions and show the geometrical scaling is established due to our scaling variable in this study.
Prediction of Chemical Function: Model Development and ...
The United States Environmental Protection Agency’s Exposure Forecaster (ExpoCast) project is developing both statistical and mechanism-based computational models for predicting exposures to thousands of chemicals, including those in consumer products. The high-throughput (HT) screening-level exposures developed under ExpoCast can be combined with HT screening (HTS) bioactivity data for the risk-based prioritization of chemicals for further evaluation. The functional role (e.g. solvent, plasticizer, fragrance) that a chemical performs can drive both the types of products in which it is found and the concentration in which it is present and therefore impacting exposure potential. However, critical chemical use information (including functional role) is lacking for the majority of commercial chemicals for which exposure estimates are needed. A suite of machine-learning based models for classifying chemicals in terms of their likely functional roles in products based on structure were developed. This effort required collection, curation, and harmonization of publically-available data sources of chemical functional use information from government and industry bodies. Physicochemical and structure descriptor data were generated for chemicals with function data. Machine-learning classifier models for function were then built in a cross-validated manner from the descriptor/function data using the method of random forests. The models were applied to: 1) predict chemi
Directory of Open Access Journals (Sweden)
R.V. Tkach
2016-08-01
Full Text Available Today, the violations of the digestive system in children of the first years of life remain the actual problem of practical pediatrics and are the common cause for parents to visit a doctor. The importance in the genesis of functional disorders of the digestive system in children of this age may belongs to lactase deficiency. 327 children from Lviv were included in the questionnaire survey. The aim of the study was to evaluate the incidence of clinical symptoms that may be associated with lactase deficiency in infants. Among the clinical symptoms in young children, according to the survey, regurgitation and colic, stool disorders dominated. The diagnosis of lactase deficiency was established in 3.4 % (11 of children, 2.8 % (9 children received enzyme of lactase.
Sjolund, Jessica; Garcia Anton, Desiree; Bayes, Liz Y; Hoekstra, Tiny; Dekker, Friedo W; Munoz Mendoza, Jair
2016-09-01
The effect of diuretics on residual renal function expressed as residual GFR (rGFR) and urine volume (rUV) using 24-hour urine collections has not been well examined in hemodialysis (HD) patients. We present a small (seven patient) but provocative case series describing a strikingly low rate of decline in rUV and rGFR (average of creatinine and urea clearances, 24-hour urine collections) in patients treated with increasing doses of furosemide (up to 360 mg/day) during the first 2 years after initiation of HD. Between 6 and 12 months, the mean rUV fell by 1 ml/month, whereas rGFR declined by 0.03 ml/min/1.73 m(2) /month. The mean rate of decline from 12 to 24 months for rUV (33 ml/month) and rGFR (0.02 ml/min/1.73 m(2) /month) were also low. While data are clearly limited and the observation retrospective, they are consistent with the better documented benefit of diuretics observed in end-stage renal disease patients treated with peritoneal dialysis. © 2016 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Artur Badyda
2016-11-01
Full Text Available It is essential in pulmonary disease research to take into account traffic-related air pollutant exposure among urban inhabitants. In our study, 4985 people were examined for spirometric parameters in the presented research which was conducted in the years 2008–2012. The research group was divided into urban and rural residents. Traffic density, traffic structure and velocity, as well as concentrations of selected air pollutants (CO, NO2 and PM10 were measured at selected areas. Among people who live in the city, lower percentages of predicted values of spirometric parameters were noticed in comparison to residents of rural areas. Taking into account that the difference in the five-year mean concentration of PM10 in the considered city and rural areas was over 17 μg/m3, each increase of PM10 by 10 μg/m3 is associated with the decline in FEV1 (forced expiratory volume during the first second of expiration by 1.68%. These findings demonstrate that traffic-related air pollutants may have a significant influence on the decline of pulmonary function and the growing rate of respiratory diseases.
Functional model of biological neural networks.
Lo, James Ting-Ho
2010-12-01
A functional model of biological neural networks, called temporal hierarchical probabilistic associative memory (THPAM), is proposed in this paper. THPAM comprises functional models of dendritic trees for encoding inputs to neurons, a first type of neuron for generating spike trains, a second type of neuron for generating graded signals to modulate neurons of the first type, supervised and unsupervised Hebbian learning mechanisms for easy learning and retrieving, an arrangement of dendritic trees for maximizing generalization, hardwiring for rotation-translation-scaling invariance, and feedback connections with different delay durations for neurons to make full use of present and past informations generated by neurons in the same and higher layers. These functional models and their processing operations have many functions of biological neural networks that have not been achieved by other models in the open literature and provide logically coherent answers to many long-standing neuroscientific questions. However, biological justifications of these functional models and their processing operations are required for THPAM to qualify as a macroscopic model (or low-order approximate) of biological neural networks.
Mathematical modeling and visualization of functional neuroimages
DEFF Research Database (Denmark)
Rasmussen, Peter Mondrup
This dissertation presents research results regarding mathematical modeling in the context of the analysis of functional neuroimages. Specifically, the research focuses on pattern-based analysis methods that recently have become popular analysis tools within the neuroimaging community. Such methods...... neuroimaging data sets are characterized by relatively few data observations in a high dimensional space. The process of building models in such data sets often requires strong regularization. Often, the degree of model regularization is chosen in order to maximize prediction accuracy. We focus on the relative...... be carefully selected, so that the model and its visualization enhance our ability to interpret brain function. The second part concerns interpretation of nonlinear models and procedures for extraction of ‘brain maps’ from nonlinear kernel models. We assess the performance of the sensitivity map as means...
Structure functions in the chiral bag model
International Nuclear Information System (INIS)
Sanjose, V.; Vento, V.; Centro Mixto CSIC/Valencia Univ., Valencia
1989-01-01
We calculate the structure functions of an isoscalar nuclear target for the deep inelastic scattering by leptons in an extended version of the chiral bag model which incorporates the qanti q structure of the pions in the cloud. Bjorken scaling and Regge behavior are satisfied. The model calculation reproduces the low-x behavior of the data but fails to explain the medium- to large-x behavior. Evolution of the quark structure functions seem inevitable to attempt a connection between the low-energy models and the high-energy behavior of quantum chromodynamics. (orig.)
Structure functions in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Sanjose, V.; Vento, V.
1989-07-13
We calculate the structure functions of an isoscalar nuclear target for the deep inelastic scattering by leptons in an extended version of the chiral bag model which incorporates the qanti q structure of the pions in the cloud. Bjorken scaling and Regge behavior are satisfied. The model calculation reproduces the low-x behavior of the data but fails to explain the medium- to large-x behavior. Evolution of the quark structure functions seem inevitable to attempt a connection between the low-energy models and the high-energy behavior of quantum chromodynamics. (orig.).
Directory of Open Access Journals (Sweden)
Edlund Stefan
2012-09-01
Full Text Available Abstract Background The role of the Anopheles vector in malaria transmission and the effect of climate on Anopheles populations are well established. Models of the impact of climate change on the global malaria burden now have access to high-resolution climate data, but malaria surveillance data tends to be less precise, making model calibration problematic. Measurement of malaria response to fluctuations in climate variables offers a way to address these difficulties. Given the demonstrated sensitivity of malaria transmission to vector capacity, this work tests response functions to fluctuations in land surface temperature and precipitation. Methods This study of regional sensitivity of malaria incidence to year-to-year climate variations used an extended Macdonald Ross compartmental disease model (to compute malaria incidence built on top of a global Anopheles vector capacity model (based on 10 years of satellite climate data. The predicted incidence was compared with estimates from the World Health Organization and the Malaria Atlas. The models and denominator data used are freely available through the Eclipse Foundation’s Spatiotemporal Epidemiological Modeller (STEM. Results Although the absolute scale factor relating reported malaria to absolute incidence is uncertain, there is a positive correlation between predicted and reported year-to-year variation in malaria burden with an averaged root mean square (RMS error of 25% comparing normalized incidence across 86 countries. Based on this, the proposed measure of sensitivity of malaria to variations in climate variables indicates locations where malaria is most likely to increase or decrease in response to specific climate factors. Bootstrapping measures the increased uncertainty in predicting malaria sensitivity when reporting is restricted to national level and an annual basis. Results indicate a potential 20x improvement in accuracy if data were available at the level ISO 3166–2
The SOS model partition function and the elliptic weight functions
International Nuclear Information System (INIS)
Pakuliak, S; Silantyev, A; Rubtsov, V
2008-01-01
We generalized a recent observation (Khoroshkin and Pakuliak 2005 Theor. Math. Phys. 145 1373) that the partition function of the six-vertex model with domain wall boundary conditions can be obtained from a calculation of projections of the product of total currents in the quantum affine algebra U q (sl 2 -hat) in its current realization. A generalization is done for the elliptic current algebra (Enriquez and Felder 1998 Commun. Math. Phys. 195 651, Enriquez and Rubtsov 1997 Ann. Sci. Ecole Norm. Sup. 30 821). The projections of the product of total currents in this case are calculated explicitly and are presented as integral transforms of a product of the total currents. It is proved that the integral kernel of this transform is proportional to the partition function of the SOS model with domain wall boundary conditions
Directory of Open Access Journals (Sweden)
Ina Bähr
2017-01-01
Full Text Available Obesity is associated with an increased colon cancer incidence, but underlying mechanisms remained unclear. Previous studies showed altered Natural killer (NK cell functions in obese individuals. Therefore, we studied the impact of an impaired NK cell functionality on the increased colon cancer risk in obesity. In vitro investigations demonstrated a decreased IFN-γ secretion and cytotoxicity of human NK cells against colon tumor cells after NK cell preincubation with the adipokine leptin. In addition, leptin incubation decreased the expression of activating NK cell receptors. In animal studies, colon cancer growth was induced by injection of azoxymethane (AOM in normal weight and diet-induced obese rats. Body weight and visceral fat mass were increased in obese animals compared to normal weight rats. AOM-treated obese rats showed an increased quantity, size, and weight of colon tumors compared to the normal weight tumor group. Immunohistochemical analyses demonstrated a decreased number of NK cells in spleen and liver in obesity. Additionally, the expression levels of activating NK cell receptors were lower in spleen and liver of obese rats. The results show for the first time that the decreased number and impaired NK cell function may be one cause for the higher colon cancer risk in obesity.
Simulation model of lung cancer incidence related to smoking and radon daughter exposure
International Nuclear Information System (INIS)
Stolowijk, J.A.J.
1990-01-01
A mathematical model of lung cancer and radon daughter exposure is presented. It is aimed to provide a quantitative estimate in the form of dose-effect relationship. The nature of the cigarette smoking and radon exposure interaction it is shown to be a multiplicative or sub-multiplicative function rather than a simpler model in which the effect of the two exposures would be summed. The model was written in the SAS programming language. An annotated listing of the program is given. 4 refs
Data Acquisition for Quality Loss Function Modelling
DEFF Research Database (Denmark)
Pedersen, Søren Nygaard; Howard, Thomas J.
2016-01-01
Quality loss functions can be a valuable tool when assessing the impact of variation on product quality. Typically, the input for the quality loss function would be a measure of the varying product performance and the output would be a measure of quality. While the unit of the input is given by t...... by the product function in focus, the quality output can be measured and quantified in a number of ways. In this article a structured approach for acquiring stakeholder satisfaction data for use in quality loss function modelling is introduced.......Quality loss functions can be a valuable tool when assessing the impact of variation on product quality. Typically, the input for the quality loss function would be a measure of the varying product performance and the output would be a measure of quality. While the unit of the input is given...
Directory of Open Access Journals (Sweden)
Yulia G. Krasnozhon
2018-03-01
Full Text Available Modern information technologies have an increasing importance for development dynamics and management structure of an enterprise. The management efficiency of implementation of modern information technologies directly related to the quality of information security incident management. However, issues of assessment of the impact of information security incidents management on quality and efficiency of the enterprise management system are not sufficiently highlighted neither in Russian nor in foreign literature. The main direction to approach these problems is the optimization of the process automation system of the information security incident management. Today a special attention is paid to IT-technologies while dealing with information security incidents at mission-critical facilities in Russian Federation such as the Federal Tax Service of Russia (FTS. It is proposed to use the mathematical apparatus of queueing theory in order to build a mathematical model of the system optimization. The developed model allows to estimate quality of the management taking into account the rules and restrictions imposed on the system by the effects of information security incidents. Here an example is given in order to demonstrate the system in work. The obtained statistical data are shown. An implementation of the system discussed here will improve the quality of the Russian FTS services and make responses to information security incidents faster.
International Nuclear Information System (INIS)
Toeroek, Szabolcs; Borgulya, Gabor; Lobmayer, Peter; Jakab, Zsuzsanna; Schuler, Dezsoe; Fekete, Gyoergy
2005-01-01
The incidence of childhood leukaemia in Hungary has yet to be reported, although data are available since the early 70s. The Hungarian data therefore cover the time before and after the Chernobyl nuclear accident (1986). The aim of this study was to assess the effects of the Chernobyl accident on childhood leukaemia incidence in Hungary. A population-based study was carried out using data of the National Paediatric Cancer Registry of Hungary from 1973 to 2002. The total number of cases was 2204. To test the effect of the Chernobyl accident the authors applied a new approach called 'Hypothesized Impact Period Interpolation'-model, which takes into account the increasing trend of childhood leukaemia incidence and the hypothesized exposure and latency times. The incidence of leukaemia in the age group 0-14 varied between 33.2 and 39.4 per million person-years along the observed 30 year period, and the incidence of childhood leukaemia showed a moderate increase of 0.71% annually (p=0.0105). In the period of the hypothesized impact of the Chernobyl accident the incidence rate was elevated by 2.5% (95% CI: -8.1%; +14.3%), but this change was not statistically significant (p=0.663). The age standardised incidence, the age distribution, the gender ratio, and the magnitude of increasing trend of childhood leukaemia incidence in Hungary were similar to other European countries. Applying the presented interpolation method the authors did not find a statistically significant increase in the leukaemia incidence in the period of the hypothesized impact of the Chernobyl accident
International Nuclear Information System (INIS)
Iman, R.L.; Hora, S.C.
1988-01-01
Industry data representing the time to recovery of loss of off-site power at nuclear power plants for 63 incidents caused by plant-centered losses, grid losses, or severe weather losses are fit with exponential, lognormal, gamma and Weibull probability models. A Bayesian analysis is used to compare the adequacy of each of these models and to provide uncertainty bounds on each of the fitted models. A composite model that combines the probability models fitted to each of the three sources of data is presented as a method for predicting the time to recovery of loss of off-site power. The composite model is very general and can be made site specific by making adjustments on the models used, such as might occur due to the type of switchyard configuration or type of grid, and by adjusting the weights on the individual models, such as might occur with weather conditions existing at a particular plant. Adjustments in the composite model are shown for different models used for switchyard configuration and for different weights due to weather. Bayesian approaches are also presented for modeling the frequency of initiating events leading to loss of off-site power. One Bayesian model assumes that all plants share a common incidence rate for loss of off-site power, while the other Bayesian approach models the incidence rate for each plant relative to the incidence rates of all other plants. Combining the Bayesian models for the frequency of the initiating events with the composite Bayesian model for recovery provides the necessary vehicle for a complete model that incorporates uncertainty into a probabilistic risk assessment
International Nuclear Information System (INIS)
Kai, Michiaki; Kusama, Tomoko
2000-01-01
Breast cancer incidence is the highest risk due to radiation among atomic bomb survivors. The excess relative risk of the early-onset breast cancer seems to be remarkably high for the youngest age-at-exposure groups. The cancer risk estimate of breast cancer is a current issue in radiological protection. We used a two-stage stochastic model for carcinogenesis to analyze the breast cancer incidence among atomic bomb survivors (Kai, et al. Radiat. Res. 1997). Our purpose is to examine the dependence of radiation risk on age at exposure using the two-stage model and how to transfer it to other populations for radiological protection. We fitted the model assuming that radiation acts as an initiator and that the rate of radiation-induced mutation and background initiation mutation leading to baseline cancer are additive. We took two age-dependence, not attained age but age at exposure, of the spontaneous process into account. First, age-dependence of spontaneous initiation was expressed by a linear model. We also modeled the age-dependence of spontaneous net growth rate of initiated cells by a linear function. As far as radiation-induced initiation is concerned, we took a stepwise function other than a liner function into account. The analysis did not show that the radiation mutation for the youngest age-at-exposure groups below age 10 was higher than for the older groups. Furthermore, the incidence of female breast cancer in Japan is increasing and the birth cohort effect can be observed in atomic bomb survivors. Our model assumed that an acute exposure to atomic radiation can only initiate cancers and do not influence other stages of carcinogenesis, whereas spontaneous initiation and promotion are age-dependent to consider birth cohort effects. When these cohort effects are properly accounted for, the shape of the age-specific incidence curve in Japan is remarkably similar to the age-specific incidence in western populations (shown in figure). Recently Little and
Thresholding projection estimators in functional linear models
Cardot, Hervé; Johannes, Jan
2010-01-01
We consider the problem of estimating the regression function in functional linear regression models by proposing a new type of projection estimators which combine dimension reduction and thresholding. The introduction of a threshold rule allows to get consistency under broad assumptions as well as minimax rates of convergence under additional regularity hypotheses. We also consider the particular case of Sobolev spaces generated by the trigonometric basis which permits to get easily mean squ...
Daberkow, Kevin S.; Lin, Wei
2012-01-01
Nearly half a century of lottery scholarship has measured lottery tax incidence predominantly through either the Suits Index or regression analysis. The present study builds on historic lottery tax burden measurement to present a comprehensive set of tools to determine the tax incidence of individual games in addition to determining which lottery…
Incidence of social phobia and identification of its risk indicators: A model for prevention.
Acarturk, C.; Smit, H.F.E.; Graaf, de R.; Straten, van A.; Have, M. ten; Cuijpers, P.
2009-01-01
Objective: This study seeks to examine the incidence of social phobia in the general population and to establish a number of risk indicators. Method: Data were derived from the Netherlands Mental Health Survey and Incidence Study (NEMESIS) which is a population based prospective study (n = 7076). A
Elevated Incidence of Dental Caries in a Mouse Model of Cystic Fibrosis
Catalán, Marcelo A.; Scott-Anne, Kathleen; Klein, Marlise I.; Koo, Hyun; Bowen, William H.; Melvin, James E.
2011-01-01
Background Dental caries is the single most prevalent and costly infectious disease worldwide, affecting more than 90% of the population in the U.S. The development of dental cavities requires the colonization of the tooth surface by acid-producing bacteria, such as Streptococcus mutans. Saliva bicarbonate constitutes the main buffering system which neutralizes the pH fall generated by the plaque bacteria during sugar metabolism. We found that the saliva pH is severely decreased in a mouse model of cystic fibrosis disease (CF). Given the close relationship between pH and caries development, we hypothesized that caries incidence might be elevated in the mouse CF model. Methodology/Principal Findings We induced carious lesions in CF and wildtype mice by infecting their oral cavity with S. mutans, a well-studied cariogenic bacterium. After infection, the mice were fed a high-sucrose diet for 5 weeks (diet 2000). The mice were then euthanized and their jaws removed for caries scoring and bacterial counting. A dramatic increase in caries and severity of lesions scores were apparent in CF mice compared to their wildtype littermates. The elevated incidence of carious lesions correlated with a striking increase in the S. mutans viable population in dental plaque (20-fold increase in CF vs. wildtype mice; p value<0.003; t test). We also found that the pilocarpine-stimulated saliva bicarbonate concentration was significantly reduced in CF mice (16±2 mM vs. 31±2 mM, CF and wildtype mice, respectively; p value<0.01; t test). Conclusions/Significance Considering that bicarbonate is the most important pH buffering system in saliva, and the adherence and survival of aciduric bacteria such as S. mutans are enhanced at low pH values, we speculate that the decrease in the bicarbonate content and pH buffering of the saliva is at least partially responsible for the increased severity of lesions observed in the CF mouse. PMID:21304986
International Nuclear Information System (INIS)
Iwinski, Z.R.; Rosenberg, L.; Spruch, L.
1986-01-01
For potential scattering, with delta/sub L/(k) the phase shift modulo π for an incident wave number k, Levinson's theorem gives delta/sub L/(0)-delta/sub L/(infinity) in terms of N/sub L/, the number of bound states of angular momentum L, for delta/sub L/(k) assumed to be a continuous function of k. N/sub L/ also determines the number of nodes of the zero-energy wave function u/sub L/(r). A knowledge of the nodal structure and of the absolute value of delta/sub L/(0) is very useful in theoretical studies of low-energy potential scattering. Two preliminary attempts, one formal and one ''physical,'' are made to extend the above results to single-channel scattering by a compound system initially in its ground state. The nodal structure will be of greater interest to us here than an extension of Levinson's theorem
Directory of Open Access Journals (Sweden)
Erfan Ayubi
2017-05-01
Full Text Available OBJECTIVES The aim of this study was to explore the spatial pattern of female breast cancer (BC incidence at the neighborhood level in Tehran, Iran. METHODS The present study included all registered incident cases of female BC from March 2008 to March 2011. The raw standardized incidence ratio (SIR of BC for each neighborhood was estimated by comparing observed cases relative to expected cases. The estimated raw SIRs were smoothed by a Besag, York, and Mollie spatial model and the spatial empirical Bayesian method. The purely spatial scan statistic was used to identify spatial clusters. RESULTS There were 4,175 incident BC cases in the study area from 2008 to 2011, of which 3,080 were successfully geocoded to the neighborhood level. Higher than expected rates of BC were found in neighborhoods located in northern and central Tehran, whereas lower rates appeared in southern areas. The most likely cluster of higher than expected BC incidence involved neighborhoods in districts 3 and 6, with an observed-to-expected ratio of 3.92 (p<0.001, whereas the most likely cluster of lower than expected rates involved neighborhoods in districts 17, 18, and 19, with an observed-to-expected ratio of 0.05 (p<0.001. CONCLUSIONS Neighborhood-level inequality in the incidence of BC exists in Tehran. These findings can serve as a basis for resource allocation and preventive strategies in at-risk areas.
Ding, L; Li, J; Wang, C; Li, X; Su, Q; Zhang, G; Xue, F
2017-09-01
Prediction models of atrial fibrillation (AF) have been developed; however, there was no AF prediction model validated in Chinese population. Therefore, we aimed to investigate the incidence of AF in urban Han Chinese health check-up population, as well as to develop AF prediction models using behavioral, anthropometric, biochemical, electrocardiogram (ECG) markers, as well as visit-to-visit variability (VVV) in blood pressures available in the routine health check-up. A total of 33 186 participants aged 45-85 years and free of AF at baseline were included in this cohort, to follow up for incident AF with an annually routine health check-up. Cox regression models were used to develop AF prediction model and 10-fold cross-validation was used to test the discriminatory accuracy of prediction model. We developed three prediction models, with age, sex, history of coronary heart disease (CHD), hypertension as predictors for simple model, with left high-amplitude waves, premature beats added for ECG model, and with age, sex, history of CHD and VVV in systolic and diabolic blood pressures as predictors for VVV model, to estimate risk of incident AF. The calibration of our models ranged from 1.001 to 1.004 (P for Hosmer Lemeshow test >0.05). The area under receiver operator characteristics curve were 78%, 80% and 82%, respectively, for predicting risk of AF. In conclusion, we have identified predictors of incident AF and developed prediction models for AF with variables readily available in routine health check-up.
Yin, Ping; Mu, Lan; Madden, Marguerite; Vena, John E.
2014-10-01
Lung cancer is the second most commonly diagnosed cancer in both men and women in Georgia, USA. However, the spatio-temporal patterns of lung cancer risk in Georgia have not been fully studied. Hierarchical Bayesian models are used here to explore the spatio-temporal patterns of lung cancer incidence risk by race and gender in Georgia for the period of 2000-2007. With the census tract level as the spatial scale and the 2-year period aggregation as the temporal scale, we compare a total of seven Bayesian spatio-temporal models including two under a separate modeling framework and five under a joint modeling framework. One joint model outperforms others based on the deviance information criterion. Results show that the northwest region of Georgia has consistently high lung cancer incidence risk for all population groups during the study period. In addition, there are inverse relationships between the socioeconomic status and the lung cancer incidence risk among all Georgian population groups, and the relationships in males are stronger than those in females. By mapping more reliable variations in lung cancer incidence risk at a relatively fine spatio-temporal scale for different Georgian population groups, our study aims to better support healthcare performance assessment, etiological hypothesis generation, and health policy making.
A systemic approach for modeling soil functions
Vogel, Hans-Jörg; Bartke, Stephan; Daedlow, Katrin; Helming, Katharina; Kögel-Knabner, Ingrid; Lang, Birgit; Rabot, Eva; Russell, David; Stößel, Bastian; Weller, Ulrich; Wiesmeier, Martin; Wollschläger, Ute
2018-03-01
The central importance of soil for the functioning of terrestrial systems is increasingly recognized. Critically relevant for water quality, climate control, nutrient cycling and biodiversity, soil provides more functions than just the basis for agricultural production. Nowadays, soil is increasingly under pressure as a limited resource for the production of food, energy and raw materials. This has led to an increasing demand for concepts assessing soil functions so that they can be adequately considered in decision-making aimed at sustainable soil management. The various soil science disciplines have progressively developed highly sophisticated methods to explore the multitude of physical, chemical and biological processes in soil. It is not obvious, however, how the steadily improving insight into soil processes may contribute to the evaluation of soil functions. Here, we present to a new systemic modeling framework that allows for a consistent coupling between reductionist yet observable indicators for soil functions with detailed process understanding. It is based on the mechanistic relationships between soil functional attributes, each explained by a network of interacting processes as derived from scientific evidence. The non-linear character of these interactions produces stability and resilience of soil with respect to functional characteristics. We anticipate that this new conceptional framework will integrate the various soil science disciplines and help identify important future research questions at the interface between disciplines. It allows the overwhelming complexity of soil systems to be adequately coped with and paves the way for steadily improving our capability to assess soil functions based on scientific understanding.
Bayesian Modelling of Functional Whole Brain Connectivity
DEFF Research Database (Denmark)
Røge, Rasmus
the prevalent strategy of standardizing of fMRI time series and model data using directional statistics or we model the variability in the signal across the brain and across multiple subjects. In either case, we use Bayesian nonparametric modeling to automatically learn from the fMRI data the number......This thesis deals with parcellation of whole-brain functional magnetic resonance imaging (fMRI) using Bayesian inference with mixture models tailored to the fMRI data. In the three included papers and manuscripts, we analyze two different approaches to modeling fMRI signal; either we accept...... of funcional units, i.e. parcels. We benchmark the proposed mixture models against state of the art methods of brain parcellation, both probabilistic and non-probabilistic. The time series of each voxel are most often standardized using z-scoring which projects the time series data onto a hypersphere...
Mathematical modeling and visualization of functional neuroimages
DEFF Research Database (Denmark)
Rasmussen, Peter Mondrup
This dissertation presents research results regarding mathematical modeling in the context of the analysis of functional neuroimages. Specifically, the research focuses on pattern-based analysis methods that recently have become popular within the neuroimaging community. Such methods attempt...... sets are characterized by relatively few data observations in a high dimensional space. The process of building models in such data sets often requires strong regularization. Often, the degree of model regularization is chosen in order to maximize prediction accuracy. We focus on the relative influence...... be carefully selected, so that the model and its visualization enhance our ability to interpret the brain. The second part concerns interpretation of nonlinear models and procedures for extraction of ‘brain maps’ from nonlinear kernel models. We assess the performance of the sensitivity map as means...
The Goodwin model: behind the Hill function.
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Didier Gonze
Full Text Available The Goodwin model is a 3-variable model demonstrating the emergence of oscillations in a delayed negative feedback-based system at the molecular level. This prototypical model and its variants have been commonly used to model circadian and other genetic oscillators in biology. The only source of non-linearity in this model is a Hill function, characterizing the repression process. It was mathematically shown that to obtain limit-cycle oscillations, the Hill coefficient must be larger than 8, a value often considered unrealistic. It is indeed difficult to explain such a high coefficient with simple cooperative dynamics. We present here molecular models of the standard Goodwin model, based on single or multisite phosphorylation/dephosphorylation processes of a transcription factor, which have been previously shown to generate switch-like responses. We show that when the phosphorylation/dephosphorylation processes are fast enough, the limit-cycle obtained with a multisite phosphorylation-based mechanism is in very good quantitative agreement with the oscillations observed in the Goodwin model. Conditions in which the detailed mechanism is well approximated by the Goodwin model are given. A variant of the Goodwin model which displays sharp thresholds and relaxation oscillations is also explained by a double phosphorylation/dephosphorylation-based mechanism through a bistable behavior. These results not only provide rational support for the Goodwin model but also highlight the crucial role of the speed of post-translational processes, whose response curve are usually established at a steady state, in biochemical oscillators.
Correlation functions of two-matrix models
International Nuclear Information System (INIS)
Bonora, L.; Xiong, C.S.
1993-11-01
We show how to calculate correlation functions of two matrix models without any approximation technique (except for genus expansion). In particular we do not use any continuum limit technique. This allows us to find many solutions which are invisible to the latter technique. To reach our goal we make full use of the integrable hierarchies and their reductions which were shown in previous papers to naturally appear in multi-matrix models. The second ingredient we use, even though to a lesser extent, are the W-constraints. In fact an explicit solution of the relevant hierarchy, satisfying the W-constraints (string equation), underlies the explicit calculation of the correlation functions. The correlation functions we compute lend themselves to a possible interpretation in terms of topological field theories. (orig.)
Symmetries and modelling functions for diffusion processes
International Nuclear Information System (INIS)
Nikitin, A G; Spichak, S V; Vedula, Yu S; Naumovets, A G
2009-01-01
A constructive approach to the theory of diffusion processes is proposed, which is based on application of both symmetry analysis and the method of modelling functions. An algorithm for construction of the modelling functions is suggested. This algorithm is based on the error function expansion (ERFEX) of experimental concentration profiles. The high-accuracy analytical description of the profiles provided by ERFEX approximation allows a convenient extraction of the concentration dependence of diffusivity from experimental data and prediction of the diffusion process. Our analysis is exemplified by its employment in experimental results obtained for surface diffusion of lithium on the molybdenum (1 1 2) surface precovered with dysprosium. The ERFEX approximation can be directly extended to many other diffusion systems.
A mathematical model of avian influenza with half-saturated incidence.
Chong, Nyuk Sian; Tchuenche, Jean Michel; Smith, Robert J
2014-03-01
The widespread impact of avian influenza viruses not only poses risks to birds, but also to humans. The viruses spread from birds to humans and from human to human In addition, mutation in the primary strain will increase the infectiousness of avian influenza. We developed a mathematical model of avian influenza for both bird and human populations. The effect of half-saturated incidence on transmission dynamics of the disease is investigated. The half-saturation constants determine the levels at which birds and humans contract avian influenza. To prevent the spread of avian influenza, the associated half-saturation constants must be increased, especially the half-saturation constant H m for humans with mutant strain. The quantity H m plays an essential role in determining the basic reproduction number of this model. Furthermore, by decreasing the rate β m at which human-to-human mutant influenza is contracted, an outbreak can be controlled more effectively. To combat the outbreak, we propose both pharmaceutical (vaccination) and non-pharmaceutical (personal protection and isolation) control methods to reduce the transmission of avian influenza. Vaccination and personal protection will decrease β m, while isolation will increase H m. Numerical simulations demonstrate that all proposed control strategies will lead to disease eradication; however, if we only employ vaccination, it will require slightly longer to eradicate the disease than only applying non-pharmaceutical or a combination of pharmaceutical and non-pharmaceutical control methods. In conclusion, it is important to adopt a combination of control methods to fight an avian influenza outbreak.
Hazard identification based on plant functional modelling
International Nuclear Information System (INIS)
Rasmussen, B.; Whetton, C.
1993-10-01
A major objective of the present work is to provide means for representing a process plant as a socio-technical system, so as to allow hazard identification at a high level. The method includes technical, human and organisational aspects and is intended to be used for plant level hazard identification so as to identify critical areas and the need for further analysis using existing methods. The first part of the method is the preparation of a plant functional model where a set of plant functions link together hardware, software, operations, work organisation and other safety related aspects of the plant. The basic principle of the functional modelling is that any aspect of the plant can be represented by an object (in the sense that this term is used in computer science) based upon an Intent (or goal); associated with each Intent are Methods, by which the Intent is realized, and Constraints, which limit the Intent. The Methods and Constraints can themselves be treated as objects and decomposed into lower-level Intents (hence the procedure is known as functional decomposition) so giving rise to a hierarchical, object-oriented structure. The plant level hazard identification is carried out on the plant functional model using the Concept Hazard Analysis method. In this, the user will be supported by checklists and keywords and the analysis is structured by pre-defined worksheets. The preparation of the plant functional model and the performance of the hazard identification can be carried out manually or with computer support. (au) (4 tabs., 10 ills., 7 refs.)
Directory of Open Access Journals (Sweden)
Roman Bauer
Full Text Available Glioma is the most common form of primary brain tumor. Demographically, the risk of occurrence increases until old age. Here we present a novel computational model to reproduce the probability of glioma incidence across the lifespan. Previous mathematical models explaining glioma incidence are framed in a rather abstract way, and do not directly relate to empirical findings. To decrease this gap between theory and experimental observations, we incorporate recent data on cellular and molecular factors underlying gliomagenesis. Since evidence implicates the adult neural stem cell as the likely cell-of-origin of glioma, we have incorporated empirically-determined estimates of neural stem cell number, cell division rate, mutation rate and oncogenic potential into our model. We demonstrate that our model yields results which match actual demographic data in the human population. In particular, this model accounts for the observed peak incidence of glioma at approximately 80 years of age, without the need to assert differential susceptibility throughout the population. Overall, our model supports the hypothesis that glioma is caused by randomly-occurring oncogenic mutations within the neural stem cell population. Based on this model, we assess the influence of the (experimentally indicated decrease in the number of neural stem cells and increase of cell division rate during aging. Our model provides multiple testable predictions, and suggests that different temporal sequences of oncogenic mutations can lead to tumorigenesis. Finally, we conclude that four or five oncogenic mutations are sufficient for the formation of glioma.
Maximum entropy models of ecosystem functioning
International Nuclear Information System (INIS)
Bertram, Jason
2014-01-01
Using organism-level traits to deduce community-level relationships is a fundamental problem in theoretical ecology. This problem parallels the physical one of using particle properties to deduce macroscopic thermodynamic laws, which was successfully achieved with the development of statistical physics. Drawing on this parallel, theoretical ecologists from Lotka onwards have attempted to construct statistical mechanistic theories of ecosystem functioning. Jaynes’ broader interpretation of statistical mechanics, which hinges on the entropy maximisation algorithm (MaxEnt), is of central importance here because the classical foundations of statistical physics do not have clear ecological analogues (e.g. phase space, dynamical invariants). However, models based on the information theoretic interpretation of MaxEnt are difficult to interpret ecologically. Here I give a broad discussion of statistical mechanical models of ecosystem functioning and the application of MaxEnt in these models. Emphasising the sample frequency interpretation of MaxEnt, I show that MaxEnt can be used to construct models of ecosystem functioning which are statistical mechanical in the traditional sense using a savanna plant ecology model as an example
Maximum entropy models of ecosystem functioning
Energy Technology Data Exchange (ETDEWEB)
Bertram, Jason, E-mail: jason.bertram@anu.edu.au [Research School of Biology, The Australian National University, Canberra ACT 0200 (Australia)
2014-12-05
Using organism-level traits to deduce community-level relationships is a fundamental problem in theoretical ecology. This problem parallels the physical one of using particle properties to deduce macroscopic thermodynamic laws, which was successfully achieved with the development of statistical physics. Drawing on this parallel, theoretical ecologists from Lotka onwards have attempted to construct statistical mechanistic theories of ecosystem functioning. Jaynes’ broader interpretation of statistical mechanics, which hinges on the entropy maximisation algorithm (MaxEnt), is of central importance here because the classical foundations of statistical physics do not have clear ecological analogues (e.g. phase space, dynamical invariants). However, models based on the information theoretic interpretation of MaxEnt are difficult to interpret ecologically. Here I give a broad discussion of statistical mechanical models of ecosystem functioning and the application of MaxEnt in these models. Emphasising the sample frequency interpretation of MaxEnt, I show that MaxEnt can be used to construct models of ecosystem functioning which are statistical mechanical in the traditional sense using a savanna plant ecology model as an example.
International Nuclear Information System (INIS)
Ruben, A.; Maerten, H.; Seeliger, D.
1990-01-01
A complex statistical theory of fission neutron emission combined with a phenomenological fission model has been used to calculate fission neutron data for 238 U. Obtained neutron multiplicities and energy spectra as well as average fragment energies for incidence energies from threshold to 20 MeV (including multiple-chance fission) are compared with traditional data representations. (author). 19 refs, 6 figs
Boyle, Todd A; Mahaffey, Thomas; Mackinnon, Neil J; Deal, Heidi; Hallstrom, Lars K; Morgan, Holly
2011-03-01
Evidence suggests that the underreporting of medication errors and near misses, collectively referred to as medication incidents (MIs), in the community pharmacy setting, is high. Despite the obvious negative implications, MIs present opportunities for pharmacy staff and regulatory authorities to learn from these mistakes and take steps to reduce the likelihood that they reoccur. However, these activities can only take place if such errors are reported and openly discussed. This research proposes a model of factors influencing the reporting, service recovery, and organizational learning resulting from MIs within Canadian community pharmacies. The conceptual model is based on a synthesis of the literature and findings from a pilot study conducted among pharmacy management, pharmacists, and pharmacy technicians from 13 community pharmacies in Nova Scotia, Canada. The purpose of the pilot study was to identify various actions that should be taken to improve MI reporting and included staff perceptions of the strengths and weaknesses of their current MI-reporting process, desired characteristics of a new process, and broader external and internal activities that would likely improve reporting. Out of the 109 surveys sent, 72 usable surveys were returned (66.1% response rate). Multivariate analysis of variance found no significant differences among staff type in their perceptions of the current or new desired system but were found for broader initiatives to improve MI reporting. These findings were used for a proposed structural equation model (SEM). The SEM proposes that individual-perceived self-efficacy, MI process capability, MI process support, organizational culture, management support, and regulatory authority all influence the completeness of MI reporting, which, in turn, influences MI service recovery and learning. This model may eventually be used to enable pharmacy managers to make better decisions. By identifying risk factors that contribute to low MI
Madankan, Reza
All across the world, toxic material clouds are emitted from sources, such as industrial plants, vehicular traffic, and volcanic eruptions can contain chemical, biological or radiological material. With the growing fear of natural, accidental or deliberate release of toxic agents, there is tremendous interest in precise source characterization and generating accurate hazard maps of toxic material dispersion for appropriate disaster management. In this dissertation, an end-to-end framework has been developed for probabilistic source characterization and forecasting of atmospheric release incidents. The proposed methodology consists of three major components which are combined together to perform the task of source characterization and forecasting. These components include Uncertainty Quantification, Optimal Information Collection, and Data Assimilation. Precise approximation of prior statistics is crucial to ensure performance of the source characterization process. In this work, an efficient quadrature based method has been utilized for quantification of uncertainty in plume dispersion models that are subject to uncertain source parameters. In addition, a fast and accurate approach is utilized for the approximation of probabilistic hazard maps, based on combination of polynomial chaos theory and the method of quadrature points. Besides precise quantification of uncertainty, having useful measurement data is also highly important to warranty accurate source parameter estimation. The performance of source characterization is highly affected by applied sensor orientation for data observation. Hence, a general framework has been developed for the optimal allocation of data observation sensors, to improve performance of the source characterization process. The key goal of this framework is to optimally locate a set of mobile sensors such that measurement of textit{better} data is guaranteed. This is achieved by maximizing the mutual information between model predictions
Directory of Open Access Journals (Sweden)
Jennifer M Yeh
Full Text Available Although gastric cancer has declined dramatically in the US, the disease remains the second leading cause of cancer mortality worldwide. A better understanding of reasons for the decline can provide important insights into effective preventive strategies. We sought to estimate the contribution of risk factor trends on past and future intestinal-type noncardia gastric adenocarcinoma (NCGA incidence.We developed a population-based microsimulation model of intestinal-type NCGA and calibrated it to US epidemiologic data on precancerous lesions and cancer. The model explicitly incorporated the impact of Helicobacter pylori and smoking on disease natural history, for which birth cohort-specific trends were derived from the National Health and Nutrition Examination Survey (NHANES and National Health Interview Survey (NHIS. Between 1978 and 2008, the model estimated that intestinal-type NCGA incidence declined 60% from 11.0 to 4.4 per 100,000 men, <3% discrepancy from national statistics. H. pylori and smoking trends combined accounted for 47% (range = 30%-58% of the observed decline. With no tobacco control, incidence would have declined only 56%, suggesting that lower smoking initiation and higher cessation rates observed after the 1960s accelerated the relative decline in cancer incidence by 7% (range = 0%-21%. With continued risk factor trends, incidence is projected to decline an additional 47% between 2008 and 2040, the majority of which will be attributable to H. pylori and smoking (81%; range = 61%-100%. Limitations include assuming all other risk factors influenced gastric carcinogenesis as one factor and restricting the analysis to men.Trends in modifiable risk factors explain a significant proportion of the decline of intestinal-type NCGA incidence in the US, and are projected to continue. Although past tobacco control efforts have hastened the decline, full benefits will take decades to be realized, and further discouragement of smoking and
Yeh, Jennifer M; Hur, Chin; Schrag, Deb; Kuntz, Karen M; Ezzati, Majid; Stout, Natasha; Ward, Zachary; Goldie, Sue J
2013-01-01
Although gastric cancer has declined dramatically in the US, the disease remains the second leading cause of cancer mortality worldwide. A better understanding of reasons for the decline can provide important insights into effective preventive strategies. We sought to estimate the contribution of risk factor trends on past and future intestinal-type noncardia gastric adenocarcinoma (NCGA) incidence. We developed a population-based microsimulation model of intestinal-type NCGA and calibrated it to US epidemiologic data on precancerous lesions and cancer. The model explicitly incorporated the impact of Helicobacter pylori and smoking on disease natural history, for which birth cohort-specific trends were derived from the National Health and Nutrition Examination Survey (NHANES) and National Health Interview Survey (NHIS). Between 1978 and 2008, the model estimated that intestinal-type NCGA incidence declined 60% from 11.0 to 4.4 per 100,000 men, <3% discrepancy from national statistics. H. pylori and smoking trends combined accounted for 47% (range = 30%-58%) of the observed decline. With no tobacco control, incidence would have declined only 56%, suggesting that lower smoking initiation and higher cessation rates observed after the 1960s accelerated the relative decline in cancer incidence by 7% (range = 0%-21%). With continued risk factor trends, incidence is projected to decline an additional 47% between 2008 and 2040, the majority of which will be attributable to H. pylori and smoking (81%; range = 61%-100%). Limitations include assuming all other risk factors influenced gastric carcinogenesis as one factor and restricting the analysis to men. Trends in modifiable risk factors explain a significant proportion of the decline of intestinal-type NCGA incidence in the US, and are projected to continue. Although past tobacco control efforts have hastened the decline, full benefits will take decades to be realized, and further discouragement of smoking and reduction of
AN APPLICATION OF FUNCTIONAL MULTIVARIATE REGRESSION MODEL TO MULTICLASS CLASSIFICATION
Krzyśko, Mirosław; Smaga, Łukasz
2017-01-01
In this paper, the scale response functional multivariate regression model is considered. By using the basis functions representation of functional predictors and regression coefficients, this model is rewritten as a multivariate regression model. This representation of the functional multivariate regression model is used for multiclass classification for multivariate functional data. Computational experiments performed on real labelled data sets demonstrate the effectiveness of the proposed ...
Multivariate Heteroscedasticity Models for Functional Brain Connectivity
Directory of Open Access Journals (Sweden)
Christof Seiler
2017-12-01
Full Text Available Functional brain connectivity is the co-occurrence of brain activity in different areas during resting and while doing tasks. The data of interest are multivariate timeseries measured simultaneously across brain parcels using resting-state fMRI (rfMRI. We analyze functional connectivity using two heteroscedasticity models. Our first model is low-dimensional and scales linearly in the number of brain parcels. Our second model scales quadratically. We apply both models to data from the Human Connectome Project (HCP comparing connectivity between short and conventional sleepers. We find stronger functional connectivity in short than conventional sleepers in brain areas consistent with previous findings. This might be due to subjects falling asleep in the scanner. Consequently, we recommend the inclusion of average sleep duration as a covariate to remove unwanted variation in rfMRI studies. A power analysis using the HCP data shows that a sample size of 40 detects 50% of the connectivity at a false discovery rate of 20%. We provide implementations using R and the probabilistic programming language Stan.
International Nuclear Information System (INIS)
Prybutok, V.R.
1995-01-01
Risk associated with power generation must be identified to make intelligent choices between alternate power technologies. Radionuclide air stack emissions for a single coal plant and a single nuclear plant are used to compute the single plant leukemia incidence risk and total industry leukemia incidence risk. Leukemia incidence is the response variable as a function of radionuclide bone dose for the six proposed dose response curves considered. During normal operation a coal plant has higher radionuclide emissions than a nuclear plant and the coal industry has a higher leukaemia incidence risk than the nuclear industry, unless a nuclear accident occurs. Variation of nuclear accident size allows quantification of the impact of accidents on the total industry leukemia incidence risk comparison. The leukemia incidence risk is quantified as the number of accidents of a given size for the nuclear industry leukemia incidence risk to equal the coal industry leukemia incidence risk. The general linear model is used to develop equations that relate the accident frequency required for equal industry risks to the magnitude of the nuclear emission. Exploratory data analysis revealed that the relationship between the natural log of accident number versus the natural log of accident size is linear. (Author)
A Generic Modeling Process to Support Functional Fault Model Development
Maul, William A.; Hemminger, Joseph A.; Oostdyk, Rebecca; Bis, Rachael A.
2016-01-01
Functional fault models (FFMs) are qualitative representations of a system's failure space that are used to provide a diagnostic of the modeled system. An FFM simulates the failure effect propagation paths within a system between failure modes and observation points. These models contain a significant amount of information about the system including the design, operation and off nominal behavior. The development and verification of the models can be costly in both time and resources. In addition, models depicting similar components can be distinct, both in appearance and function, when created individually, because there are numerous ways of representing the failure space within each component. Generic application of FFMs has the advantages of software code reuse: reduction of time and resources in both development and verification, and a standard set of component models from which future system models can be generated with common appearance and diagnostic performance. This paper outlines the motivation to develop a generic modeling process for FFMs at the component level and the effort to implement that process through modeling conventions and a software tool. The implementation of this generic modeling process within a fault isolation demonstration for NASA's Advanced Ground System Maintenance (AGSM) Integrated Health Management (IHM) project is presented and the impact discussed.
Saha, Sukanta; Whiteford, Harvey; McGrath, John
2014-04-01
The aim of this study was to model estimates related to (a) the incidence of psychotic disorders and (b) the mortality associated with these disorders based on a large, population-based prevalence study. Data were drawn from the second national survey of adults with psychotic disorders conducted in seven Australian catchment areas during March to December 2010. To generate incidence rate estimates, we identified recent onset cases recruited as part of the prevalence study and then imputed population-based incidence rates using a set of conservative assumptions. Similarly, for mortality rates, we identified individuals who had died after being identified as 'screen-positive' for psychosis, but prior to full clinical assessment. Using a set of conservative assumptions, we then used these estimates to infer population-based mortality rates. Based on our models, we estimated that the incidence rate for psychotic disorders was 28 cases per 100,000 population. The rate estimates were significantly higher in males than females, with an overall male:female ratio of 1.57:1. Incidence rate estimates peaked in the youngest age group (18-24 years). The adjusted mortality rate estimated during the whole period of observation was 12.5 per 1000 persons, with a standardised mortality ratio of 5.5. Using treated prevalence data and observed deaths with appropriate algorithms, we were able to impute incidence and mortality rates for psychotic disorders consistent with the published literature. While the second national survey of psychotic disorders was not designed to identify mortality, our estimates provide a stark reminder of the increased mortality associated with these disorders.
Directory of Open Access Journals (Sweden)
Kamyar Mansori
2018-01-01
Full Text Available Objectives The aim of this study was to determine the factors associated with the spatial distribution of the incidence of colorectal cancer (CRC in the neighborhoods of Tehran, Iran using Bayesian spatial models. Methods This ecological study was implemented in Tehran on the neighborhood level. Socioeconomic variables, risk factors, and health costs were extracted from the Equity Assessment Study conducted in Tehran. The data on CRC incidence were extracted from the Iranian population-based cancer registry. The Besag-York-Mollié (BYM model was used to identify factors associated with the spatial distribution of CRC incidence. The software programs OpenBUGS version 3.2.3, ArcGIS 10.3, and GeoDa were used for the analysis. Results The Moran index was statistically significant for all the variables studied (p<0.05. The BYM model showed that having a women head of household (median standardized incidence ratio [SIR], 1.63; 95% confidence interval [CI], 1.06 to 2.53, living in a rental house (median SIR, 0.82; 95% CI, 0.71 to 0.96, not consuming milk daily (median SIR, 0.71; 95% CI, 0.55 to 0.94 and having greater household health expenditures (median SIR, 1.34; 95% CI, 1.06 to 1.68 were associated with a statistically significant elevation in the SIR of CRC. The median (interquartile range and mean (standard deviation values of the SIR of CRC, with the inclusion of all the variables studied in the model, were 0.57 (1.01 and 1.05 (1.31, respectively. Conclusions Inequality was found in the spatial distribution of CRC incidence in Tehran on the neighborhood level. Paying attention to this inequality and the factors associated with it may be useful for resource allocation and developing preventive strategies in atrisk areas.
Parisi function for two spin glass models
International Nuclear Information System (INIS)
Sibani, P.; Hertz, J.A.
1984-01-01
The probability distribution function P(q) for the overlap of pairs of metastable states and the associated Parisi order function q(x) are calculated exactly at zero temperature for two simple models. The first is a chain in which each spin interacts randomly with the sum of all the spins between it and one end of the chain; the second is an infinite-range limit of a spin glass version of Dyson's hierarchical model. Both have nontrivial overlap distributions: In the first case the problem reduces to a variable-step-length random walk problem, leading to q(x)=sin(πx). In the second model P(q) can be calculated by a simple recursion relation which generates devil's staircase structure in q(x). If the fraction p of antiferromagnetic bonds is less than 1/√2, the staircase is complete and the fractal dimensionality of the complement of the domain where q(x) is flat is log 2/log (1/p 2 ). In both models the space of metastable states can be described in terms of Cayley trees, which however have a different physical interpretation than in the S.K. model. (orig.)
Functional Security Model: Managers Engineers Working Together
Guillen, Edward Paul; Quintero, Rulfo
2008-05-01
Information security has a wide variety of solutions including security policies, network architectures and technological applications, they are usually designed and implemented by security architects, but in its own complexity this solutions are difficult to understand by company managers and they are who finally fund the security project. The main goal of the functional security model is to achieve a solid security platform reliable and understandable in the whole company without leaving of side the rigor of the recommendations and the laws compliance in a single frame. This paper shows a general scheme of the model with the use of important standards and tries to give an integrated solution.
Sivers function in constituent quark models
Scopetta, S.; Fratini, F.; Vento, V.
2008-01-01
A formalism to evaluate the Sivers function, developed for calculations in constituent quark models, is applied to the Isgur-Karl model. A non-vanishing Sivers asymmetry, with opposite signs for the u and d flavor, is found; the Burkardt sum rule is fulfilled up to 2 %. Nuclear effects in the extraction of neutron single spin asymmetries in semi-inclusive deep inelastic scattering off 3He are also evaluated. In the kinematics of JLab, it is found that the nuclear effects described by an Impulse Approximation approach are under control.
A general phenomenological model for work function
Brodie, I.; Chou, S. H.; Yuan, H.
2014-07-01
A general phenomenological model is presented for obtaining the zero Kelvin work function of any crystal facet of metals and semiconductors, both clean and covered with a monolayer of electropositive atoms. It utilizes the known physical structure of the crystal and the Fermi energy of the two-dimensional electron gas assumed to form on the surface. A key parameter is the number of electrons donated to the surface electron gas per surface lattice site or adsorbed atom, which is taken to be an integer. Initially this is found by trial and later justified by examining the state of the valence electrons of the relevant atoms. In the case of adsorbed monolayers of electropositive atoms a satisfactory justification could not always be found, particularly for cesium, but a trial value always predicted work functions close to the experimental values. The model can also predict the variation of work function with temperature for clean crystal facets. The model is applied to various crystal faces of tungsten, aluminium, silver, and select metal oxides, and most demonstrate good fits compared to available experimental values.
Mathematical Models of Cardiac Pacemaking Function
Li, Pan; Lines, Glenn T.; Maleckar, Mary M.; Tveito, Aslak
2013-10-01
Over the past half century, there has been intense and fruitful interaction between experimental and computational investigations of cardiac function. This interaction has, for example, led to deep understanding of cardiac excitation-contraction coupling; how it works, as well as how it fails. However, many lines of inquiry remain unresolved, among them the initiation of each heartbeat. The sinoatrial node, a cluster of specialized pacemaking cells in the right atrium of the heart, spontaneously generates an electro-chemical wave that spreads through the atria and through the cardiac conduction system to the ventricles, initiating the contraction of cardiac muscle essential for pumping blood to the body. Despite the fundamental importance of this primary pacemaker, this process is still not fully understood, and ionic mechanisms underlying cardiac pacemaking function are currently under heated debate. Several mathematical models of sinoatrial node cell membrane electrophysiology have been constructed as based on different experimental data sets and hypotheses. As could be expected, these differing models offer diverse predictions about cardiac pacemaking activities. This paper aims to present the current state of debate over the origins of the pacemaking function of the sinoatrial node. Here, we will specifically review the state-of-the-art of cardiac pacemaker modeling, with a special emphasis on current discrepancies, limitations, and future challenges.
Mathematical Models of Cardiac Pacemaking Function
Directory of Open Access Journals (Sweden)
Pan eLi
2013-10-01
Full Text Available Over the past half century, there has been intense and fruitful interaction between experimental and computational investigations of cardiac function. This interaction has, for example, led to deep understanding of cardiac excitation-contraction coupling; how it works, as well as how it fails. However, many lines of inquiry remain unresolved, among them the initiation of each heartbeat. The sinoatrial node, a cluster of specialized pacemaking cells in the right atrium of the heart, spontaneously generates an electro-chemical wave that spreads through the atria and through the cardiac conduction system to the ventricles, initiating the contraction of cardiac muscle essential for pumping blood to the body. Despite the fundamental importance of this primary pacemaker, this process is still not fully understood, and ionic mechanisms underlying cardiac pacemaking function are currently under heated debate. Several mathematical models of sinoatrial node cell membrane electrophysiology have been constructed as based on different experimental data sets and hypotheses. As could be expected, these differing models offer diverse predictions about cardiac pacemaking activities. This paper aims to present the current state of debate over the origins of the pacemaking function of the sinoatrial node. Here, we will specifically review the state-of-the-art of cardiac pacemaker modeling, with a special emphasis on current discrepancies, limitations, and future challenges.
Age-period-cohort modelling of breast cancer incidence in the Nordic countries
DEFF Research Database (Denmark)
Rostgaard, K; Vaeth, M; Holst, H
2001-01-01
into account. Assuming the age dependency of the incidence pattern in old age to be common for the Nordic countries, an internal comparison could be made among the four countries of the cohort effects and the period effects. The study indicated that the period effects have been of importance for the increase...... in breast cancer incidence seen in the Nordic countries. The widespread practice of neglecting the period effects in age-period-cohort analysis of time trends in breast cancer incidence therefore probably needs reconsideration. A key finding was that Danish women born in the 20th century seem to have been...... exposed to an increasing load of cohort borne breast cancer risk factors not experienced to the same extent by Norwegian women, whereas they were seemingly subjected to the same period effects....
Development of a model for recording and evaluating incidents in radiotherapy
International Nuclear Information System (INIS)
Ribeiro, A.L.C.; Paiva, E. de; Teixeira, F.C.S.
2017-01-01
Radiotherapy has been constantly improving to become increasingly effective, thus contributing to increase the chances of healing patients. In this sense, incident learning gained prominence during successive approaches to patient safety. The objective is to develop a tool for recording and analyzing incidents in radiotherapy and applying it to clinics in Rio de Janeiro in order to implement the policy of quality management and safety culture. Steps were taken that involved the analysis of the process maps for the enrichment of the system (called the Standardized System of Incidents in Radiotherapy - SPIRad) that already has a version in physical form. The proposal is the conversion of this form to a digital tool to be used through the intranet. The next step is to apply it to radiotherapy clinics in Rio de Janeiro and evaluate the results obtained with the objective of possible improvements through feedback from users
Directory of Open Access Journals (Sweden)
Oilson Alberto Gonzatto Junior
2017-06-01
Full Text Available Data with excess zeros are frequently found in practice, and the recommended analysis is to use models that adequately address the counting of zero observations. In this study, the Zero Inflated Beta Regression Model (BeZI was used on experimental data to describe the mean incidence of leaf citrus canker in orange groves under the influence of genotype and rootstocks of origin. Based on the model, it was possible to quantify the odds that a null observation to mean incidence comes from a particular plant according to genotype and rootstock, and estimate its expected value according to this combination. Laranja Caipira rootstock proved to be the most resistant to leaf citrus canker as well as Limão Cravo proved to be the most fragile. The Ipiguá IAC, Arapongas, EEL and Olímpia genotypes have statistically equivalent chances.
Directory of Open Access Journals (Sweden)
Ashraf T Soliman
2013-01-01
was found between ferritin and TSH. Conclusions: Worsening of thyroid function was observed in 35% of the studied thalassemic patients by the age of 18 years. The lack of proper increase of TSH in response to the low circulating levels of FT4 in 13/17 (76% of these patients indicates a relatively high incidence of defective pituitary thyrotrophic function in these patients.
Main pumps lost incident in the nuclear power plant Atucha I. Modelling with RELAP5/MOD3.2
International Nuclear Information System (INIS)
Ventura, M.A.; Rosso, R.D.
1998-01-01
Time evolution of natural circulation in the nuclear power plant Atucha I (CNA-I), in a main pumps lost incident because of the lost of external power feed, is analyzed. It leads to a strong stop transient, without an important blow down, from a forced nominal flow to a natural circulation one. The results are obtained from RELAP5/MOD3.2 code's modeling. The study is based on the refrigeration conditions analysis, during the first minutes of the reactor out of service. Previously to the transient, work had been done to obtain the plant steady state, with design parameters in operation conditions at 100 % of power. The object is that the actual plant state would be represented. In this way, each plant part (steam generators, reactor, pressurizer, pumps) had been modeled in separated form with the appropriate boundary conditions, to be used in the whole circuit simulation. The developed model, had been validated making use of the comparison between the values obtained to the principal thermodynamic parameters with the plant recorded values, in the same incident. The results are satisfactory in a way. On the other hand, it has suggested some modeling changes. The RELAP5/MOD3.2 capability to model the thermodynamic phenomena in a PHWR plant has been verified when, according to the mentioned incident, the flow pass from a nominal forced flow, to one which is governed by natural circulation, still with the CNA-I untypical design conditions. (author) [es
Modeling of sintering of functionally gradated materials
International Nuclear Information System (INIS)
Gasik, M.; Zhang, B.
2001-01-01
The functionally gradated materials (FGMs) are distinguished from isotropic materials by gradients of composition, phase distribution, porosity, and related properties. For FGMs made by powder metallurgy, sintering control is one of the most important factors. In this study sintering process of FGMs is modeled and simulated with a computer. A new modeling approach was used to formulate equation systems and the model for sintering of gradated hard metals, coupled with heat transfer and grain growth. A FEM module was developed to simulate FGM sintering in conventional, microwave and hybrid conditions, to calculate density, stress and temperature distribution. Behavior of gradated WC-Co hardmetal plate and cone specimens was simulated for various conditions, such as mean particle size, green density distribution and cobalt gradation parameter. The results show that the deformation behavior and stress history of graded powder compacts during heating, sintering and cooling could be predicted for optimization of sintering process. (author)
International Nuclear Information System (INIS)
Ten Haken, R.K.; Awschalom, M.; Rosenberg, I.
1982-11-01
Neutron absorbed dose yields (absorbed dose rates per unit incident current on targets at a given SAD or SSD) increase with incident charged particle energy for both protons and deuterons. Analyses of neutron dose yield versus incident particle energy have been performed for both deuterons and protons. It is the purpose of this report to update those analyses by pooling all of the more recent published results and to reanalyze the trend of yield, Y, versus incident energy, E, which in the past has been described by an expression of the form Y = aE/sup b/, where a and b are empirical constants. From the reanalyzed trend it is concluded that for a given size cyclotron (E/sub p/ = 2E/sub d/), the dose yields using protons are higher than those using deuterons up to a proton energy E/sub p/ of 64 MeV
Kim, Sun Bean; Yoon, Myoungho; Ku, Nam Su; Kim, Min Hyung; Song, Je Eun; Ahn, Jin Young; Jeong, Su Jin; Kim, Changsoo; Kwon, Hee-Dae; Lee, Jeehyun; Smith, Davey M; Choi, Jun Yong
2014-01-01
Multiple prevention measures have the possibility of impacting HIV incidence in South Korea, including early diagnosis, early treatment, and pre-exposure prophylaxis (PrEP). We investigated how each of these interventions could impact the local HIV epidemic, especially among men who have sex with men (MSM), who have become the major risk group in South Korea. A mathematical model was used to estimate the effects of each these interventions on the HIV epidemic in South Korea over the next 40 years, as compared to the current situation. We constructed a mathematical model of HIV infection among MSM in South Korea, dividing the MSM population into seven groups, and simulated the effects of early antiretroviral therapy (ART), early diagnosis, PrEP, and combination interventions on the incidence and prevalence of HIV infection, as compared to the current situation that would be expected without any new prevention measures. Overall, the model suggested that the most effective prevention measure would be PrEP. Even though PrEP effectiveness could be lessened by increased unsafe sex behavior, PrEP use was still more beneficial than the current situation. In the model, early diagnosis of HIV infection was also effectively decreased HIV incidence. However, early ART did not show considerable effectiveness. As expected, it would be most effective if all interventions (PrEP, early diagnosis and early treatment) were implemented together. This model suggests that PrEP and early diagnosis could be a very effective way to reduce HIV incidence in South Korea among MSM.
Functionalized anatomical models for EM-neuron Interaction modeling
Neufeld, Esra; Cassará, Antonino Mario; Montanaro, Hazael; Kuster, Niels; Kainz, Wolfgang
2016-06-01
The understanding of interactions between electromagnetic (EM) fields and nerves are crucial in contexts ranging from therapeutic neurostimulation to low frequency EM exposure safety. To properly consider the impact of in vivo induced field inhomogeneity on non-linear neuronal dynamics, coupled EM-neuronal dynamics modeling is required. For that purpose, novel functionalized computable human phantoms have been developed. Their implementation and the systematic verification of the integrated anisotropic quasi-static EM solver and neuronal dynamics modeling functionality, based on the method of manufactured solutions and numerical reference data, is described. Electric and magnetic stimulation of the ulnar and sciatic nerve were modeled to help understanding a range of controversial issues related to the magnitude and optimal determination of strength-duration (SD) time constants. The results indicate the importance of considering the stimulation-specific inhomogeneous field distributions (especially at tissue interfaces), realistic models of non-linear neuronal dynamics, very short pulses, and suitable SD extrapolation models. These results and the functionalized computable phantom will influence and support the development of safe and effective neuroprosthetic devices and novel electroceuticals. Furthermore they will assist the evaluation of existing low frequency exposure standards for the entire population under all exposure conditions.
Mass functions from the excursion set model
Hiotelis, Nicos; Del Popolo, Antonino
2017-11-01
Aims: We aim to study the stochastic evolution of the smoothed overdensity δ at scale S of the form δ(S) = ∫0S K(S,u)dW(u), where K is a kernel and dW is the usual Wiener process. Methods: For a Gaussian density field, smoothed by the top-hat filter, in real space, we used a simple kernel that gives the correct correlation between scales. A Monte Carlo procedure was used to construct random walks and to calculate first crossing distributions and consequently mass functions for a constant barrier. Results: We show that the evolution considered here improves the agreement with the results of N-body simulations relative to analytical approximations which have been proposed from the same problem by other authors. In fact, we show that an evolution which is fully consistent with the ideas of the excursion set model, describes accurately the mass function of dark matter haloes for values of ν ≤ 1 and underestimates the number of larger haloes. Finally, we show that a constant threshold of collapse, lower than it is usually used, it is able to produce a mass function which approximates the results of N-body simulations for a variety of redshifts and for a wide range of masses. Conclusions: A mass function in good agreement with N-body simulations can be obtained analytically using a lower than usual constant collapse threshold.
Lung cancer incidence after smoking and exposure to radon using a two-mutation model
International Nuclear Information System (INIS)
Leenhouts, H.P.
1997-01-01
A study to analyze lung cancer in humans as a function of exposure to radon and smoking, used three types of data: population statistics in non-smokers habits of British radiologists and radon exposure of the Colorado uranium miners. Using a simplified two-mutation carcinogenesis model and only six unknown variables yielded a coherent description of lung cancer dependence on exposure to radon and smoking. For risk estimates the radiation effect of radon can be concluded to be highly dependent on smoking habits, e.g. the radiation effect differs (in absolute terms) by a factor of about 7 between non-smokers, but the relative risk is much higher in non-smokers than in smokers. The results to data justify a thorough investigation of the analysis method to realize improved radon risk estimates. (author)
Lung cancer incidence after smoking and exposure to radon using a two-mutation model
Energy Technology Data Exchange (ETDEWEB)
Leenhouts, H.P. [RIVM, Bilthoven (Netherlands)
1997-03-01
A study to analyze lung cancer in humans as a function of exposure to radon and smoking, used three types of data: population statistics in non-smokers habits of British radiologists and radon exposure of the Colorado uranium miners. Using a simplified two-mutation carcinogenesis model and only six unknown variables yielded a coherent description of lung cancer dependence on exposure to radon and smoking. For risk estimates the radiation effect of radon can be concluded to be highly dependent on smoking habits, e.g. the radiation effect differs (in absolute terms) by a factor of about 7 between non-smokers, but the relative risk is much higher in non-smokers than in smokers. The results to data justify a thorough investigation of the analysis method to realize improved radon risk estimates. (author)
International Nuclear Information System (INIS)
Berceanu, I.; Andronic, A.; Duma, M.
1998-01-01
Non-statistical fluctuations in the excitation functions (EF) of dissipative heavy ion collisions (DHIC) was rather unexpected due to the fact that cross sections are always obtained on a 'coarse cell' of TKEL and θ cm . The contribution of a large number of microchannels, N, is expected to attenuate the amplitude of such fluctuations as σ(E) has a χ 2 distribution with 2N degrees of freedom. In the framework of the Partially Overlapping Molecular Levels the observation of the fluctuations of the cross section as a function of the incident energy is explained by the fact that the levels of the dinuclear system formed in the first stage of a dissipative process are excited in a region of low density situated in the vicinity of the yrast line. The time evolution of dinuclear (DNS) system with different mass asymmetries with the total mass of the nuclear system 19 F + 27 Al system configuration and its time evolution, the excitation function for this system has been measured between 111.4 MeV and 136.9 MeV with a 250 keV energy step. Fluctuations with amplitude larger than the statistical errors were observed. Large Z and angular cross correlation coefficients show their nonstatistical nature. An average energy correlation width of 170±65 keV, to which corresponds a DNS lifetime τ int (3.9 ± 1.1)·10 -21 s, was obtained by the energy autocorrelation function (EAF). The experimental EAF secondary structure period agrees with that predicted by Kun model when the deformation of the outgoing fragments is taken into account. To get more insight in the reaction mechanism, the dependence of the charge distribution variance for two total kinetic energy loss windows, W1 = 20 ± 2.5 and W2 = 30 ± 2.5 MeV, was obtained as a function of E lab . The second moments of the experimental charge distributions have been calculated and the obtained values were represented for W1 and W2. Fluctuations with quite large amplitude are present. In a transport approach of deep inelastic
International Nuclear Information System (INIS)
Steiner, Martin; Karcher, Klaus; Nosske, Dietmar
2012-01-01
The radiation exposure after a short-term release of radioactive substances is often calculated assuming equilibrium conditions. An example is that of the German Incident Calculation Bases for nuclear power plants with pressurized water reactors. Here, the contamination of human milk is calculated using transfer factors. Applying this equilibrium model to incident situations raises the question whether baby's radiation exposure is adequately assessed. This contribution shows that compliance with the relevant dose limits of paragraph 49 of the German Radiation Protection Ordinance is ensured for design basis accidents on the assumption that the hypothetical breastfeeding period starts at the beginning of the activity release. Comparative analyses were performed against the biokinetic models applied by ICRP for radiation protection purposes, taking the reference nuclides 137 Cs, 90 Sr, 131 I, 241 Am and long-lived plutonium isotopes as examples. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Steiner, Martin; Karcher, Klaus; Nosske, Dietmar [Bundesamt fuer Strahlenschutz, Oberschleissheim (Germany)
2012-06-15
The radiation exposure after a short-term release of radioactive substances is often calculated assuming equilibrium conditions. An example is that of the German Incident Calculation Bases for nuclear power plants with pressurized water reactors. Here, the contamination of human milk is calculated using transfer factors. Applying this equilibrium model to incident situations raises the question whether baby's radiation exposure is adequately assessed. This contribution shows that compliance with the relevant dose limits of paragraph 49 of the German Radiation Protection Ordinance is ensured for design basis accidents on the assumption that the hypothetical breastfeeding period starts at the beginning of the activity release. Comparative analyses were performed against the biokinetic models applied by ICRP for radiation protection purposes, taking the reference nuclides {sup 137}Cs, {sup 90}Sr, {sup 131}I, {sup 241}Am and long-lived plutonium isotopes as examples. (orig.)
Directory of Open Access Journals (Sweden)
Ruche Guy
2011-06-01
Full Text Available Abstract Background During the last decades, dengue viruses have spread throughout the Americas region, with an increase in the number of severe forms of dengue. The surveillance system in Guadeloupe (French West Indies is currently operational for the detection of early outbreaks of dengue. The goal of the study was to improve this surveillance system by assessing a modelling tool to predict the occurrence of dengue epidemics few months ahead and thus to help an efficient dengue control. Methods The Box-Jenkins approach allowed us to fit a Seasonal Autoregressive Integrated Moving Average (SARIMA model of dengue incidence from 2000 to 2006 using clinical suspected cases. Then, this model was used for calculating dengue incidence for the year 2007 compared with observed data, using three different approaches: 1 year-ahead, 3 months-ahead and 1 month-ahead. Finally, we assessed the impact of meteorological variables (rainfall, temperature and relative humidity on the prediction of dengue incidence and outbreaks, incorporating them in the model fitting the best. Results The 3 months-ahead approach was the most appropriate for an effective and operational public health response, and the most accurate (Root Mean Square Error, RMSE = 0.85. Relative humidity at lag-7 weeks, minimum temperature at lag-5 weeks and average temperature at lag-11 weeks were variables the most positively correlated to dengue incidence in Guadeloupe, meanwhile rainfall was not. The predictive power of SARIMA models was enhanced by the inclusion of climatic variables as external regressors to forecast the year 2007. Temperature significantly affected the model for better dengue incidence forecasting (p-value = 0.03 for minimum temperature lag-5, p-value = 0.02 for average temperature lag-11 but not humidity. Minimum temperature at lag-5 weeks was the best climatic variable for predicting dengue outbreaks (RMSE = 0.72. Conclusion Temperature improves dengue outbreaks forecasts
Mousam, Aneela; Maggioni, Viviana; Delamater, Paul L.; Quispe, Antonio M.
2017-10-01
Between 2001 and 2010 significant progress was made towards reducing the number of malaria cases in Peru; however, the country saw an increase between 2011 and 2015. This work attempts to uncover the associations among various climatic and environmental variables and the annual malaria parasite incidence in the Peruvian region of Loreto. A Multilevel Mixed-effects Poisson Regression model is employed, focusing on the 2009-2013 period, when trends in malaria incidence shifted from decreasing to increasing. The results indicate that variations in elevation (β = 0.78; 95% confidence interval (CI), 0.75-0.81), soil moisture (β = 0.0021; 95% CI, 0.0019-0.0022), rainfall (β = 0.59; 95% CI, 0.56-0.61), and normalized difference vegetation index (β = 2.13; 95% CI, 1.83-2.43) is associated with higher annual parasite incidence, whereas an increase in temperature (β = -0.0043; 95% CI, - 0.0044- 0.0041) is associated with a lower annual parasite incidence. The results from this study are particularly useful for healthcare workers in Loreto and have the potential of being integrated within malaria elimination plans.
Electricity price forecasting through transfer function models
International Nuclear Information System (INIS)
Nogales, F.J.; Conejo, A.J.
2006-01-01
Forecasting electricity prices in present day competitive electricity markets is a must for both producers and consumers because both need price estimates to develop their respective market bidding strategies. This paper proposes a transfer function model to predict electricity prices based on both past electricity prices and demands, and discuss the rationale to build it. The importance of electricity demand information is assessed. Appropriate metrics to appraise prediction quality are identified and used. Realistic and extensive simulations based on data from the PJM Interconnection for year 2003 are conducted. The proposed model is compared with naive and other techniques. Journal of the Operational Research Society (2006) 57, 350-356.doi:10.1057/palgrave.jors.2601995; published online 18 May 2005. (author)
Signed distance function implicit geologic modeling
Directory of Open Access Journals (Sweden)
Roberto Mentzingen Rolo
Full Text Available Abstract Prior to every geostatistical estimation or simulation study there is a need for delimiting the geologic domains of the deposit, which is traditionally done manually by a geomodeler in a laborious, time consuming and subjective process. For this reason, novel techniques referred to as implicit modelling have appeared. These techniques provide algorithms that replace the manual digitization process of the traditional methods by some form of automatic procedure. This paper covers a few well established implicit methods currently available with special attention to the signed distance function methodology. A case study based on a real dataset was performed and its applicability discussed. Although it did not replace an experienced geomodeler, the method proved to be capable in creating semi-automatic geological models from the sampling data, especially in the early stages of exploration.
Directory of Open Access Journals (Sweden)
Ujué Fresán
2016-10-01
Full Text Available Obesity is a major epidemic for developed countries in the 21st century. The main cause of obesity is energy imbalance, of which contributing factors include a sedentary lifestyle, epigenetic factors and excessive caloric intake through food and beverages. A high consumption of caloric beverages, such as alcoholic or sweetened drinks, may particularly contribute to weight gain, and lower satiety has been associated with the intake of liquid instead of solid calories. Our objective was to evaluate the association between the substitution of a serving per day of water for another beverage (or group of them and the incidence of obesity and weight change in a Mediterranean cohort, using mathematical models. We followed 15,765 adults without obesity at baseline. The intake of 17 beverage items was assessed at baseline through a validated food-frequency questionnaire. The outcomes were average change in body weight in a four-year period and new-onset obesity and their association with the substitution of one serving per day of water for one of the other beverages. During the follow-up, 873 incident cases of obesity were identified. In substitution models, the consumption of water instead of beer or sugar-sweetened soda beverages was associated with a lower obesity incidence (the Odds Ratio (OR 0.80 (95% confidence interval (CI 0.68 to 0.94 and OR 0.85 (95% CI 0.75 to 0.97; respectively and, in the case of beer, it was also associated with a higher average weight loss (weight change difference = −328 g; (95% CI −566 to −89. Thus, this study found that replacing one sugar-sweetened soda beverage or beer with one serving of water per day at baseline was related to a lower incidence of obesity and to a higher weight loss over a four-year period time in the case of beer, based on mathematical models.
Lo, Nathan C; Gupta, Ribhav; Stanaway, Jeffrey D; Garrett, Denise O; Bogoch, Isaac I; Luby, Stephen P; Andrews, Jason R
2018-02-12
Typhoid fever remains a major public health problem globally. While new Vi conjugate vaccines hold promise for averting disease, the optimal programmatic delivery remains unclear. We aimed to identify the strategies and associated epidemiologic conditions under which Vi conjugate vaccines would be cost-effective. We developed a dynamic, age-structured transmission and cost-effectiveness model that simulated multiple vaccination strategies with a typhoid Vi conjugate vaccine from a societal perspective. We simulated 10-year vaccination programs with (1) routine immunization of infants (aged typhoid fever and defined strategies as highly cost-effective by using the definition of a low-income country (defined as a country with a gross domestic product of $1045 per capita). We defined incidence as the true number of clinically symptomatic people in the population per year. Vi conjugate typhoid vaccines were highly cost-effective when administered by routine immunization activities through the EPI in settings with an annual incidence of >50 cases/100000 (95% uncertainty interval, 40-75 cases) and when administered through the EPI plus a catch-up campaign in settings with an annual incidence of >130 cases/100000 (95% uncertainty interval, 50-395 cases). The incidence threshold was sensitive to the typhoid-related case-fatality rate, carrier contribution to transmission, vaccine characteristics, and country-specific economic threshold for cost-effectiveness. Typhoid Vi conjugate vaccines would be highly cost-effective in low-income countries in settings of moderate typhoid incidence (50 cases/100000 annually). These results were sensitive to case-fatality rates, underscoring the need to consider factors contributing to typhoid mortality (eg, healthcare access and antimicrobial resistance) in the global vaccination strategy. © The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America.
Gu, Liubao; Huang, Liji; Wu, Haidi; Lou, Qinglin; Bian, Rongwen
2017-05-01
Serum uric acid has shown to be a predictor of renal disease progression in most but not all studies. This study aims to test whether renal function-normalized serum uric acid is superior to serum uric acid as the predictor of incident chronic kidney disease in type 2 diabetes mellitus patients. In this study, 1339 type 2 diabetes mellitus patients with estimated glomerular filtration rate ⩾60 mL/min/1.73 m 2 and normouricemia were included. Renal function-normalized serum uric acid was calculated using serum uric acid/creatinine. Cox regression analysis was used to estimate the association between serum uric acid, renal function-normalized serum uric acid and incident chronic kidney disease. In total, 74 (5.53%) patients developed to chronic kidney disease 3 or greater during a median follow-up of 4 years, with older ages, longer diabetes duration and lower estimated glomerular filtration rate at baseline. The decline rate of estimated glomerular filtration rate was positively correlated with serum uric acid/creatinine ( r = 0.219, p uric acid ( r = 0.005, p = 0.858). Moreover, multivariate analysis revealed that serum uric acid was not an independent risk factor for incident chronic kidney disease ( p = 0.055), whereas serum uric acid to creatinine ratio was significantly associated with incident chronic kidney disease independently of potential confounders including baseline estimated glomerular filtration rate. serum uric acid to creatinine ratio might be a better predictor of incident chronic kidney disease in type 2 diabetes mellitus patients.
Silencing of the rotavirus NSP4 protein decreases the incidence of biliary atresia in murine model.
Directory of Open Access Journals (Sweden)
Jiexiong Feng
Full Text Available Biliary atresia is a common disease in neonates which causes obstructive jaundice and progressive hepatic fibrosis. Our previous studies indicate that rotavirus infection is an initiator in the pathogenesis of experimental biliary atresia (BA through the induction of increased nuclear factor-kappaB and abnormal activation of the osteopontin inflammation pathway. In the setting of rotavirus infection, rotavirus nonstructural protein 4 (NSP4 serves as an important immunogen, viral protein 7 (VP7 is necessary in rotavirus maturity and viral protein 4 (VP4 is a virulence determiner. The purpose of the current study is to clarify the roles of NSP4, VP7 and VP4 in the pathogenesis of experimental BA. Primary cultured extrahepatic biliary epithelia were infected with Rotavirus (mmu18006. Small interfering RNA targeting NSP4, VP7 or VP4 was transfected before rotavirus infection both in vitro and in vivo. We analyzed the incidence of BA, morphological change, morphogenesis of viral particles and viral mRNA and protein expression. The in vitro experiments showed NSP4 silencing decreased the levels of VP7 and VP4, reduced viral particles and decreased cytopathic effect. NSP4-positive cells had strongly positive expression of integrin subunit α2. Silencing of VP7 or VP4 partially decreased epithelial injury. Animal experiments indicated after NSP4 silencing, mouse pups had lower incidence of BA than after VP7 or VP4 silencing. However, 33.3% of VP4-silenced pups (N = 6 suffered BA and 50% of pups (N = 6 suffered biliary injury after VP7 silencing. Hepatic injury was decreased after NSP4 or VP4 silencing. Neither VP4 nor VP7 were detected in the biliary ducts after NSP4. All together, NSP4 silencing down-regulates VP7 and VP4, resulting in decreased incidence of BA.
Medicare capitation model, functional status, and multiple comorbidities: model accuracy
Noyes, Katia; Liu, Hangsheng; Temkin-Greener, Helena
2012-01-01
Objective This study examined financial implications of CMS-Hierarchical Condition Categories (HCC) risk-adjustment model on Medicare payments for individuals with comorbid chronic conditions. Study Design The study used 1992-2000 data from the Medicare Current Beneficiary Survey and corresponding Medicare claims. The pairs of comorbidities were formed based on the prior evidence about possible synergy between these conditions and activities of daily living (ADL) deficiencies and included heart disease and cancer, lung disease and cancer, stroke and hypertension, stroke and arthritis, congestive heart failure (CHF) and osteoporosis, diabetes and coronary artery disease, CHF and dementia. Methods For each beneficiary, we calculated the actual Medicare cost ratio as the ratio of the individual’s annualized costs to the mean annual Medicare cost of all people in the study. The actual Medicare cost ratios, by ADLs, were compared to the HCC ratios under the CMS-HCC payment model. Using multivariate regression models, we tested whether having the identified pairs of comorbidities affects the accuracy of CMS-HCC model predictions. Results The CMS-HCC model underpredicted Medicare capitation payments for patients with hypertension, lung disease, congestive heart failure and dementia. The difference between the actual costs and predicted payments was partially explained by beneficiary functional status and less than optimal adjustment for these chronic conditions. Conclusions Information about beneficiary functional status should be incorporated in reimbursement models since underpaying providers for caring for population with multiple comorbidities may provide severe disincentives for managed care plans to enroll such individuals and to appropriately manage their complex and costly conditions. PMID:18837646
Correlation Functions in Holographic Minimal Models
Papadodimas, Kyriakos
2012-01-01
We compute exact three and four point functions in the W_N minimal models that were recently conjectured to be dual to a higher spin theory in AdS_3. The boundary theory has a large number of light operators that are not only invisible in the bulk but grow exponentially with N even at small conformal dimensions. Nevertheless, we provide evidence that this theory can be understood in a 1/N expansion since our correlators look like free-field correlators corrected by a power series in 1/N . However, on examining these corrections we find that the four point function of the two bulk scalar fields is corrected at leading order in 1/N through the contribution of one of the additional light operators in an OPE channel. This suggests that, to correctly reproduce even tree-level correlators on the boundary, the bulk theory needs to be modified by the inclusion of additional fields. As a technical by-product of our analysis, we describe two separate methods -- including a Coulomb gas type free-field formalism -- that ...
Directory of Open Access Journals (Sweden)
Wei Wu
Full Text Available Cases of hemorrhagic fever with renal syndrome (HFRS are widely distributed in eastern Asia, especially in China, Russia, and Korea. It is proved to be a difficult task to eliminate HFRS completely because of the diverse animal reservoirs and effects of global warming. Reliable forecasting is useful for the prevention and control of HFRS.Two hybrid models, one composed of nonlinear autoregressive neural network (NARNN and autoregressive integrated moving average (ARIMA the other composed of generalized regression neural network (GRNN and ARIMA were constructed to predict the incidence of HFRS in the future one year. Performances of the two hybrid models were compared with ARIMA model.The ARIMA, ARIMA-NARNN ARIMA-GRNN model fitted and predicted the seasonal fluctuation well. Among the three models, the mean square error (MSE, mean absolute error (MAE and mean absolute percentage error (MAPE of ARIMA-NARNN hybrid model was the lowest both in modeling stage and forecasting stage. As for the ARIMA-GRNN hybrid model, the MSE, MAE and MAPE of modeling performance and the MSE and MAE of forecasting performance were less than the ARIMA model, but the MAPE of forecasting performance did not improve.Developing and applying the ARIMA-NARNN hybrid model is an effective method to make us better understand the epidemic characteristics of HFRS and could be helpful to the prevention and control of HFRS.
Ferroli, Paolo; Caldiroli, Dario; Acerbi, Francesco; Scholtze, Maurizio; Piro, Alfonso; Schiariti, Marco; Orena, Eleonora F; Castiglione, Melina; Broggi, Morgan; Perin, Alessandro; DiMeco, Francesco
2012-11-01
Incident reporting systems are universally recognized as important tools for quality improvement in all complex adaptive systems, including the operating room. Nevertheless, introducing a safety culture among neurosurgeons is a slow process, and few studies are available in the literature regarding the implementation of an incident reporting system within a neurosurgical department. The authors describe the institution of an aviation model of incident reporting and investigation in neurosurgery, focusing on the method they have used and presenting some preliminary results. In 2010, the Inpatient Safety On-Board project was developed through cooperation between a team of human factor and safety specialists with aviation backgrounds (DgSky team) and the general manager of the Fondazione Istituto Neurologico Carlo Besta. In 2011, after specific training in safety culture, the authors implemented an aviation-derived prototype of incident reporting within the Department of Neurosurgery. They then developed an experimental protocol to track, analyze, and categorize any near misses that happened in the operating room. This project officially started in January 2012, when a dedicated team of assessors was established. All members of the neurosurgical department were asked to report near misses on a voluntary, confidential, and protected form (Patient Incident Reporting System form, Besta Safety Management Programme). Reports were entered into an online database and analyzed by a dedicated team of assessors with the help of a facilitator, and an aviation-derived root cause analysis was performed. Since January 2012, 14 near misses were analyzed and classified. The near-miss contributing factors were mainly related to human factors (9 of 14 cases), technology (1 of 14 cases), organizational factors (3 of 14 cases), or procedural factors (1 of 14 cases). Implementing an incident reporting system is quite demanding; the process should involve all of the people who work within
Souliès, Antoine; Legrand, Jack; Marec, Hélène; Pruvost, Jérémy; Castelain, Cathy; Burghelea, Teodor; Cornet, Jean-François
2016-03-01
An in-depth investigation of how various illumination conditions influence microalgal growth in photobioreactors (PBR) has been presented. Effects of both the light emission spectrum (white and red) and the light incident angle (0° and 60°) on the PBR surface were investigated. The experiments were conducted in two fully controlled lab-scale PBRs, a torus PBR and a thin flat-panel PBR for high cell density culture. The results obtained in the torus PBR were used to build the kinetic growth model of Chlorella vulgaris taken as a model species. The PBR model was then applied to the thin flat-panel PBR, which was run with various illumination conditions. Its detailed representation of local rate of photon absorption under various conditions (spectral calculation of light attenuation, incident angle influence) enabled the model to take into account all the tested conditions with no further adjustment. This allowed a detailed investigation of the coupling between radiation field and photosynthetic growth. Effects of all the radiation conditions together with pigment acclimation, which was found to be relevant, were investigated in depth. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:247-261, 2016. © 2016 American Institute of Chemical Engineers.
Functional Validation of Heteromeric Kainate Receptor Models.
Paramo, Teresa; Brown, Patricia M G E; Musgaard, Maria; Bowie, Derek; Biggin, Philip C
2017-11-21
Kainate receptors require the presence of external ions for gating. Most work thus far has been performed on homomeric GluK2 but, in vivo, kainate receptors are likely heterotetramers. Agonists bind to the ligand-binding domain (LBD) which is arranged as a dimer of dimers as exemplified in homomeric structures, but no high-resolution structure currently exists of heteromeric kainate receptors. In a full-length heterotetramer, the LBDs could potentially be arranged either as a GluK2 homomer alongside a GluK5 homomer or as two GluK2/K5 heterodimers. We have constructed models of the LBD dimers based on the GluK2 LBD crystal structures and investigated their stability with molecular dynamics simulations. We have then used the models to make predictions about the functional behavior of the full-length GluK2/K5 receptor, which we confirmed via electrophysiological recordings. A key prediction and observation is that lithium ions bind to the dimer interface of GluK2/K5 heteromers and slow their desensitization. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Li Shun; Zhang Sijiong
2014-01-01
A numerical model is presented to simulate the influence function of deformable mirror actuators. The numerical model is formed by Bessel Fourier orthogonal functions, which are constituted of Bessel orthogonal functions and a Fourier basis. A detailed comparison is presented between the new Bessel Fourier model, the Zernike model, the Gaussian influence function and the modified Gaussian influence function. Numerical experiments indicate that the new numerical model is easy to use and more accurate compared with other numerical models. The new numerical model can be used for describing deformable mirror performances and numerical simulations of adaptive optics systems. (research papers)
International Nuclear Information System (INIS)
Howard, Michelle
2013-01-01
ABSTRACT: Burnout and compassion fatigue (CF) adversely affect medical professionals, including those employed in radiation oncology. Previously conducted research acknowledged the presence of burnout in populations of radiation therapists, radiation oncologists, and oncology nursing staff. The aim of the following research was to measure the incidence of burnout or CF in the specific population of medical dosimetrists surveyed. As professional members of the radiation oncology team, this group had not been included in published research data to date. The hypothesis of the subsequent study stated that a comparable incidence of burnout would be observed among medical dosimetrists as had been reported by earlier researchers for a population of radiation therapists. A survey tool based on the Maslach Burnout Inventory (MBI) and distributed to full members of the American Association of Medical Dosimetrists (AAMD) was utilized as the research measurement method. Results obtained indicated an incidence rates of burnout or CF for medical dosimetrists were less than the rates previously measured for radiation therapists (53% vs 11% for emotional exhaustion [EE] and 45% vs 27% for depersonalization [DP]). The incidence of burnout was based on the Burnout Inventory (BI) developed for the research project. Each of the subscales, EE, DP, and decreased personal accomplishment (PA), was considered and analyzed independently. Although not as prevalent among medical dosimetrists as a variety of additional radiation oncology professionals, a significant portion of the population demonstrated signs of burnout or CF. Future concerns abound for the population of medical dosimetrists as a large number of members scored positive for intermediate risk of burnout and CF. Additionally, a large portion of the population was found to be rapidly approaching retirement
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Howard, Michelle, E-mail: Mhoward24601@yahoo.com [University of Wisconsin—La Crosse, WI 54601 (United States)
2013-04-01
ABSTRACT: Burnout and compassion fatigue (CF) adversely affect medical professionals, including those employed in radiation oncology. Previously conducted research acknowledged the presence of burnout in populations of radiation therapists, radiation oncologists, and oncology nursing staff. The aim of the following research was to measure the incidence of burnout or CF in the specific population of medical dosimetrists surveyed. As professional members of the radiation oncology team, this group had not been included in published research data to date. The hypothesis of the subsequent study stated that a comparable incidence of burnout would be observed among medical dosimetrists as had been reported by earlier researchers for a population of radiation therapists. A survey tool based on the Maslach Burnout Inventory (MBI) and distributed to full members of the American Association of Medical Dosimetrists (AAMD) was utilized as the research measurement method. Results obtained indicated an incidence rates of burnout or CF for medical dosimetrists were less than the rates previously measured for radiation therapists (53% vs 11% for emotional exhaustion [EE] and 45% vs 27% for depersonalization [DP]). The incidence of burnout was based on the Burnout Inventory (BI) developed for the research project. Each of the subscales, EE, DP, and decreased personal accomplishment (PA), was considered and analyzed independently. Although not as prevalent among medical dosimetrists as a variety of additional radiation oncology professionals, a significant portion of the population demonstrated signs of burnout or CF. Future concerns abound for the population of medical dosimetrists as a large number of members scored positive for intermediate risk of burnout and CF. Additionally, a large portion of the population was found to be rapidly approaching retirement.
Directory of Open Access Journals (Sweden)
Maayken Elizabeth Louise van den Berg
2017-01-01
Full Text Available Purpose. Understanding the presentation of spinal cord injury (SCI due to tumours considering population distribution and temporal trends is key to managing SCI health services. This study quantified incidence rates, function scores, and trends of SCI due to tumour or metastasis over an 18-year time period in a defined region in Spain. Methods. A retrospective cohort study included in-and outpatients with nontraumatic SCI due to tumour or metastasis admitted to a metropolitan hospital in Spain between 1991 and 2008. Main outcome measures were crude and age- and sex-adjusted incidence rates, tumour location and type, distribution by spinal level, neurological level of injury, and impairment ASIA scores. Results. Primary tumour or metastasis accounted for 32.5% of nontraumatic SCI with an incidence rate of 4.1 per million population. Increasing rates with age and over time were observed. Major pathology groups were intradural-extramedullary masses from which meningiomas and neurinomas accounted for 40%. Lesions were mostly incomplete with predominant ASIA Grade D. Conclusions. Increasing incidence rates of tumour-related SCI over time in the middle-aged and the elderly suggest a growing need for neurooncology health resources in the future.
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Játékos, Balázs, E-mail: jatekosb@eik.bme.hu; Ujhelyi, Ferenc; Lőrincz, Emőke; Erdei, Gábor
2015-01-01
SPADnet-I is a prototype, fully digital, high spatial and temporal resolution silicon photon counter, based on standard CMOS imaging technology, developed by the SPADnet consortium. Being a novel device, the exact dependence of photon detection probability (PDP) of SPADnet-I was not known as a function of angle of incidence, wavelength and polarization of the incident light. Our targeted application area of this sensor is next generation PET detector modules, where they will be used along with LYSO:Ce scintillators. Hence, we performed an extended investigation of PDP in a wide range of angle of incidence (0° to 80°), concentrating onto a 60 nm broad wavelength interval around the characteristic emission peak (λ=420 nm) of the scintillator. In the case where the sensor was optically coupled to a scintillator, our experiments showed a notable dependence of PDP on angle, polarization and wavelength. The sensor has an average PDP of approximately 30% from 0° to 60° angle of incidence, where it starts to drop rapidly. The PDP turned out not to be polarization dependent below 30°. If the sensor is used without a scintillator (i.e. the light source is in air), the polarization dependence is much less expressed, it begins only from 50°.
Shin, Yung C.; Bailey, Neil; Katinas, Christopher; Tan, Wenda
2018-01-01
This paper presents an overview of vertically integrated comprehensive predictive modeling capabilities for directed energy deposition processes, which have been developed at Purdue University. The overall predictive models consist of vertically integrated several modules, including powder flow model, molten pool model, microstructure prediction model and residual stress model, which can be used for predicting mechanical properties of additively manufactured parts by directed energy deposition processes with blown powder as well as other additive manufacturing processes. Critical governing equations of each model and how various modules are connected are illustrated. Various illustrative results along with corresponding experimental validation results are presented to illustrate the capabilities and fidelity of the models. The good correlations with experimental results prove the integrated models can be used to design the metal additive manufacturing processes and predict the resultant microstructure and mechanical properties.
Shin, Yung C.; Bailey, Neil; Katinas, Christopher; Tan, Wenda
2018-05-01
This paper presents an overview of vertically integrated comprehensive predictive modeling capabilities for directed energy deposition processes, which have been developed at Purdue University. The overall predictive models consist of vertically integrated several modules, including powder flow model, molten pool model, microstructure prediction model and residual stress model, which can be used for predicting mechanical properties of additively manufactured parts by directed energy deposition processes with blown powder as well as other additive manufacturing processes. Critical governing equations of each model and how various modules are connected are illustrated. Various illustrative results along with corresponding experimental validation results are presented to illustrate the capabilities and fidelity of the models. The good correlations with experimental results prove the integrated models can be used to design the metal additive manufacturing processes and predict the resultant microstructure and mechanical properties.
Seddon, Johanna M; Reynolds, Robyn; Maller, Julian; Fagerness, Jesen A; Daly, Mark J; Rosner, Bernard
2009-05-01
The joint effects of genetic, ocular, and environmental variables were evaluated and predictive models for prevalence and incidence of AMD were assessed. Participants in the multicenter Age-Related Eye Disease Study (AREDS) were included in a prospective evaluation of 1446 individuals, of which 279 progressed to advanced AMD (geographic atrophy or neovascular disease) and 1167 did not progress during 6.3 years of follow-up. For prevalent AMD, 509 advanced cases were compared with 222 controls. Covariates for the incidence analysis included age, sex, education, smoking, body mass index (BMI), baseline AMD grade, and the AREDS vitamin-mineral treatment assignment. DNA specimens were evaluated for six variants in five genes related to AMD. Unconditional logistic regression analyses were performed for prevalent and incident advanced AMD. An algorithm was developed and receiver operating characteristic curves and C statistics were calculated to assess the predictive ability of risk scores to discriminate progressors from nonprogressors. All genetic polymorphisms were independently related to prevalence of advanced AMD, controlling for genetic factors, smoking, BMI, and AREDS treatment. Multivariate odds ratios (ORs) were 3.5 (95% confidence interval [CI], 1.7-7.1) for CFH Y402H; 3.7 (95% CI, 1.6-8.4) for CFH rs1410996; 25.4 (95% CI, 8.6-75.1) for LOC387715 A69S (ARMS2); 0.3 (95% CI, 0.1-0.7) for C2 E318D; 0.3 (95% CI, 0.1-0.5) for CFB; and 3.6 (95% CI, 1.4-9.4) for C3 R102G, comparing the homozygous risk/protective genotypes to the referent genotypes. For incident AMD, all these variants except CFB were significantly related to progression to advanced AMD, after controlling for baseline AMD grade and other factors, with ORs from 1.8 to 4.0 for presence of two risk alleles and 0.4 for the protective allele. An interaction was seen between CFH402H and treatment, after controlling for all genotypes. Smoking was independently related to AMD, with a multiplicative joint
Field assessment of a model tuberculosis outbreak response plan for low-incidence areas
Directory of Open Access Journals (Sweden)
Pascopella Lisa
2007-10-01
Full Text Available Abstract Background For a regional project in four low-incidence states, we designed a customizable tuberculosis outbreak response plan. Prior to dissemination of the plan, a tuberculosis outbreak occurred, presenting an opportunity to perform a field assessment of the plan. The purpose of the assessment was to ensure that the plan included essential elements to help public health professionals recognize and respond to outbreaks. Methods We designed a semi-structured questionnaire and interviewed all key stakeholders involved in the response. We used common themes to assess validity of and identify gaps in the plan. A subset of participants provided structured feedback on the plan. Results We interviewed 11 public health and six community stakeholders. The assessment demonstrated that (1 almost all of the main response activities were reflected in the plan; (2 the plan added value by providing a definition of a tuberculosis outbreak and guidelines for communication and evaluation. These were areas that lacked written protocols during the actual outbreak response; and (3 basic education about tuberculosis and the interpretation and use of genotyping data were important needs. Stakeholders also suggested adding to the plan questions for evaluation and a section for specific steps to take when an outbreak is suspected. Conclusion An interactive field assessment of a programmatic tool revealed the value of a systematic outbreak response plan with a standard definition of a tuberculosis outbreak, guidelines for communication and evaluation, and response steps. The assessment highlighted the importance of education and training for tuberculosis in low-incidence areas.
Control functions in nonseparable simultaneous equations models
Blundell, R.; Matzkin, R. L.
2014-01-01
The control function approach (Heckman and Robb (1985)) in a system of linear simultaneous equations provides a convenient procedure to estimate one of the functions in the system using reduced form residuals from the other functions as additional regressors. The conditions on the structural system under which this procedure can be used in nonlinear and nonparametric simultaneous equations has thus far been unknown. In this paper, we define a new property of functions called control function ...
Function modeling: improved raster analysis through delayed reading and function raster datasets
John S. Hogland; Nathaniel M. Anderson; J .Greg Jones
2013-01-01
Raster modeling is an integral component of spatial analysis. However, conventional raster modeling techniques can require a substantial amount of processing time and storage space, often limiting the types of analyses that can be performed. To address this issue, we have developed Function Modeling. Function Modeling is a new modeling framework that streamlines the...
Breast cancer risk in atomic bomb survivors from multi-model inference with incidence data 1958-1998
International Nuclear Information System (INIS)
Kaiser, J.C.; Jacob, P.; Meckbach, R.; Cullings, H.M.
2012-01-01
Breast cancer risk from radiation exposure has been analyzed in the cohort of Japanese a-bomb survivors using empirical models and mechanistic two-step clonal expansion (TSCE) models with incidence data from 1958 to 1998. TSCE models rely on a phenomenological representation of cell transition processes on the path to cancer. They describe the data as good as empirical models and this fact has been exploited for risk assessment. Adequate models of both types have been selected with a statistical protocol based on parsimonious parameter deployment and their risk estimates have been combined using multi-model inference techniques. TSCE models relate the radiation risk to cell processes which are controlled by age-increasing rates of initiating mutations and by changes in hormone levels due to menopause. For exposure at young age, they predict an enhanced excess relative risk (ERR) whereas the preferred empirical model shows no dependence on age at exposure. At attained age 70, the multi-model median of the ERR at 1 Gy decreases moderately from 1.2 Gy"-"1 (90% CI 0.72; 2.1) for exposure at age 25 to a 30% lower value for exposure at age 55. For cohort strata with few cases, where model predictions diverge, uncertainty intervals from multi-model inference are enhanced by up to a factor of 1.6 compared to the preferred empirical model. Multi-model inference provides a joint risk estimate from several plausible models rather than relying on a single model of choice. It produces more reliable point estimates and improves the characterization of uncertainties. The method is recommended for risk assessment in practical radiation protection. (orig.)
Breast cancer risk in atomic bomb survivors from multi-model inference with incidence data 1958-1998
Energy Technology Data Exchange (ETDEWEB)
Kaiser, J.C.; Jacob, P.; Meckbach, R. [Institute of Radiation Protection, Helmholtz-Zentrum Muenchen, German Research Centre for Environmental Health, Neuherberg (Germany); Cullings, H.M. [Radiation Effects Research Foundation, Department of Statistics, Hiroshima (Japan)
2012-03-15
Breast cancer risk from radiation exposure has been analyzed in the cohort of Japanese a-bomb survivors using empirical models and mechanistic two-step clonal expansion (TSCE) models with incidence data from 1958 to 1998. TSCE models rely on a phenomenological representation of cell transition processes on the path to cancer. They describe the data as good as empirical models and this fact has been exploited for risk assessment. Adequate models of both types have been selected with a statistical protocol based on parsimonious parameter deployment and their risk estimates have been combined using multi-model inference techniques. TSCE models relate the radiation risk to cell processes which are controlled by age-increasing rates of initiating mutations and by changes in hormone levels due to menopause. For exposure at young age, they predict an enhanced excess relative risk (ERR) whereas the preferred empirical model shows no dependence on age at exposure. At attained age 70, the multi-model median of the ERR at 1 Gy decreases moderately from 1.2 Gy{sup -1} (90% CI 0.72; 2.1) for exposure at age 25 to a 30% lower value for exposure at age 55. For cohort strata with few cases, where model predictions diverge, uncertainty intervals from multi-model inference are enhanced by up to a factor of 1.6 compared to the preferred empirical model. Multi-model inference provides a joint risk estimate from several plausible models rather than relying on a single model of choice. It produces more reliable point estimates and improves the characterization of uncertainties. The method is recommended for risk assessment in practical radiation protection. (orig.)
Dynamical analysis of cigarette smoking model with a saturated incidence rate
Zeb, Anwar; Bano, Ayesha; Alzahrani, Ebraheem; Zaman, Gul
2018-04-01
In this paper, we consider a delayed smoking model in which the potential smokers are assumed to satisfy the logistic equation. We discuss the dynamical behavior of our proposed model in the form of Delayed Differential Equations (DDEs) and show conditions for asymptotic stability of the model in steady state. We also discuss the Hopf bifurcation analysis of considered model. Finally, we use the nonstandard finite difference (NSFD) scheme to show the results graphically with help of MATLAB.
Spaeder, M C; Fackler, J C
2012-04-01
Respiratory syncytial virus (RSV) is the most common cause of documented viral respiratory infections, and the leading cause of hospitalization, in young children. We performed a retrospective time-series analysis of all patients aged Forecasting models of weekly RSV incidence for the local community, inpatient paediatric hospital and paediatric intensive-care unit (PICU) were created. Ninety-five percent confidence intervals calculated around our models' 2-week forecasts were accurate to ±9·3, ±7·5 and ±1·5 cases/week for the local community, inpatient hospital and PICU, respectively. Our results suggest that time-series models may be useful tools in forecasting the burden of RSV infection at the local and institutional levels, helping communities and institutions to optimize distribution of resources based on the changing burden and severity of illness in their respective communities.
Driscoll, Andrea; Barnes, Elizabeth H; Blankenberg, Stefan; Colquhoun, David M; Hunt, David; Nestel, Paul J; Stewart, Ralph A; West, Malcolm J; White, Harvey D; Simes, John; Tonkin, Andrew
2017-12-01
Coronary heart disease is a major cause of heart failure. Availability of risk-prediction models that include both clinical parameters and biomarkers is limited. We aimed to develop such a model for prediction of incident heart failure. A multivariable risk-factor model was developed for prediction of first occurrence of heart failure death or hospitalization. A simplified risk score was derived that enabled subjects to be grouped into categories of 5-year risk varying from 20%. Among 7101 patients from the LIPID study (84% male), with median age 61years (interquartile range 55-67years), 558 (8%) died or were hospitalized because of heart failure. Older age, history of claudication or diabetes mellitus, body mass index>30kg/m 2 , LDL-cholesterol >2.5mmol/L, heart rate>70 beats/min, white blood cell count, and the nature of the qualifying acute coronary syndrome (myocardial infarction or unstable angina) were associated with an increase in heart failure events. Coronary revascularization was associated with a lower event rate. Incident heart failure increased with higher concentrations of B-type natriuretic peptide >50ng/L, cystatin C>0.93nmol/L, D-dimer >273nmol/L, high-sensitivity C-reactive protein >4.8nmol/L, and sensitive troponin I>0.018μg/L. Addition of biomarkers to the clinical risk model improved the model's C statistic from 0.73 to 0.77. The net reclassification improvement incorporating biomarkers into the clinical model using categories of 5-year risk was 23%. Adding a multibiomarker panel to conventional parameters markedly improved discrimination and risk classification for future heart failure events. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.
Mirror neurons: functions, mechanisms and models.
Oztop, Erhan; Kawato, Mitsuo; Arbib, Michael A
2013-04-12
Mirror neurons for manipulation fire both when the animal manipulates an object in a specific way and when it sees another animal (or the experimenter) perform an action that is more or less similar. Such neurons were originally found in macaque monkeys, in the ventral premotor cortex, area F5 and later also in the inferior parietal lobule. Recent neuroimaging data indicate that the adult human brain is endowed with a "mirror neuron system," putatively containing mirror neurons and other neurons, for matching the observation and execution of actions. Mirror neurons may serve action recognition in monkeys as well as humans, whereas their putative role in imitation and language may be realized in human but not in monkey. This article shows the important role of computational models in providing sufficient and causal explanations for the observed phenomena involving mirror systems and the learning processes which form them, and underlines the need for additional circuitry to lift up the monkey mirror neuron circuit to sustain the posited cognitive functions attributed to the human mirror neuron system. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Dongdong Sun
Full Text Available Hypertension is a leading global health threat and a major cardiovascular disease. Since clinical interventions are effective in delaying the disease progression from prehypertension to hypertension, diagnostic prediction models to identify patient populations at high risk for hypertension are imperative.Both PubMed and Embase databases were searched for eligible reports of either prediction models or risk scores of hypertension. The study data were collected, including risk factors, statistic methods, characteristics of study design and participants, performance measurement, etc.From the searched literature, 26 studies reporting 48 prediction models were selected. Among them, 20 reports studied the established models using traditional risk factors, such as body mass index (BMI, age, smoking, blood pressure (BP level, parental history of hypertension, and biochemical factors, whereas 6 reports used genetic risk score (GRS as the prediction factor. AUC ranged from 0.64 to 0.97, and C-statistic ranged from 60% to 90%.The traditional models are still the predominant risk prediction models for hypertension, but recently, more models have begun to incorporate genetic factors as part of their model predictors. However, these genetic predictors need to be well selected. The current reported models have acceptable to good discrimination and calibration ability, but whether the models can be applied in clinical practice still needs more validation and adjustment.
Van Eck, D.
2009-01-01
In this paper, I discuss a methodology for the conversion of functional models between functional taxonomies developed by Kitamura et al. (2007) and Ookubo et al. (2007). They apply their methodology to the conversion of functional models described in terms of the Functional Basis taxonomy into
School Teams up for SSP Functional Models
Pignolet, G.; Lallemand, R.; Celeste, A.; von Muldau, H.
2002-01-01
Space Solar Power systems appear increasingly as one of the major solutions to the upcoming global energy crisis, by collecting solar energy in space where this is most easy, and sending it by microwave beam to the surface of the planet, where the need for controlled energy is located. While fully operational systems are still decades away, the need for major development efforts is with us now. Yet, for many decision-makers and for most of the public, SSP often still sounds like science fiction. Six functional demonstration systems, based on the Japanese SPS-2000 concept, have been built as a result of a cooperation between France and Japan, and they are currently used extensively, in Japan, in Europe and in North America, for executive presentations as well as for public exhibitions. There is demand for more models, both for science museums and for use by energy dedicated groups, and a senior high school in La Reunion, France, has picked up the challenge to make the production of such models an integrated practical school project for pre-college students. In December 2001, the administration and the teachers of the school have evaluated the feasibility of the project and eventually taken the go decision for the school year 2002- 2003, when for education purposes a temporary "school business company" will be incorporated with the goal to study and manufacture a limited series of professional quality SSP demonstration models, and to sell them world- wide to institutions and advocacy groups concerned with energy problems and with the environment. The different sections of the school will act as the different services of an integrated business : based on the current existing models, the electronic section will redesign the energy management system and the microwave projector module, while the mechanical section of the school will adapt and re-conceive the whole packaging of the demonstrator. The French and foreign language sections will write up a technical manual for
Directory of Open Access Journals (Sweden)
Ljubenov Vladan L.
2014-01-01
Full Text Available In this paper we present the results of calculations and analyses of the integral particle reflection coefficient of photons for oblique photon incidence on planar targets, in the domain of initial photon energies from 100 keV to 300 keV. The results are based on the Monte Carlo simulations of the photon reflection from water, concrete, aluminum, iron, and copper materials, performed by the MCNP code. It has been observed that the integral particle reflection coefficient as a function of the ratio of total cross-section of photons and effective atomic number of target material shows universal behavior for all the analyzed shielding materials in the selected energy domain. Analytical formulas for different angles of photon incidence have been proposed, which describe the reflection of photons for all the materials and energies analyzed.
International Nuclear Information System (INIS)
Ramos, M; Ferrer, S; Villaescusa, J I; Verdu, G; Salas, M D; Cuevas, M D
2005-01-01
The authors report on a method to calculate radiological risks, applicable to breast screening programs and other controlled medical exposures to ionizing radiation. In particular, it has been applied to make a risk assessment in the Valencian Breast Cancer Early Detection Program (VBCEDP) in Spain. This method is based on a parametric approach, through Markov processes, of hazard functions for radio-induced breast cancer incidence and mortality, with mean glandular breast dose, attained age and age-at-exposure as covariates. Excess relative risk functions of breast cancer mortality have been obtained from two different case-control studies exposed to ionizing radiation, with different follow-up time: the Canadian Fluoroscopy Cohort Study (1950-1987) and the Life Span Study (1950-1985 and 1950-1990), whereas relative risk functions for incidence have been obtained from the Life Span Study (1958-1993), the Massachusetts tuberculosis cohorts (1926-1985 and 1970-1985), the New York post-partum mastitis patients (1930-1981) and the Swedish benign breast disease cohort (1958-1987). Relative risks from these cohorts have been transported to the target population undergoing screening in the Valencian Community, a region in Spain with about four and a half million inhabitants. The SCREENRISK software has been developed to estimate radiological detriments in breast screening. Some hypotheses corresponding to different screening conditions have been considered in order to estimate the total risk associated with a woman who takes part in all screening rounds. In the case of the VBCEDP, the total radio-induced risk probability for fatal breast cancer is in a range between [5 x 10 -6 , 6 x 10 -4 ] versus the natural rate of dying from breast cancer in the Valencian Community which is 9.2 x 10 -3 . The results show that these indicators could be included in quality control tests and could be adequate for making comparisons between several screening programs
Cyber Incidents Involving Control Systems
Energy Technology Data Exchange (ETDEWEB)
Robert J. Turk
2005-10-01
The Analysis Function of the US-CERT Control Systems Security Center (CSSC) at the Idaho National Laboratory (INL) has prepared this report to document cyber security incidents for use by the CSSC. The description and analysis of incidents reported herein support three CSSC tasks: establishing a business case; increasing security awareness and private and corporate participation related to enhanced cyber security of control systems; and providing informational material to support model development and prioritize activities for CSSC. The stated mission of CSSC is to reduce vulnerability of critical infrastructure to cyber attack on control systems. As stated in the Incident Management Tool Requirements (August 2005) ''Vulnerability reduction is promoted by risk analysis that tracks actual risk, emphasizes high risk, determines risk reduction as a function of countermeasures, tracks increase of risk due to external influence, and measures success of the vulnerability reduction program''. Process control and Supervisory Control and Data Acquisition (SCADA) systems, with their reliance on proprietary networks and hardware, have long been considered immune to the network attacks that have wreaked so much havoc on corporate information systems. New research indicates this confidence is misplaced--the move to open standards such as Ethernet, Transmission Control Protocol/Internet Protocol, and Web technologies is allowing hackers to take advantage of the control industry's unawareness. Much of the available information about cyber incidents represents a characterization as opposed to an analysis of events. The lack of good analyses reflects an overall weakness in reporting requirements as well as the fact that to date there have been very few serious cyber attacks on control systems. Most companies prefer not to share cyber attack incident data because of potential financial repercussions. Uniform reporting requirements will do much to make this
Miller, Ronald L.; McPherson, Benjamin F.
1995-04-01
Field studies that compare the spatial and temporal variation in light attenuation often neglect effects of solar elevation angle, yet these effects can be significant. To approximately correct for these angular effects, we developed a model that uses a simplified geometric description of incident direct solar beam and diffuse skylight. The model incorporates effects of solar elevation angle and cloudiness on the amount of in-air photosynthetically active radiation (PAR) that passes through the air-water interface and on K0in waters of relatively low turbidity. The model was calibrated with 3266 5-min averages of scalar PAR measured in air and at two depths in water and permits the value of K0to be adjusted approximately for the effects of time of day, season and cloudiness. The model was then used with 255 days of in-air PAR data (15-min averages) to evaluate irradiance that entered the water and attenuation in the water. On an annual basis, 49% of the incident scalar irradiance, or 380 μmol m -2s -1, was estimated to enter the water of Tampa Bay. The value of K0was estimated to vary as much as 41% on a clear summer day due to changes in solar elevation angle. The model was used to make estimates of the depth to which sea-grasses might receive adequate light for survival for a range of values of K0. This approach should be useful for projecting the effect of changes in water clarity on the depth of sea-grass survival and for comparing values of K0collected at different times of day and in different seasons.
Eaton, Lisa A.; Kalichman, Seth C.; Kenny, David A.; Harel, Ofer
2013-01-01
Background Project EXPLORE -- a large-scale, behavioral intervention tested among men who have sex with men (MSM) at-risk for HIV infection --was generally deemed as ineffective in reducing HIV incidence. Using novel and more precise data analytic techniques we reanalyzed Project EXPLORE by including both direct and indirect paths of intervention effects. Methods Data from 4,296 HIV negative MSM who participated in Project EXPLORE, which included ten sessions of behavioral risk reduction counseling completed from 1999-2005, were included in the analysis. We reanalyzed the data to include parameters that estimate the overtime effects of the intervention on unprotected anal sex and the over-time effects of the intervention on HIV status mediated by unprotected anal sex simultaneously in a single model. Results We found the indirect effect of intervention on HIV infection through unprotected anal sex to be statistically significant up through 12 months post-intervention, OR=.83, 95% CI=.72-.95. Furthermore, the intervention significantly reduced unprotected anal sex up through 18 months post-intervention, OR=.79, 95% CI=.63-.99. Discussion Our results reveal effects not tested in the original model that offer new insight into the effectiveness of a behavioral intervention for reducing HIV incidence. Project EXPLORE demonstrated that when tested against an evidence-based, effective control condition can result in reductions in rates of HIV acquisition at one year follow-up. Findings highlight the critical role of addressing behavioral risk reduction counseling in HIV prevention. PMID:23245226
Chrysohoou, C; Panagiotakos, D B; Pitsavos, C; Skoumas, J; Toutouza, M; Papaioannou, I; Stefanadis, C
2010-06-01
We aimed to evaluate the association between renal function and various cardiovascular disease (CVD) risk factors, as well as 5-year incidence of CVD, in a sample of CVD free adults. (i) Cross-sectional information from n = 1975. Greek men and women (>18 years) without CVD and hypertension at baseline examination and (ii) 5-year (2001-06) survival data from n = 2101 individuals without CVD at baseline, all participants in the ATTICA study, were analysed in this work. Kidney function was quantified by the baseline estimated creatinine clearance rate (C(cr)), using the Cockcroft-Gault formula and the National Kidney Foundation recommendations. Outcome of interest was the development of CVD that was defined according to WHO-ICD-10 criteria. At baseline, the prevalence of moderate-to-severe renal dysfunction (i.e. C(cr) smoking, hypercholesterolemia and homocysteine levels and greater adherence to the Mediterranean diet were inversely associated with C(cr) rate (P smoking habits (0.89, 0.60-1.32) and physical activity status (0.86, 0.56-1.21). Renal function seems to be associated with the levels of lifestyle and bio-clinical CVD risk factors and contribute to the long-term incidence of cardiac events. Public health care practitioners should take into account renal function in better preventing the burden of CVD at individual, and population level, as well.
Drongelen AW van; Roszek B; Hilbers-Modderman ESM; Kallewaard M; Wassenaar C; LGM
2002-01-01
This RIVM study was performed to gain insight into wheelchair-related incidents with powered and manual wheelchairs reported to the USA FDA, the British MDA and the Dutch Center for Quality and Usability Research of Technical Aids (KBOH). The data in the databases do not indicate that incidents with
Bezemer-Krijnen, Marieke; Wijnant, Ysbrand H.; de Boer, Andries; Glorieux, C.
2015-01-01
Sound absorption of porous asphalt pavements is an important property when reducing tyre-road noise. A hybrid model has been developed to predict the sound absorption of porous roads. This model is a combination of an analytical analysis of the sound eld and a numerical approach, including both the
Modelling absorption in porous asphalt concrete for oblique incident sound waves
Bezemer-Krijnen, Marieke; Wijnant, Ysbrand H.; de Boer, Andries; Sas, P; Moens, D.; Denayer, H.
2014-01-01
A numerical model to predict the sound absorption of porous asphalt has been developed. The approach is a combination between a microstructural approach and a finite element approach. The model used to describe the viscothermal properties of the air inside the pores of the asphalt is the low reduced
CSIR Research Space (South Africa)
Mbecke, ZP
2010-07-01
Full Text Available factors over other contributing factors. The aim of the thesis is three-fold. Firstly, to review theories explaining crime causation in general and child abuse in particular. Secondly to develop the Integrated Modeled Theory as a model that facilitates...
Awad, E M
1999-01-01
In this work, we have studied the effect of the radiation damage caused by the incident particles on the activation energy of etching for CR-39 samples. The damage produced by the incident particle is expressed in terms of the linear energy transfer (LET). CR-39 samples from American Acrylic were irradiated to three different LET particles. These are N (LET sub 2 sub 0 sub 0 = 20 KeV/mu m) as a light particle, Fe (LET sub 2 sub 0 sub 0 = 110 KeV/mu m) as a medium particle and fission fragments (ff) from a sup 2 sup 5 sup 2 Cf source as heavy particles. In general the bulk etch rate was calculated using the weight difference method and the track etch rate was determined using the track geometry at various temperatures (50-90 deg. C) and concentrations (4-9 N) of the NaOH etchant. The average activation energy E sub b related to the bulk etch rate v sub b was calculated from 1n v sub b vs. 1/T. The average activation energy E sub t related to the track etch rate v sub t was estimated from 1n v sub t vs. 1/T. It...
Dynamical analysis and simulation of a 2-dimensional disease model with convex incidence
Yu, Pei; Zhang, Wenjing; Wahl, Lindi M.
2016-08-01
In this paper, a previously developed 2-dimensional disease model is studied, which can be used for both epidemiologic modeling and in-host disease modeling. The main attention of this paper is focused on various dynamical behaviors of the system, including Hopf and generalized Hopf bifurcations which yield bistability and tristability, Bogdanov-Takens bifurcation, and homoclinic bifurcation. It is shown that the Bogdanov-Takens bifurcation and homoclinic bifurcation provide a new mechanism for generating disease recurrence, that is, cycles of remission and relapse such as the viral blips observed in HIV infection.
International Nuclear Information System (INIS)
Kotevski, Darko
2008-01-01
This paper is a resume of the master thesis made within my master studies at the Department for transmission and distribution systems at FEIT-Skopje. New methodology is presented for estimation of the rates of lightning strikes on power lines and substations with Monte Carlo simulation. Modeling is based on well known electro geometric model which states that protection zones of lightning protection devices are dependant with amplitude of the lighting current. Therefore, for a known configuration it is possible with application of simple numerical methods to evaluate efficiency of the protection devices. Data gained from the simulations can be used to design such devices, to correct existing lightning protection systems or to make analysis for improving reliability of power system elements in lightning incidence. (Author)
International Nuclear Information System (INIS)
Kotevski, Darko
2008-01-01
This paper is a resume of the master thesis made within my master studies at the Department for transmission and distribution systems at FEIT-Skopje. New methodology is presented for estimation of the rates of lightning strikes on power lines and substations with Monte Carlo simulation. Modeling is based on well known electro geometric model which states that protection zones of lightning protection devices are dependant with amplitude of the lighting current. Therefore, for a known configuration it is possible with application of simple numerical methods to evaluate efficiency of the protection devices. Data gained from the simulations can be used to design such devices, to correct existing lightning protection systems or to make analysis for improving reliability of power system elements in lightning incidence. (Author
Modelling the dependability in Network Function Virtualisation
Lin, Wenqi
2017-01-01
Network Function Virtualization has been brought up to allow the TSPs to have more possibilities and flexibilities to provision services with better load optimizing, energy utilizing and dynamic scaling. Network functions will be decoupled from the underlying dedicated hardware into software instances that run on commercial off-the-shelf servers. However, the development is still at an early stage and the dependability concerns raise by the virtualization of the network functions are touched ...
Hapugoda, J. C.; Sooriyarachchi, M. R.
2017-09-01
Survival time of patients with a disease and the incidence of that particular disease (count) is frequently observed in medical studies with the data of a clustered nature. In many cases, though, the survival times and the count can be correlated in a way that, diseases that occur rarely could have shorter survival times or vice versa. Due to this fact, joint modelling of these two variables will provide interesting and certainly improved results than modelling these separately. Authors have previously proposed a methodology using Generalized Linear Mixed Models (GLMM) by joining the Discrete Time Hazard model with the Poisson Regression model to jointly model survival and count model. As Aritificial Neural Network (ANN) has become a most powerful computational tool to model complex non-linear systems, it was proposed to develop a new joint model of survival and count of Dengue patients of Sri Lanka by using that approach. Thus, the objective of this study is to develop a model using ANN approach and compare the results with the previously developed GLMM model. As the response variables are continuous in nature, Generalized Regression Neural Network (GRNN) approach was adopted to model the data. To compare the model fit, measures such as root mean square error (RMSE), absolute mean error (AME) and correlation coefficient (R) were used. The measures indicate the GRNN model fits the data better than the GLMM model.
Variance Function Partially Linear Single-Index Models1.
Lian, Heng; Liang, Hua; Carroll, Raymond J
2015-01-01
We consider heteroscedastic regression models where the mean function is a partially linear single index model and the variance function depends upon a generalized partially linear single index model. We do not insist that the variance function depend only upon the mean function, as happens in the classical generalized partially linear single index model. We develop efficient and practical estimation methods for the variance function and for the mean function. Asymptotic theory for the parametric and nonparametric parts of the model is developed. Simulations illustrate the results. An empirical example involving ozone levels is used to further illustrate the results, and is shown to be a case where the variance function does not depend upon the mean function.
International Nuclear Information System (INIS)
Tinger, Alfred; Wasserman, Todd H.; Klein, Eric E.; Miller, Elizabeth A.; Roberts, Tracy; Piephoff, James V.; Kucik, Nancy A.
1997-01-01
Purpose: There is an increased incidence of breast cancer following mantle field radiation therapy for Hodgkin's disease (HD). We reviewed the experience at the Mallinckrodt Institute of Radiology (MIR) for radiation factors related to the development of breast cancer after mantle field radiation therapy for HD. Methods: The radiation therapy records of 152 women treated with mantle field irradiation for HD at MIR between 1966-1985 were reviewed for the development of breast cancer and treatment-related factors. All patients had a minimum of 5 years of follow-up. The treatment era (1966-1974 vs. 1975-1985), stage of HD, mediastinal dose, axillary dose, maximum dose from the anterior field (anterior d max dose), the anterior-posterior:posterior-anterior (AP:PA) ratio, age at the time of treatment, length of follow-up, and history of splenectomy were analyzed as possible contributing factors for the development of breast cancer. The observed number of breast cancers was compared to the expected number based on age-adjusted incidences from the Connecticut Tumor Registry. Results: Ten breast cancers occurred in the population. Eight involved an upper outer quadrant. In a multivariate analysis, the development of breast cancer was significantly associated with axillary dose. Patients in the early treatment era were at an increased risk for the development of breast cancer due to high anterior d max and breast doses from weighting the fields anteriorly on a low energy linear accelerator. The use of current radiation therapy techniques was not related to an increased risk of breast cancer with a median follow-up of 13 years. Conclusions: A high dose to the axilla and the anterior d max point is significantly associated with the development of breast cancer after mantle field irradiation for HD. Efforts to protect the breast from high doses will likely lessen the increased risk of breast cancer in women treated with radiation therapy for HD
Novel, high incidence exercise-induced muscle bleeding model in hemophilia B mice
DEFF Research Database (Denmark)
Tranholm, M.; Kristensen, Annemarie Thuri; Broberg, M. L.
2015-01-01
INTRODUCTION: Muscle hematomas are the second most common complication of hemophilia and insufficient treatment may result in serious and even life-threatening complications. Hemophilic dogs and rats do experience spontaneous muscle bleeding, but currently, no experimental animal model is available...... specifically investigating spontaneous muscle bleeds in a hemophilic setting. AIM: The objective of this study was to develop a model of spontaneous muscle bleeds in hemophilia B mice. We hypothesized that treadmill exercise would induce muscle bleeds in hemophilia B mice but not in normal non-hemophilic mice...... and that treatment with recombinant factor IX (rFIX) before treadmill exercise could prevent the occurrence of pathology. METHODS: A total of 203 mice (123 F9-KO and 80 C57BL/6NTac) were included in three separate studies: (i) the model implementation study investigating the bleeding pattern in hemophilia B mice...
2010-03-01
Urban transportation networks, consisting of numerous links and nodes, experience traffic incidents such as accidents and road maintenance work. A typical consequence of incidents is congestion which results in long queues and causes high travel time...
2010-03-01
Urban transportation networks, consisting of numerous links and nodes, experience traffic incidents such as accidents and road : maintenance work. A typical consequence of incidents is congestion which results in long queues and causes high travel ti...
Validation of aerodynamic parameters at high angles of attack for RAE high incidence research models
Ross, A. Jean; Edwards, Geraldine F.; Klein, Vladislav; Batterson, James G.
1987-01-01
Two series of free-flight tests have been conducted for combat aircraft configuration research models in order to investigate flight behavior near departure conditions as well as to obtain response data from which aerodynamic characteristics can be derived. The structure of the mathematical model and values for the mathematical derivatives have been obtained through an analysis of the first series, using stepwise regression. The results thus obtained are the bases of the design of active control laws. Flight test results for a novel configuration are compared with predicted responses.
Factorisations for partition functions of random Hermitian matrix models
International Nuclear Information System (INIS)
Jackson, D.M.; Visentin, T.I.
1996-01-01
The partition function Z N , for Hermitian-complex matrix models can be expressed as an explicit integral over R N , where N is a positive integer. Such an integral also occurs in connection with random surfaces and models of two dimensional quantum gravity. We show that Z N can be expressed as the product of two partition functions, evaluated at translated arguments, for another model, giving an explicit connection between the two models. We also give an alternative computation of the partition function for the φ 4 -model.The approach is an algebraic one and holds for the functions regarded as formal power series in the appropriate ring. (orig.)
Meads, Catherine; Ahmed, Ikhlaaq; Riley, Richard D
2012-04-01
A risk prediction model is a statistical tool for estimating the probability that a currently healthy individual with specific risk factors will develop a condition in the future such as breast cancer. Reliably accurate prediction models can inform future disease burdens, health policies and individual decisions. Breast cancer prediction models containing modifiable risk factors, such as alcohol consumption, BMI or weight, condom use, exogenous hormone use and physical activity, are of particular interest to women who might be considering how to reduce their risk of breast cancer and clinicians developing health policies to reduce population incidence rates. We performed a systematic review to identify and evaluate the performance of prediction models for breast cancer that contain modifiable factors. A protocol was developed and a sensitive search in databases including MEDLINE and EMBASE was conducted in June 2010. Extensive use was made of reference lists. Included were any articles proposing or validating a breast cancer prediction model in a general female population, with no language restrictions. Duplicate data extraction and quality assessment were conducted. Results were summarised qualitatively, and where possible meta-analysis of model performance statistics was undertaken. The systematic review found 17 breast cancer models, each containing a different but often overlapping set of modifiable and other risk factors, combined with an estimated baseline risk that was also often different. Quality of reporting was generally poor, with characteristics of included participants and fitted model results often missing. Only four models received independent validation in external data, most notably the 'Gail 2' model with 12 validations. None of the models demonstrated consistently outstanding ability to accurately discriminate between those who did and those who did not develop breast cancer. For example, random-effects meta-analyses of the performance of the
Connecting to Get Things Done: A Conceptual Model of the Process Used to Respond to Bias Incidents
LePeau, Lucy A.; Morgan, Demetri L.; Zimmerman, Hilary B.; Snipes, Jeremy T.; Marcotte, Beth A.
2016-01-01
In this study, we interviewed victims of bias incidents and members of a bias response team to investigate the process the team used to respond to incidents. Incidents included acts of sexism, homophobia, and racism on a large, predominantly White research university in the Midwest. Data were analyzed using a 4-stage coding process. The emergent…
Directory of Open Access Journals (Sweden)
Esther D. Kim
2017-11-01
Discussion: Higher AIx and cPP, which are indicative of abnormal wave reflections in distal vessels, are associated with, and might contribute to, declining cognitive function in patients starting hemodialysis.
Dynamics of synthetic drugs transmission model with psychological addicts and general incidence rate
Ma, Mingju; Liu, Sanyang; Xiang, Hong; Li, Jun
2018-02-01
Synthetic drugs are replacing traditional ones and becoming the main popular ones gradually, which have given rise to serious social issues in recent years. In this paper, a synthetic drugs transmission model with psychological addicts and general contact rate is proposed. The local and global stabilities are decided by the basic reproduction number R0. By analyzing the sensitivity of parameters, we obtain that controlling psychological addiction is better than drugs treatment. These results are verified by numerical simulations.
2009-09-01
Robert F. Dell Chairman, Department of Operations Research iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT We develop a modeling tool to...Tauro AUSTRIA Trieste JAPAN Tokyo BANGLADESH Chittagong MALAYSIA Singapore BELGIUM Antwerp NETHERLANDS Rotterdam BRAZIL Santos NEW ZEALAND Tauranga... MALAYSIA Albany, NY 37 NETHERLANDS Albany, NY 47 SOUTH KOREA Albany, NY 65 THAILAND Albany, NY 55 UNITED KINGDOM Albany, NY 41 Origin Destination 2007
Exact 2-point function in Hermitian matrix model
International Nuclear Information System (INIS)
Morozov, A.; Shakirov, Sh.
2009-01-01
J. Harer and D. Zagier have found a strikingly simple generating function [1,2] for exact (all-genera) 1-point correlators in the Gaussian Hermitian matrix model. In this paper we generalize their result to 2-point correlators, using Toda integrability of the model. Remarkably, this exact 2-point correlation function turns out to be an elementary function - arctangent. Relation to the standard 2-point resolvents is pointed out. Some attempts of generalization to 3-point and higher functions are described.
Energy Technology Data Exchange (ETDEWEB)
Donovan, E. M.; James, H.; Bonora, M.; Yarnold, J. R.; Evans, P. M. [Joint Department of Physics, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton SM2 5PT (United Kingdom); Physics Department, Ipswich Hospital NHS Foundation Trust, Ipswich IP4 5PD (United Kingdom); Department of Academic Radiotherapy, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton SM2 5PT, United Kingdom and School of Radiotherapy, University of Milan, Milan 20122 (Italy); Department of Academic Radiotherapy, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton SM2 5PT (United Kingdom); Centre for Vision Speech and Signal Processing, University of Surrey, Guildford GU2 7XH (United Kingdom)
2012-10-15
Purpose: To compare organ specific cancer incidence risks for standard and complex external beam radiotherapy (including cone beam CT verification) following breast conservation surgery for early breast cancer.Method: Doses from breast radiotherapy and kilovoltage cone beam CT (CBCT) exposures were obtained from thermoluminescent dosimeter measurements in an anthropomorphic phantom in which the positions of radiosensitive organs were delineated. Five treatment deliveries were investigated: (i) conventional tangential field whole breast radiotherapy (WBRT), (ii) noncoplanar conformal delivery applicable to accelerated partial beast irradiation (APBI), (iii) two-volume simultaneous integrated boost (SIB) treatment, (iv) forward planned three-volume SIB, and (v) inverse-planned three volume SIB. Conformal and intensity modulated radiotherapy methods were used to plan the complex treatments. Techniques spanned the range from simple methods appropriate for patient cohorts with a low cancer recurrence risk to complex plans relevant to cohorts with high recurrence risk. Delineated organs at risk included brain, salivary glands, thyroid, contralateral breast, left and right lung, esophagus, stomach, liver, colon, and bladder. Biological Effects of Ionizing Radiation (BEIR) VII cancer incidence models were applied to the measured mean organ doses to determine lifetime attributable risk (LAR) for ages at exposure from 35 to 80 yr according to radiotherapy techniques, and included dose from the CBCT imaging. Results: All LAR decreased with age at exposure and were lowest for brain, thyroid, liver, and bladder (<0.1%). There was little dependence of LAR on radiotherapy technique for these organs and for colon and stomach. LAR values for the lungs for the three SIB techniques were two to three times those from WBRT and APBI. Uncertainties in the LAR models outweigh any differences in lung LAR between the SIB methods. Constraints in the planning of the SIB methods ensured that
Multiple time scales in modeling the incidence of infections acquired in intensive care units
Directory of Open Access Journals (Sweden)
Martin Wolkewitz
2016-09-01
Full Text Available Abstract Background When patients are admitted to an intensive care unit (ICU their risk of getting an infection will be highly depend on the length of stay at-risk in the ICU. In addition, risk of infection is likely to vary over calendar time as a result of fluctuations in the prevalence of the pathogen on the ward. Hence risk of infection is expected to depend on two time scales (time in ICU and calendar time as well as competing events (discharge or death and their spatial location. The purpose of this paper is to develop and apply appropriate statistical models for the risk of ICU-acquired infection accounting for multiple time scales, competing risks and the spatial clustering of the data. Methods A multi-center data base from a Spanish surveillance network was used to study the occurrence of an infection due to Methicillin-resistant Staphylococcus aureus (MRSA. The analysis included 84,843 patient admissions between January 2006 and December 2011 from 81 ICUs. Stratified Cox models were used to study multiple time scales while accounting for spatial clustering of the data (patients within ICUs and for death or discharge as competing events for MRSA infection. Results Both time scales, time in ICU and calendar time, are highly associated with the MRSA hazard rate and cumulative risk. When using only one basic time scale, the interpretation and magnitude of several patient-individual risk factors differed. Risk factors concerning the severity of illness were more pronounced when using only calendar time. These differences disappeared when using both time scales simultaneously. Conclusions The time-dependent dynamics of infections is complex and should be studied with models allowing for multiple time scales. For patient individual risk-factors we recommend stratified Cox regression models for competing events with ICU time as the basic time scale and calendar time as a covariate. The inclusion of calendar time and stratification by ICU
On Support Functions for the Development of MFM Models
DEFF Research Database (Denmark)
Heussen, Kai; Lind, Morten
2012-01-01
a review of MFM applications, and contextualizes the model development with respect to process design and operation knowledge. Developing a perspective for an environment for MFM-oriented model- and application-development a tool-chain is outlined and relevant software functions are discussed......A modeling environment and methodology are necessary to ensure quality and reusability of models in any domain. For MFM in particular, as a tool for modeling complex systems, awareness has been increasing for this need. Introducing the context of modeling support functions, this paper provides....... With a perspective on MFM-modeling for existing processes and automation design, modeling stages and corresponding formal model properties are identified. Finally, practically feasible support functions and model-checks to support the model-development are suggested....
Rezaei, Sajjad; Asgari, Karim; Yousefzadeh, Shahrokh; Moosavi, Heshmat-Allah; Kazemnejad, Ehsan
2012-01-01
Neurosurgical treatment and the severity of head injury (HI) can have remarkable effect on patients' neuropsychiatric outcomes. This research aimed to study the effect of these factors on cognitive functioning, general health and incidence of mental disorders in patients with a traumatic brain injury (TBI). In this descriptive, longitudinal study, 206 TBI patients entered the study by consecutive sampling; they were then compared according to neurosurgery status and severity of their HI. Both groups underwent neurosurgical and psychological examinations. The mini mental state examination (MMSE) and general health questionnaire-28 items (GHQ-28) were administered to the study participants. At follow-up, four months later, the groups underwent a structured clinical interview by a psychiatrist based on the diagnostic and statistical manual of mental disorders, fourth edition (DSM-IV) diagnostic criteria regarding the presence of mental disorders. Analysis of covariance (ANCOVA) and multivariate analysis of covariance (MANCOVA) were performed and adjusted for the effect of confounding variables (age, gender, Glasgow outcome scale (GOS) , and level of education). The severity of HI had the most significant effect for the following variables; cognitive functioning and physical symptoms (P < 0.05). The effect of the neurosurgical treatment factor was not significant; however, the interaction effect of the two variables on social dysfunction, and total score of the GHQ-28 questionnaire appeared to be significant (P < 0.05). Fisher's exact test indicated that after a four month follow-up period, no significant differences were seen between the two groups (with or without neurosurgery) in the incidence of mental disorders, while χ(2) Test showed that having a more severe HI is significantly correlated with the incidence of mental disorders (P < 0.01). The implications of this study should be discussed with an emphasis on negative, effective factors on the cognitive
Yu, Wenya; Lv, Yipeng; Hu, Chaoqun; Liu, Xu; Chen, Haiping; Xue, Chen; Zhang, Lulu
2018-01-01
Emergency medical system for mass casualty incidents (EMS-MCIs) is a global issue. However, China lacks such studies extremely, which cannot meet the requirement of rapid decision-support system. This study aims to realize modeling EMS-MCIs in Shanghai, to improve mass casualty incident (MCI) rescue efficiency in China, and to provide a possible method of making rapid rescue decisions during MCIs. This study established a system dynamics (SD) model of EMS-MCIs using the Vensim DSS program. Intervention scenarios were designed as adjusting scales of MCIs, allocation of ambulances, allocation of emergency medical staff, and efficiency of organization and command. Mortality increased with the increasing scale of MCIs, medical rescue capability of hospitals was relatively good, but the efficiency of organization and command was poor, and the prehospital time was too long. Mortality declined significantly when increasing ambulances and improving the efficiency of organization and command; triage and on-site first-aid time were shortened if increasing the availability of emergency medical staff. The effect was the most evident when 2,000 people were involved in MCIs; however, the influence was very small under the scale of 5,000 people. The keys to decrease the mortality of MCIs were shortening the prehospital time and improving the efficiency of organization and command. For small-scale MCIs, improving the utilization rate of health resources was important in decreasing the mortality. For large-scale MCIs, increasing the number of ambulances and emergency medical professionals was the core to decrease prehospital time and mortality. For super-large-scale MCIs, increasing health resources was the premise.
Elul, Batya; Wools-Kaloustian, Kara K; Wu, Yingfeng; Musick, Beverly S; Nuwagaba-Biribonwoha, Harriet; Nash, Denis; Ayaya, Samuel; Bukusi, Elizabeth; Okong, Pius; Otieno, Juliana; Wabwire, Deo; Kambugu, Andrew; Yiannoutsos, Constantin T
2016-07-01
Scale-up of triple-drug antiretroviral therapy (ART) in Africa has transformed the context of childbearing for HIV-positive women and may impact pregnancy incidence in HIV programs. Using observational data from 47,313 HIV-positive women enrolled at 26 HIV clinics in Kenya and Uganda between 2001 and 2009, we calculated the crude cumulative incidence of pregnancy for the pre-ART and on-ART periods. The causal effect of ART use on incident pregnancy was assessed using inverse probability weighted marginal structural models, and the relationship was further explored in multivariable Cox models. Crude cumulative pregnancy incidence at 1 year after enrollment/ART initiation was 4.0% and 3.9% during the pre-ART and on-ART periods, respectively. In marginal structural models, ART use was not significantly associated with incident pregnancy [hazard ratio = 1.06; 95% confidence interval (CI): 0.99 to 1.12]. Similarly, in Cox models, there was no significant relationship between ART use and incident pregnancy (cause-specific hazard ratio: 0.98; 95% CI: 0.91 to 1.05), but effect modification was observed. Specifically, women who were pregnant at enrollment and on ART had an increased risk of incident pregnancy compared to those not pregnant at enrollment and not on ART (cause-specific hazard ratio: 1.11; 95% CI: 1.01 to 1.23). In this large cohort, ART initiation was not associated with incident pregnancy in the general population of women enrolling in HIV care but rather only among those pregnant at enrollment. This finding further highlights the importance of scaling up access to lifelong treatment for pregnant women.
Modelling Strategies for Functional Magnetic Resonance Imaging
DEFF Research Database (Denmark)
Madsen, Kristoffer Hougaard
2009-01-01
and generalisations to higher order arrays are considered. Additionally, an application of the natural conjugate prior for supervised learning in the general linear model to efficiently incorporate prior information for supervised analysis is presented. Further extensions include methods to model nuisance effects...... in fMIR data thereby suppressing noise for both supervised and unsupervised analysis techniques....
Functional Decomposition of Modeling and Simulation Terrain Database Generation Process
National Research Council Canada - National Science Library
Yakich, Valerie R; Lashlee, J. D
2008-01-01
.... This report documents the conceptual procedure as implemented by Lockheed Martin Simulation, Training, and Support and decomposes terrain database construction using the Integration Definition for Function Modeling (IDEF...
Directory of Open Access Journals (Sweden)
Daniel J Carter, MSc
2018-05-01
Full Text Available Summary: Background: The End TB Strategy and the Sustainable Development Goals (SDGs are intimately linked by their common targets and approaches. SDG 1 aims to end extreme poverty and expand social protection coverage by 2030. Achievement of SDG 1 is likely to affect the tuberculosis epidemic through a range of pathways. We estimate the reduction in global tuberculosis incidence that could be obtained by reaching SDG 1. Methods: We developed a conceptual framework linking key indicators of SDG 1 progress to tuberculosis incidence via well described risk factor pathways and populated it with data from the SDG data repository and the WHO tuberculosis database for 192 countries. Correlations and mediation analyses informed the strength of the association between the SDG 1 subtargets and tuberculosis incidence, resulting in a simplified framework for modelling. The simplified framework linked key indicators for SDG 1 directly to tuberculosis incidence. We applied an exponential decay model based on linear associations between SDG 1 indicators and tuberculosis incidence to estimate tuberculosis incidence in 2035. Findings: Ending extreme poverty resulted in a reduction in global incidence of tuberculosis of 33·4% (95% credible interval 15·5–44·5 by 2035 and expanding social protection coverage resulted in a reduction in incidence of 76·1% (45·2–89·9 by 2035; both pathways together resulted in a reduction in incidence of 84·3% (54·7–94·9. Interpretation: Full achievement of SDG 1 could have a substantial effect on the global burden of tuberculosis. Cross-sectoral approaches that promote poverty reduction and social protection expansion will be crucial complements to health interventions, accelerating progress towards the End TB targets. Funding: World Health Organization.
Carter, Daniel J; Glaziou, Philippe; Lönnroth, Knut; Siroka, Andrew; Floyd, Katherine; Weil, Diana; Raviglione, Mario; Houben, Rein M G J; Boccia, Delia
2018-05-01
The End TB Strategy and the Sustainable Development Goals (SDGs) are intimately linked by their common targets and approaches. SDG 1 aims to end extreme poverty and expand social protection coverage by 2030. Achievement of SDG 1 is likely to affect the tuberculosis epidemic through a range of pathways. We estimate the reduction in global tuberculosis incidence that could be obtained by reaching SDG 1. We developed a conceptual framework linking key indicators of SDG 1 progress to tuberculosis incidence via well described risk factor pathways and populated it with data from the SDG data repository and the WHO tuberculosis database for 192 countries. Correlations and mediation analyses informed the strength of the association between the SDG 1 subtargets and tuberculosis incidence, resulting in a simplified framework for modelling. The simplified framework linked key indicators for SDG 1 directly to tuberculosis incidence. We applied an exponential decay model based on linear associations between SDG 1 indicators and tuberculosis incidence to estimate tuberculosis incidence in 2035. Ending extreme poverty resulted in a reduction in global incidence of tuberculosis of 33·4% (95% credible interval 15·5-44·5) by 2035 and expanding social protection coverage resulted in a reduction in incidence of 76·1% (45·2-89·9) by 2035; both pathways together resulted in a reduction in incidence of 84·3% (54·7-94·9). Full achievement of SDG 1 could have a substantial effect on the global burden of tuberculosis. Cross-sectoral approaches that promote poverty reduction and social protection expansion will be crucial complements to health interventions, accelerating progress towards the End TB targets. World Health Organization. Copyright © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.
Validation of a multi-marker model for the prediction of incident type 2 diabetes mellitus
DEFF Research Database (Denmark)
Lyssenko, Valeriya; Jørgensen, Torben; Gerwien, Robert W
2012-01-01
Purpose: To assess performance of a biomarker-based score that predicts the five-year risk of diabetes (Diabetes Risk Score, DRS) in an independent cohort that included 15-year follow-up. Method: DRS was developed on the Inter99 cohort, and validated on the Botnia cohort. Performance...... was benchmarked against other risk-assessment tools comparing calibration, time to event analysis, and net reclassification. Results: The area under the receiver-operating characteristic curve (AUC) was 0.84 for the Inter99 cohort and 0.78 for the Botnia cohort. In the Botnia cohort, DRS provided better...... discrimination than fasting plasma glucose (FPG), homeostasis model assessment of insulin resistance, oral glucose tolerance test or risk scores derived from Framingham or San Antonio Study cohorts. Overall reclassification with DRS was significantly better than using FPG and glucose tolerance status (p
International Nuclear Information System (INIS)
Donovan, E. M.; James, H.; Bonora, M.; Yarnold, J. R.; Evans, P. M.
2012-01-01
Purpose: To compare organ specific cancer incidence risks for standard and complex external beam radiotherapy (including cone beam CT verification) following breast conservation surgery for early breast cancer.Method: Doses from breast radiotherapy and kilovoltage cone beam CT (CBCT) exposures were obtained from thermoluminescent dosimeter measurements in an anthropomorphic phantom in which the positions of radiosensitive organs were delineated. Five treatment deliveries were investigated: (i) conventional tangential field whole breast radiotherapy (WBRT), (ii) noncoplanar conformal delivery applicable to accelerated partial beast irradiation (APBI), (iii) two-volume simultaneous integrated boost (SIB) treatment, (iv) forward planned three-volume SIB, and (v) inverse-planned three volume SIB. Conformal and intensity modulated radiotherapy methods were used to plan the complex treatments. Techniques spanned the range from simple methods appropriate for patient cohorts with a low cancer recurrence risk to complex plans relevant to cohorts with high recurrence risk. Delineated organs at risk included brain, salivary glands, thyroid, contralateral breast, left and right lung, esophagus, stomach, liver, colon, and bladder. Biological Effects of Ionizing Radiation (BEIR) VII cancer incidence models were applied to the measured mean organ doses to determine lifetime attributable risk (LAR) for ages at exposure from 35 to 80 yr according to radiotherapy techniques, and included dose from the CBCT imaging. Results: All LAR decreased with age at exposure and were lowest for brain, thyroid, liver, and bladder (<0.1%). There was little dependence of LAR on radiotherapy technique for these organs and for colon and stomach. LAR values for the lungs for the three SIB techniques were two to three times those from WBRT and APBI. Uncertainties in the LAR models outweigh any differences in lung LAR between the SIB methods. Constraints in the planning of the SIB methods ensured that
Mechanical modeling of skeletal muscle functioning
van der Linden, B.J.J.J.
1998-01-01
For movement of body or body segments is combined effort needed of the central nervous system and the muscular-skeletal system. This thesis deals with the mechanical functioning of skeletal muscle. That muscles come in a large variety of geometries, suggest the existence of a relation between muscle
Partially linear varying coefficient models stratified by a functional covariate
Maity, Arnab; Huang, Jianhua Z.
2012-01-01
We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric
Pizzitutti, Francesco; Pan, William; Barbieri, Alisson; Miranda, J Jaime; Feingold, Beth; Guedes, Gilvan R; Alarcon-Valenzuela, Javiera; Mena, Carlos F
2015-12-22
The Amazon environment has been exposed in the last decades to radical changes that have been accompanied by a remarkable rise of both Plasmodium falciparum and Plasmodium vivax malaria. The malaria transmission process is highly influenced by factors such as spatial and temporal heterogeneities of the environment and individual-based characteristics of mosquitoes and humans populations. All these determinant factors can be simulated effectively trough agent-based models. This paper presents a validated agent-based model of local-scale malaria transmission. The model reproduces the environment of a typical riverine village in the northern Peruvian Amazon, where the malaria transmission is highly seasonal and apparently associated with flooding of large areas caused by the neighbouring river. Agents representing humans, mosquitoes and the two species of Plasmodium (P. falciparum and P. vivax) are simulated in a spatially explicit representation of the environment around the village. The model environment includes: climate, people houses positions and elevation. A representation of changes in the mosquito breeding areas extension caused by the river flooding is also included in the simulation environment. A calibration process was carried out to reproduce the variations of the malaria monthly incidence over a period of 3 years. The calibrated model is also able to reproduce the spatial heterogeneities of local scale malaria transmission. A "what if" eradication strategy scenario is proposed: if the mosquito breeding sites are eliminated through mosquito larva habitat management in a buffer area extended at least 200 m around the village, the malaria transmission is eradicated from the village. The use of agent-based models can reproduce effectively the spatiotemporal variations of the malaria transmission in a low endemicity environment dominated by river floodings like in the Amazon.
Model predictive control using fuzzy decision functions
Kaymak, U.; Costa Sousa, da J.M.
2001-01-01
Fuzzy predictive control integrates conventional model predictive control with techniques from fuzzy multicriteria decision making, translating the goals and the constraints to predictive control in a transparent way. The information regarding the (fuzzy) goals and the (fuzzy) constraints of the
SOFTWARE DESIGN MODELLING WITH FUNCTIONAL PETRI NETS
African Journals Online (AJOL)
Dr Obe
the system, which can be described as a set of conditions. ... FPN Software prototype proposed for the conventional programming construct: if-then-else ... mathematical modeling tool allowing for ... methods and techniques of software design.
Building functional networks of spiking model neurons.
Abbott, L F; DePasquale, Brian; Memmesheimer, Raoul-Martin
2016-03-01
Most of the networks used by computer scientists and many of those studied by modelers in neuroscience represent unit activities as continuous variables. Neurons, however, communicate primarily through discontinuous spiking. We review methods for transferring our ability to construct interesting networks that perform relevant tasks from the artificial continuous domain to more realistic spiking network models. These methods raise a number of issues that warrant further theoretical and experimental study.
The characteristic function of rough Heston models
Euch, Omar El; Rosenbaum, Mathieu
2016-01-01
It has been recently shown that rough volatility models, where the volatility is driven by a fractional Brownian motion with small Hurst parameter, provide very relevant dynamics in order to reproduce the behavior of both historical and implied volatilities. However, due to the non-Markovian nature of the fractional Brownian motion, they raise new issues when it comes to derivatives pricing. Using an original link between nearly unstable Hawkes processes and fractional volatility models, we c...
Directory of Open Access Journals (Sweden)
Jisheng Zhang
2015-06-01
Full Text Available It is essential for transportation management centers to equip and manage a network of fixed and mobile sensors in order to quickly detect traffic incidents and further monitor the related impact areas, especially for high-impact accidents with dramatic traffic congestion propagation. As emerging small Unmanned Aerial Vehicles (UAVs start to have a more flexible regulation environment, it is critically important to fully explore the potential for of using UAVs for monitoring recurring and non-recurring traffic conditions and special events on transportation networks. This paper presents a space-time network- based modeling framework for integrated fixed and mobile sensor networks, in order to provide a rapid and systematic road traffic monitoring mechanism. By constructing a discretized space-time network to characterize not only the speed for UAVs but also the time-sensitive impact areas of traffic congestion, we formulate the problem as a linear integer programming model to minimize the detection delay cost and operational cost, subject to feasible flying route constraints. A Lagrangian relaxation solution framework is developed to decompose the original complex problem into a series of computationally efficient time-dependent and least cost path finding sub-problems. Several examples are used to demonstrate the results of proposed models in UAVs’ route planning for small and medium-scale networks.
Directory of Open Access Journals (Sweden)
Lianfa Li
2018-02-01
Full Text Available Abstract Background As a common infectious disease, hand, foot and mouth disease (HFMD is affected by multiple environmental and socioeconomic factors, and its pathogenesis is complex. Furthermore, the transmission of HFMD is characterized by strong spatial clustering and autocorrelation, and the classical statistical approach may be biased without consideration of spatial autocorrelation. In this paper, we propose to embed spatial characteristics into a spatiotemporal additive model to improve HFMD incidence assessment. Methods Using incidence data (6439 samples from 137 monitoring district for Shandong Province, China, along with meteorological, environmental and socioeconomic spatial and spatiotemporal covariate data, we proposed a spatiotemporal mixed model to estimate HFMD incidence. Geo-additive regression was used to model the non-linear effects of the covariates on the incidence risk of HFMD in univariate and multivariate models. Furthermore, the spatial effect was constructed to capture spatial autocorrelation at the sub-regional scale, and clusters (hotspots of high risk were generated using spatiotemporal scanning statistics as a predictor. Linear and non-linear effects were compared to illustrate the usefulness of non-linear associations. Patterns of spatial effects and clusters were explored to illustrate the variation of the HFMD incidence across geographical sub-regions. To validate our approach, 10-fold cross-validation was conducted. Results The results showed that there were significant non-linear associations of the temporal index, spatiotemporal meteorological factors and spatial environmental and socioeconomic factors with HFMD incidence. Furthermore, there were strong spatial autocorrelation and clusters for the HFMD incidence. Spatiotemporal meteorological parameters, the normalized difference vegetation index (NDVI, the temporal index, spatiotemporal clustering and spatial effects played important roles as predictors in
Afifi, Tracie O; Taillieu, Tamara; Cheung, Kristene; Katz, Laurence Y; Tonmyr, Lil; Sareen, Jitender
2015-07-01
Identifying child and household characteristics that are associated with specific child maltreatment types and child functional impairment are important for informing prevention and intervention efforts. Our objectives were to examine the distribution of several child and household characteristics among substantiated child maltreatment types in Canada; to determine if a specific child maltreatment type relative to all other types was associated with increased odds of child functional impairment; and to determine which child and household characteristics were associated with child functional impairment. Data were from the Canadian Incidence Study of Reported Child Abuse and Neglect (collection 2008) from 112 child welfare sites across Canada (n = 6163 children). Physical abuse, sexual abuse, and emotional maltreatment were highly prevalent among children aged 10 to 15 years. For single types of child maltreatment, the highest prevalence of single-parent homes (50.6%), social assistance (43.0%), running out of money regularly (30.7%), and unsafe housing (30.9%) were reported for substantiated cases of neglect. Being male, older age, living in a single-parent home, household running out of money, moving 2 or more times in the past year, and household overcrowding were associated with increased odds of child functional impairment. More work is warranted to determine if providing particular resources for single-parent families, financial counselling, and facilitating adequate and stable housing for families with child maltreatment histories or at risk for child maltreatment could be effective for improving child functional outcomes.
Afifi, Tracie O; Taillieu, Tamara; Cheung, Kristene; Katz, Laurence Y; Tonmyr, Lil; Sareen, Jitender
2015-01-01
Objective: Identifying child and household characteristics that are associated with specific child maltreatment types and child functional impairment are important for informing prevention and intervention efforts. Our objectives were to examine the distribution of several child and household characteristics among substantiated child maltreatment types in Canada; to determine if a specific child maltreatment type relative to all other types was associated with increased odds of child functional impairment; and to determine which child and household characteristics were associated with child functional impairment. Method: Data were from the Canadian Incidence Study of Reported Child Abuse and Neglect (collection 2008) from 112 child welfare sites across Canada (n = 6163 children). Results: Physical abuse, sexual abuse, and emotional maltreatment were highly prevalent among children aged 10 to 15 years. For single types of child maltreatment, the highest prevalence of single-parent homes (50.6%), social assistance (43.0%), running out of money regularly (30.7%), and unsafe housing (30.9%) were reported for substantiated cases of neglect. Being male, older age, living in a single-parent home, household running out of money, moving 2 or more times in the past year, and household overcrowding were associated with increased odds of child functional impairment. Conclusions: More work is warranted to determine if providing particular resources for single-parent families, financial counselling, and facilitating adequate and stable housing for families with child maltreatment histories or at risk for child maltreatment could be effective for improving child functional outcomes. PMID:26175390
Lee, Hsuei-Chen; Chang, Ku-Chou; Tsauo, Jau-Yih; Hung, Jen-Wen; Huang, Yu-Ching; Lin, Sang-I
2013-04-01
To evaluate effects of a multifactorial fall prevention program on fall incidence and physical function in community-dwelling older adults. Multicenter randomized controlled trial. Three medical centers and adjacent community health centers. Community-dwelling older adults (N=616) who have fallen in the previous year or are at risk of falling. After baseline assessment, eligible subjects were randomly allocated into the intervention group (IG) or the control group (CG), stratified by the Physiological Profile Assessment (PPA) fall risk level. The IG received a 3-month multifactorial intervention program including 8 weeks of exercise training, health education, home hazards evaluation/modification, along with medication review and ophthalmology/other specialty consults. The CG received health education brochures, referrals, and recommendations without direct exercise intervention. Primary outcome was fall incidence within 1 year. Secondary outcomes were PPA battery (overall fall risk index, vision, muscular strength, reaction time, balance, and proprioception), Timed Up & Go (TUG) test, Taiwan version of the International Physical Activity Questionnaire, EuroQol-5D, Geriatric Depression Scale (GDS), and the Falls Efficacy Scale-International at 3 months after randomization. Participants were 76±7 years old and included low risk 25.6%, moderate risk 25.6%, and marked risk 48.7%. The cumulative 1-year fall incidence was 25.2% in the IG and 27.6% in the CG (hazard ratio=.90; 95% confidence interval, .66-1.23). The IG improved more favorably than the CG on overall PPA fall risk index, reaction time, postural sway with eyes open, TUG test, and GDS, especially for those with marked fall risk. The multifactorial fall prevention program with exercise intervention improved functional performance at 3 months for community-dwelling older adults with risk of falls, but did not reduce falls at 1-year follow-up. Fall incidence might have been decreased simultaneously in both
Shi, Changgui; Hu, Bo; Guo, Lei; Cao, Peng; Tian, Ye; Ma, Jun; Chen, Yuanyuan; Wu, Huiqiao; Hu, Jinquan; Deng, Lianfu; Zhang, Ying; Yuan, Wen
2016-05-01
Osteogenesis imperfecta (OI) is a genetic bone dysplasia characterized by brittle bones with increased fracture risk. Although current treatment options to improve bone strength in OI focus on antiresorptive bisphosphonates, controlled clinical trials suggest they have an equivocal effect on reducing fracture risk. Strontium ranelate (SrR) is a promising therapy with a dual mode of action that is capable of simultaneously maintaining bone formation and reducing bone resorption, and may be beneficial for the treatment of OI. In this study, SrR therapy was investigated to assess its effects on fracture frequency and bone mass and strength in an animal model of OI, the oim/oim mouse. Three-week-old oim/oim and wt/wt mice were treated with either SrR or vehicle (Veh) for 11 weeks. After treatment, the average number of fractures sustained by SrR-treated oim/oim mice was significantly reduced compared to Veh-treated oim/oim mice. Micro-computed tomographic (μCT) analyses of femurs showed that both trabecular and cortical bone mass were significantly improved with SrR treatment in both genotypes. SrR significantly inhibited bone resorption, whereas bone formation indices were maintained. Biomechanical testing revealed improved bone structural properties in both oim/oim and wild-type (wt/wt) mice under the treatment, whereas no significant effects on bone brittleness and material quality were observed. In conclusion, SrR was able to effectively reduce fractures in oim/oim mice by improving bone mass and strength and thus represents a potential therapy for the treatment of pediatric OI. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.
Resnick, Barbara; Gruber-Baldini, Ann L; Hicks, Gregory; Ostir, Glen; Klinedinst, N Jennifer; Orwig, Denise; Magaziner, Jay
2016-07-01
Measurement of physical function post hip fracture has been conceptualized using multiple different measures. This study tested a comprehensive measurement model of physical function. This was a descriptive secondary data analysis including 168 men and 171 women post hip fracture. Using structural equation modeling, a measurement model of physical function which included grip strength, activities of daily living, instrumental activities of daily living, and performance was tested for fit at 2 and 12 months post hip fracture, and among male and female participants. Validity of the measurement model of physical function was evaluated based on how well the model explained physical activity, exercise, and social activities post hip fracture. The measurement model of physical function fit the data. The amount of variance the model or individual factors of the model explained varied depending on the activity. Decisions about the ideal way in which to measure physical function should be based on outcomes considered and participants. The measurement model of physical function is a reliable and valid method to comprehensively measure physical function across the hip fracture recovery trajectory. © 2015 Association of Rehabilitation Nurses.
Applications of model theory to functional analysis
Iovino, Jose
2014-01-01
During the last two decades, methods that originated within mathematical logic have exhibited powerful applications to Banach space theory, particularly set theory and model theory. This volume constitutes the first self-contained introduction to techniques of model theory in Banach space theory. The area of research has grown rapidly since this monograph's first appearance, but much of this material is still not readily available elsewhere. For instance, this volume offers a unified presentation of Krivine's theorem and the Krivine-Maurey theorem on stable Banach spaces, with emphasis on the
Diet models with linear goal programming: impact of achievement functions.
Gerdessen, J C; de Vries, J H M
2015-11-01
Diet models based on goal programming (GP) are valuable tools in designing diets that comply with nutritional, palatability and cost constraints. Results derived from GP models are usually very sensitive to the type of achievement function that is chosen.This paper aims to provide a methodological insight into several achievement functions. It describes the extended GP (EGP) achievement function, which enables the decision maker to use either a MinSum achievement function (which minimizes the sum of the unwanted deviations) or a MinMax achievement function (which minimizes the largest unwanted deviation), or a compromise between both. An additional advantage of EGP models is that from one set of data and weights multiple solutions can be obtained. We use small numerical examples to illustrate the 'mechanics' of achievement functions. Then, the EGP achievement function is demonstrated on a diet problem with 144 foods, 19 nutrients and several types of palatability constraints, in which the nutritional constraints are modeled with fuzzy sets. Choice of achievement function affects the results of diet models. MinSum achievement functions can give rise to solutions that are sensitive to weight changes, and that pile all unwanted deviations on a limited number of nutritional constraints. MinMax achievement functions spread the unwanted deviations as evenly as possible, but may create many (small) deviations. EGP comprises both types of achievement functions, as well as compromises between them. It can thus, from one data set, find a range of solutions with various properties.
Refined functional relations for the elliptic SOS model
Energy Technology Data Exchange (ETDEWEB)
Galleas, W., E-mail: w.galleas@uu.nl [ARC Centre of Excellence for the Mathematics and Statistics of Complex Systems, University of Melbourne, VIC 3010 (Australia)
2013-02-21
In this work we refine the method presented in Galleas (2012) [1] and obtain a novel kind of functional equation determining the partition function of the elliptic SOS model with domain wall boundaries. This functional relation arises from the dynamical Yang-Baxter relation and its solution is given in terms of multiple contour integrals.
Refined functional relations for the elliptic SOS model
International Nuclear Information System (INIS)
Galleas, W.
2013-01-01
In this work we refine the method presented in Galleas (2012) [1] and obtain a novel kind of functional equation determining the partition function of the elliptic SOS model with domain wall boundaries. This functional relation arises from the dynamical Yang–Baxter relation and its solution is given in terms of multiple contour integrals.
Density functional theory and multiscale materials modeling
Indian Academy of Sciences (India)
One of the vital ingredients in the theoretical tools useful in materials modeling at all the length scales of interest is the concept of density. In the microscopic length scale, it is the electron density that has played a major role in providing a deeper understanding of chemical binding in atoms, molecules and solids.
Quark fragmentation function and the nonlinear chiral quark model
International Nuclear Information System (INIS)
Zhu, Z.K.
1993-01-01
The scaling law of the fragmentation function has been proved in this paper. With that, we show that low-P T quark fragmentation function can be studied as a low energy physocs in the light-cone coordinate frame. We therefore use the nonlinear chiral quark model which is able to study the low energy physics under scale Λ CSB to study such a function. Meanwhile the formalism for studying the quark fragmentation function has been established. The nonlinear chiral quark model is quantized on the light-front. We then use old-fashioned perturbation theory to study the quark fragmentation function. Our first order result for such a function shows in agreement with the phenomenological model study of e + e - jet. The probability for u,d pair formation in the e + e - jet from our calculation is also in agreement with the phenomenological model results
Fukuma, Shingo; Shimizu, Sayaka; Shintani, Ayumi; Kamitani, Tsukasa; Akizawa, Tadao; Fukuhara, Shunichi
2017-09-05
Among aging hemodialysis patients, loss of physical function has become a major issue. We developed and validated a model of predicting loss of physical function among elderly hemodialysis patients. We conducted a cohort study involving maintenance hemodialysis patients ≥65 years of age from the Dialysis Outcomes and Practice Pattern Study in Japan. The derivation cohort included 593 early phase (1996-2004) patients and the temporal validation cohort included 447 late-phase (2005-12) patients. The main outcome was the incidence of loss of physical function, defined as the 12-item Short Form Health Survey physical function score decreasing to 0 within a year. Using backward stepwise logistic regression by Akaike's Information Criteria, six predictors (age, gender, dementia, mental health, moderate activity and ascending stairs) were selected for the final model. Points were assigned based on the regression coefficients and the total score was calculated by summing the points for each predictor. In total, 65 (11.0%) and 53 (11.9%) hemodialysis patients lost their physical function within 1 year in the derivation and validation cohorts, respectively. This model has good predictive performance quantified by both discrimination and calibration. The proportion of the loss of physical function increased sequentially through low-, middle-, and high-score categories based on the model (2.5%, 11.7% and 22.3% in the validation cohort, respectively). The loss of physical function was strongly associated with 1-year mortality [adjusted odds ratio 2.48 (95% confidence interval 1.26-4.91)]. We developed and validated a risk prediction model with good predictive performance for loss of physical function in elderly hemodialysis patients. Our simple prediction model may help physicians and patients make more informed decisions for healthy longevity. © The Author 2017. Published by Oxford University Press on behalf of ERA-EDTA.
Directory of Open Access Journals (Sweden)
Masahiko Yazawa
Full Text Available Although dialysis is typically started in an effort to prolong survival, mortality is reportedly high in the first few months. However, it remains unclear whether this is true in Japanese patients who tend to have a better prognosis than other ethnicities, and if health conditions such as functional status (FS at initiation of dialysis influence prognosis.We investigated the epidemiology of early death and its association with FS using Japanese national registry data in 2007, which included 35,415 patients on incident dialysis and 7,664 with FS data. The main outcome was early death, defined as death within 3 months after initiation of hemodialysis (HD. The main predictor was FS at initiation of HD. Levels of functional disability were categorized as follows: severe (bedridden, moderate (overt difficulties in exerting basic activities of daily living, or mild/none (none or some functional disabilities.Early death remained relatively common, especially among elderly patients (overall: 7.1%; those aged ≥80 years: 15.8%. Severely and even only a moderately impaired FS were significantly associated with early death after starting dialysis (adjusted risk ratios: 3.93 and 2.38, respectively. The incidence of early death in those with impaired FS increased with age (36.5% in those with severely impaired FS and aged ≥80 years.Early death after starting dialysis was relatively common, especially among the elderly, even in Japanese patients. Further, early death was significantly associated with impaired FS at initiation of HD.
Directory of Open Access Journals (Sweden)
Annick Bórquez
2016-09-01
Full Text Available Programmatic planning in HIV requires estimates of the distribution of new HIV infections according to identifiable characteristics of individuals. In sub-Saharan Africa, robust routine data sources and historical epidemiological observations are available to inform and validate such estimates.We developed a predictive model, the Incidence Patterns Model (IPM, representing populations according to factors that have been demonstrated to be strongly associated with HIV acquisition risk: gender, marital/sexual activity status, geographic location, "key populations" based on risk behaviours (sex work, injecting drug use, and male-to-male sex, HIV and ART status within married or cohabiting unions, and circumcision status. The IPM estimates the distribution of new infections acquired by group based on these factors within a Bayesian framework accounting for regional prior information on demographic and epidemiological characteristics from trials or observational studies. We validated and trained the model against direct observations of HIV incidence by group in seven rounds of cohort data from four studies ("sites" conducted in Manicaland, Zimbabwe; Rakai, Uganda; Karonga, Malawi; and Kisesa, Tanzania. The IPM performed well, with the projections' credible intervals for the proportion of new infections per group overlapping the data's confidence intervals for all groups in all rounds of data. In terms of geographical distribution, the projections' credible intervals overlapped the confidence intervals for four out of seven rounds, which were used as proxies for administrative divisions in a country. We assessed model performance after internal training (within one site and external training (between sites by comparing mean posterior log-likelihoods and used the best model to estimate the distribution of HIV incidence in six countries (Gabon, Kenya, Malawi, Rwanda, Swaziland, and Zambia in the region. We subsequently inferred the potential
Bórquez, Annick; Cori, Anne; Pufall, Erica L; Kasule, Jingo; Slaymaker, Emma; Price, Alison; Elmes, Jocelyn; Zaba, Basia; Crampin, Amelia C; Kagaayi, Joseph; Lutalo, Tom; Urassa, Mark; Gregson, Simon; Hallett, Timothy B
2016-09-01
Programmatic planning in HIV requires estimates of the distribution of new HIV infections according to identifiable characteristics of individuals. In sub-Saharan Africa, robust routine data sources and historical epidemiological observations are available to inform and validate such estimates. We developed a predictive model, the Incidence Patterns Model (IPM), representing populations according to factors that have been demonstrated to be strongly associated with HIV acquisition risk: gender, marital/sexual activity status, geographic location, "key populations" based on risk behaviours (sex work, injecting drug use, and male-to-male sex), HIV and ART status within married or cohabiting unions, and circumcision status. The IPM estimates the distribution of new infections acquired by group based on these factors within a Bayesian framework accounting for regional prior information on demographic and epidemiological characteristics from trials or observational studies. We validated and trained the model against direct observations of HIV incidence by group in seven rounds of cohort data from four studies ("sites") conducted in Manicaland, Zimbabwe; Rakai, Uganda; Karonga, Malawi; and Kisesa, Tanzania. The IPM performed well, with the projections' credible intervals for the proportion of new infections per group overlapping the data's confidence intervals for all groups in all rounds of data. In terms of geographical distribution, the projections' credible intervals overlapped the confidence intervals for four out of seven rounds, which were used as proxies for administrative divisions in a country. We assessed model performance after internal training (within one site) and external training (between sites) by comparing mean posterior log-likelihoods and used the best model to estimate the distribution of HIV incidence in six countries (Gabon, Kenya, Malawi, Rwanda, Swaziland, and Zambia) in the region. We subsequently inferred the potential contribution of each
Local and Global Function Model of the Liver
Energy Technology Data Exchange (ETDEWEB)
Wang, Hesheng, E-mail: hesheng@umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Feng, Mary [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Jackson, Andrew [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Ten Haken, Randall K.; Lawrence, Theodore S. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Cao, Yue [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Department of Radiology, University of Michigan, Ann Arbor, Michigan (United States); Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan (United States)
2016-01-01
Purpose: To develop a local and global function model in the liver based on regional and organ function measurements to support individualized adaptive radiation therapy (RT). Methods and Materials: A local and global model for liver function was developed to include both functional volume and the effect of functional variation of subunits. Adopting the assumption of parallel architecture in the liver, the global function was composed of a sum of local function probabilities of subunits, varying between 0 and 1. The model was fit to 59 datasets of liver regional and organ function measures from 23 patients obtained before, during, and 1 month after RT. The local function probabilities of subunits were modeled by a sigmoid function in relating to MRI-derived portal venous perfusion values. The global function was fitted to a logarithm of an indocyanine green retention rate at 15 minutes (an overall liver function measure). Cross-validation was performed by leave-m-out tests. The model was further evaluated by fitting to the data divided according to whether the patients had hepatocellular carcinoma (HCC) or not. Results: The liver function model showed that (1) a perfusion value of 68.6 mL/(100 g · min) yielded a local function probability of 0.5; (2) the probability reached 0.9 at a perfusion value of 98 mL/(100 g · min); and (3) at a probability of 0.03 [corresponding perfusion of 38 mL/(100 g · min)] or lower, the contribution to global function was lost. Cross-validations showed that the model parameters were stable. The model fitted to the data from the patients with HCC indicated that the same amount of portal venous perfusion was translated into less local function probability than in the patients with non-HCC tumors. Conclusions: The developed liver function model could provide a means to better assess individual and regional dose-responses of hepatic functions, and provide guidance for individualized treatment planning of RT.
Modelling of functional systems of managerial accounting
Directory of Open Access Journals (Sweden)
O.V. Fomina
2017-12-01
Full Text Available The modern stage of managerial accounting development takes place under the powerful influence of managerial innovations. The article aimed at the development of integrational model of budgeting and the system of balanced indices in the system of managerial accounting that will contribute the increasing of relevance for making managerial decisions by managers of different levels management. As a result of the study the author proposed the highly pragmatical integration model of budgeting and system of the balanced indices in the system of managerial accounting, which is realized by the development of the system of gathering, consolidation, analysis, and interpretation of financial and nonfinancial information, contributes the increasing of relevance for making managerial decisions on the base of coordination and effective and purpose orientation both strategical and operative resources of an enterprise. The effective integrational process of the system components makes it possible to distribute limited resources rationally taking into account prospective purposes and strategic initiatives, to carry
Directory of Open Access Journals (Sweden)
Marcia Regina Gianotti Franco
Full Text Available Abstract Introduction: Data on impact of high body mass index (BMI on mortality of patients on peritoneal dialysis (PD, especially among elderly, are inconsistent. Objective: To evaluate impact of BMI on cohort of incident elderly PD patients over time. Methods: Prospective multicenter cohort study (December / 2004-October/2007 with 674 patients. Socio-demographic and clinical data evaluated with patients followed until death, transfer to hemodialysis (HD, recovery of renal function, loss of follow-up or transplant. Patients were divided into incident on renal replacement therapy (RRT for PD (PD first: 230 and transferred from hemodialysis (HD first: 444. Analysis was performed comparing these two groups using chi-square or Kruskal Wallis. Similar analysis was used to compare patients on automated peritoneal dialysis (APD vs. continuous ambulatory peritoneal dialysis (CAPD. Data were compared between patients according to BMI by ANOVA, Kruskal Wallis or chi-square. For analysis of survival, Kaplan Meier method was used and to adjust confounding variables, Cox regression proportional hazard. Joint model for longitudinal and time-dependent data was conducted, assessing impact that a longitudinal variable displays on time of survival. Results: Malnourished patients (76.79 ± 7.53 years were older (p < 0.0001 with higher percentage of death (44.6%, p = 0.001; diabetes mellitus showed high prevalence in obese patients (68%, p < 0.0001; higher blood pressure levels (p = 0.002 were present in obese and overweight patients. Conclusions: Increased BMI variation over time proved to be a protective factor, with a decrease of about 1% in risk of death for every BMI unit earned.
Functional summary statistics for the Johnson-Mehl model
DEFF Research Database (Denmark)
Møller, Jesper; Ghorbani, Mohammad
The Johnson-Mehl germination-growth model is a spatio-temporal point process model which among other things have been used for the description of neurotransmitters datasets. However, for such datasets parametric Johnson-Mehl models fitted by maximum likelihood have yet not been evaluated by means...... of functional summary statistics. This paper therefore invents four functional summary statistics adapted to the Johnson-Mehl model, with two of them based on the second-order properties and the other two on the nuclei-boundary distances for the associated Johnson-Mehl tessellation. The functional summary...... statistics theoretical properties are investigated, non-parametric estimators are suggested, and their usefulness for model checking is examined in a simulation study. The functional summary statistics are also used for checking fitted parametric Johnson-Mehl models for a neurotransmitters dataset....
Modelling of multidimensional quantum systems by the numerical functional integration
International Nuclear Information System (INIS)
Lobanov, Yu.Yu.; Zhidkov, E.P.
1990-01-01
The employment of the numerical functional integration for the description of multidimensional systems in quantum and statistical physics is considered. For the multiple functional integrals with respect to Gaussian measures in the full separable metric spaces the new approximation formulas exact on a class of polynomial functionals of a given summary degree are constructed. The use of the formulas is demonstrated on example of computation of the Green function and the ground state energy in multidimensional Calogero model. 15 refs.; 2 tabs
Plachta, Kamil
2016-04-01
The paper presents a new algorithm that uses a combination of two models of BRDF functions: Torrance-Sparrow model and HTSG model. The knowledge of technical parameters of a surface is especially useful in the construction of the solar concentrator. The concentrator directs the reflected solar radiation on the surface of photovoltaic panels, increasing the amount of incident radiance. The software applying algorithm allows to calculate surface parameters of the solar concentrator. Performed simulation showing the share of diffuse component and directional component in reflected stream for surfaces made from particular materials. The impact of share of each component in reflected stream on the efficiency of the solar concentrator and photovoltaic surface has also been described. Subsequently, simulation change the value of voltage, current and power output of monocrystalline photovoltaic panels installed in a solar concentrator system has been made for selected surface of materials solar concentrator.
Functional Modelling for Fault Diagnosis and its application for NPP
DEFF Research Database (Denmark)
Lind, Morten; Zhang, Xinxin
2014-01-01
The paper presents functional modelling and its application for diagnosis in nuclear power plants.Functional modelling is defined and it is relevance for coping with the complexity of diagnosis in large scale systems like nuclear plants is explained. The diagnosis task is analyzed and it is demon...... operating modes. The FBR example illustrates how the modeling development effort can be managed by proper strategies including decomposition and reuse....
Smalley, Hannah K; Keskinocak, Pinar; Swann, Julie; Hinman, Alan
2015-11-17
In addition to improved sanitation, hygiene, and better access to safe water, oral cholera vaccines can help to control the spread of cholera in the short term. However, there is currently no systematic method for determining the best allocation of oral cholera vaccines to minimize disease incidence in a population where the disease is endemic and resources are limited. We present a mathematical model for optimally allocating vaccines in a region under varying levels of demographic and incidence data availability. The model addresses the questions of where, when, and how many doses of vaccines to send. Considering vaccine efficacies (which may vary based on age and the number of years since vaccination), we analyze distribution strategies which allocate vaccines over multiple years. Results indicate that, given appropriate surveillance data, targeting age groups and regions with the highest disease incidence should be the first priority, followed by other groups primarily in order of disease incidence, as this approach is the most life-saving and cost-effective. A lack of detailed incidence data results in distribution strategies which are not cost-effective and can lead to thousands more deaths from the disease. The mathematical model allows for what-if analysis for various vaccine distribution strategies by providing the ability to easily vary parameters such as numbers and sizes of regions and age groups, risk levels, vaccine price, vaccine efficacy, production capacity and budget. Copyright © 2015 Elsevier Ltd. All rights reserved.
Dapor, Maurizio
2005-01-01
Carbon films are deposited on various substrates (polymers, polyester fabrics, polyester yarns, metal alloys) both for experimental and technological motivations (medical devices, biocompatible coatings, food package and so on). Computational studies of the penetration of electron beams in supported thin film of carbon are very useful in order to compare the simulated results with analytical techniques data (obtained by scanning electron microscopy and/or Auger electron spectroscopy) and investigate the film characteristics. In the present paper, the few keV electron depth distribution and backscattering coefficient for the special case of film of carbon deposited on aluminium are investigated, by a Monte Carlo simulation, as a function of the incidence angle and primary electron energy. The simulated results can be used as a way to evaluate the carbon film thickness by a set of measurements of the backscattering coefficient.
Modeling dynamic functional connectivity using a wishart mixture model
DEFF Research Database (Denmark)
Nielsen, Søren Føns Vind; Madsen, Kristoffer Hougaard; Schmidt, Mikkel Nørgaard
2017-01-01
framework provides model selection by quantifying models generalization to new data. We use this to quantify the number of states within a prespecified window length. We further propose a heuristic procedure for choosing the window length based on contrasting for each window length the predictive...... together whereas short windows are more unstable and influenced by noise and we find that our heuristic correctly identifies an adequate level of complexity. On single subject resting state fMRI data we find that dynamic models generally outperform static models and using the proposed heuristic points...
Kaon fragmentation function from NJL-jet model
International Nuclear Information System (INIS)
Matevosyan, Hrayr H.; Thomas, Anthony W.; Bentz, Wolfgang
2010-01-01
The NJL-jet model provides a sound framework for calculating the fragmentation functions in an effective chiral quark theory, where the momentum and isospin sum rules are satisfied without the introduction of ad hoc parameters [1]. Earlier studies of the pion fragmentation functions using the Nambu-Jona-Lasinio (NJL) model within this framework showed good qualitative agreement with the empirical parameterizations. Here we extend the NJL-jet model by including the strange quark. The corrections to the pion fragmentation function and corresponding kaon fragmentation functions are calculated using the elementary quark to quark-meson fragmentation functions from NJL. The results for the kaon fragmentation function exhibit a qualitative agreement with the empirical parameterizations, while the unfavored strange quark fragmentation to pions is shown to be of the same order of magnitude as the unfavored light quark's. The results of these studies are expected to provide important guidance for the analysis of a large variety of semi-inclusive data.
Functional Characterization of a Porcine Emphysema Model
DEFF Research Database (Denmark)
Bruun, Camilla Sichlau; Jensen, Louise Kruse; Leifsson, Páll Skuli
2013-01-01
Lung emphysema is a central feature of chronic obstructive pulmonary disease (COPD), a frequent human disease worldwide. Cigarette smoking is the major cause of COPD, but genetic predisposition seems to be an important factor. Mutations in surfactant protein genes have been linked to COPD...... phenotypes in humans. Also, the catalytic activities of metalloproteinases (MMPs) are central in the pathogenesis of emphysema/COPD. Especially MMP9, but also MMP2, MMP7, and MMP12 seem to be involved in human emphysema. MMP12−/− mice are protected from smoke-induced emphysema. ITGB6−/− mice spontaneously...... develop age-related lung emphysema due to lack of ITGB6-TGF-β1 regulation of the MMP12 expression.A mutated pig phenotype characterized by age-related lung emphysema and resembling the ITGB6−/− mouse has been described previously. To investigate the emphysema pathogenesis in this pig model, we examined...
Predictive assessment of models for dynamic functional connectivity
DEFF Research Database (Denmark)
Nielsen, Søren Føns Vind; Schmidt, Mikkel Nørgaard; Madsen, Kristoffer Hougaard
2018-01-01
represent functional brain networks as a meta-stable process with a discrete number of states; however, there is a lack of consensus on how to perform model selection and learn the number of states, as well as a lack of understanding of how different modeling assumptions influence the estimated state......In neuroimaging, it has become evident that models of dynamic functional connectivity (dFC), which characterize how intrinsic brain organization changes over time, can provide a more detailed representation of brain function than traditional static analyses. Many dFC models in the literature...... dynamics. To address these issues, we consider a predictive likelihood approach to model assessment, where models are evaluated based on their predictive performance on held-out test data. Examining several prominent models of dFC (in their probabilistic formulations) we demonstrate our framework...
International Nuclear Information System (INIS)
Deo, Ravinesh C.; Wen, Xiaohu; Qi, Feng
2016-01-01
Highlights: • A forecasting model for short- and long-term global incident solar radiation (R_n) has been developed. • The support vector machine and discrete wavelet transformation algorithm has been integrated. • The precision of the wavelet-coupled hybrid model is assessed using several prediction score metrics. • The proposed model is an appealing tool for forecasting R_n in the present study region. - Abstract: A solar radiation forecasting model can be utilized is a scientific contrivance for investigating future viability of solar energy potentials. In this paper, a wavelet-coupled support vector machine (W-SVM) model was adopted to forecast global incident solar radiation based on the sunshine hours (S_t), minimum temperature (T_m_a_x), maximum temperature (T_m_a_x), windspeed (U), evaporation (E) and precipitation (P) as the predictor variables. To ascertain conclusive results, the merit of the W-SVM was benchmarked with the classical SVM model. For daily forecasting, sixteen months of data (01-March-2014 to 30-June-2015) partitioned into the train (65%) and test (35%) set for the three metropolitan stations (Brisbane City, Cairns Aero and Townsville Aero) were utilized. Data were decomposed into their wavelet sub-series by discrete wavelet transformation algorithm and summed up to create new series with one approximation and four levels of detail using Daubechies-2 mother wavelet. For daily forecasting, six model scenarios were formulated where the number of input was increased and the forecast was assessed by statistical metrics (correlation coefficient r; Willmott’s index d; Nash-Sutcliffe coefficient E_N_S; peak deviation P_d_v), distribution statistics and prediction errors (mean absolute error MAE; root mean square error RMSE; mean absolute percentage error MAPE; relative root mean square error RMSE). Results for daily forecasts showed that the W-SVM model outperformed the classical SVM model for optimum input combinations. A sensitivity
Directory of Open Access Journals (Sweden)
Mansour Halimi
2014-02-01
Full Text Available Objective: To model spatial relationship between climatic conditions and annual parasite incidence (API of malaria in southern part of Sistan&Balouchistan Province of Iran using spatial statistic models . Methods: A geographical weighted regression model was applied for predicting API by 3 climatic factors in order to model the spatial API of malaria in Sistan&Baluchistan Province of Iran. Results: The results indicated that most important climatic factor for explaining API in Sistan&Baluchistan was annual rainfall being of more importance in southern part of study area such as Chabahar, and Nikshar. The temperature and relative humidity are of the second and third priority respectively. The importance of these two climatic factors is higher in northern part of the studied region. The spatial autocorrelation (Moran ’s I for standard residual of applied geographical weighted regression model is -0.022 which indicated no spatial patterns. Conclusions: This model explained only 0.51 of API spatial variation (R2=0.51. Thus, the nonclimatic factors such as socioeconomic, lifestyle and the neighborhood position of this province with Afghanistan, and Pakistan also should be considered in epidemiological survey of malaria in Sistan&Baluchistan.
Affinity functions for modeling glass dissolution rates
Energy Technology Data Exchange (ETDEWEB)
Bourcier, W.L. [Lawrence Livermore National Lab., CA (United States)
1997-07-01
Glass dissolution rates decrease dramatically as glass approach ''saturation'' with respect to the leachate solution. Most repository sites are chosen where water fluxes are minimal, and therefore the waste glass is most likely to dissolve under conditions close to ''saturation''. The key term in the rate expression used to predict glass dissolution rates close to ''saturation'' is the affinity term, which accounts for saturation effects on dissolution rates. Interpretations of recent experimental data on the dissolution behaviour of silicate glasses and silicate minerals indicate the following: 1) simple affinity control does not explain the observed dissolution rate for silicate minerals or glasses; 2) dissolution rates can be significantly modified by dissolved cations even under conditions far from saturation where the affinity term is near unity; 3) the effects of dissolved species such as Al and Si on the dissolution rate vary with pH, temperature, and saturation state; and 4) as temperature is increased, the effect of both pH and temperature on glass and mineral dissolution rates decrease, which strongly suggests a switch in rate control from surface reaction-based to diffusion control. Borosilicate glass dissolution models need to be upgraded to account for these recent experimental observations. (A.C.)
Deep inelastic structure functions in the chiral bag model
International Nuclear Information System (INIS)
Sanjose, V.; Vento, V.; Centro Mixto CSIC/Valencia Univ., Valencia
1989-01-01
We calculate the structure functions for deep inelastic scattering on baryons in the cavity approximation to the chiral bag model. The behavior of these structure functions is analyzed in the Bjorken limit. We conclude that scaling is satisfied, but not Regge behavior. A trivial extension as a parton model can be achieved by introducing the structure function for the pion in a convolution picture. In this extended version of the model not only scaling but also Regge behavior is satisfied. Conclusions are drawn from the comparison of our results with experimental data. (orig.)
Deep inelastic structure functions in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Sanjose, V. (Valencia Univ. (Spain). Dept. de Didactica de las Ciencias Experimentales); Vento, V. (Valencia Univ. (Spain). Dept. de Fisica Teorica; Centro Mixto CSIC/Valencia Univ., Valencia (Spain). Inst. de Fisica Corpuscular)
1989-10-02
We calculate the structure functions for deep inelastic scattering on baryons in the cavity approximation to the chiral bag model. The behavior of these structure functions is analyzed in the Bjorken limit. We conclude that scaling is satisfied, but not Regge behavior. A trivial extension as a parton model can be achieved by introducing the structure function for the pion in a convolution picture. In this extended version of the model not only scaling but also Regge behavior is satisfied. Conclusions are drawn from the comparison of our results with experimental data. (orig.).
A DSM-based framework for integrated function modelling
DEFF Research Database (Denmark)
Eisenbart, Boris; Gericke, Kilian; Blessing, Lucienne T. M.
2017-01-01
an integrated function modelling framework, which specifically aims at relating between the different function modelling perspectives prominently addressed in different disciplines. It uses interlinked matrices based on the concept of DSM and MDM in order to facilitate cross-disciplinary modelling and analysis...... of the functionality of a system. The article further presents the application of the framework based on a product example. Finally, an empirical study in industry is presented. Therein, feedback on the potential of the proposed framework to support interdisciplinary design practice as well as on areas of further...
Composite spectral functions for solving Volterra's population model
International Nuclear Information System (INIS)
Ramezani, M.; Razzaghi, M.; Dehghan, M.
2007-01-01
An approximate method for solving Volterra's population model for population growth of a species in a closed system is proposed. Volterra's model is a nonlinear integro-differential equation, where the integral term represents the effect of toxin. The approach is based upon composite spectral functions approximations. The properties of composite spectral functions consisting of few terms of orthogonal functions are presented and are utilized to reduce the solution of the Volterra's model to the solution of a system of algebraic equations. The method is easy to implement and yields very accurate result
Beretvas, S. Natasha; Walker, Cindy M.
2012-01-01
This study extends the multilevel measurement model to handle testlet-based dependencies. A flexible two-level testlet response model (the MMMT-2 model) for dichotomous items is introduced that permits assessment of differential testlet functioning (DTLF). A distinction is made between this study's conceptualization of DTLF and that of…
BioModels: Content, Features, Functionality, and Use
Juty, N; Ali, R; Glont, M; Keating, S; Rodriguez, N; Swat, MJ; Wimalaratne, SM; Hermjakob, H; Le Novère, N; Laibe, C; Chelliah, V
2015-01-01
BioModels is a reference repository hosting mathematical models that describe the dynamic interactions of biological components at various scales. The resource provides access to over 1,200 models described in literature and over 140,000 models automatically generated from pathway resources. Most model components are cross-linked with external resources to facilitate interoperability. A large proportion of models are manually curated to ensure reproducibility of simulation results. This tutorial presents BioModels' content, features, functionality, and usage. PMID:26225232
Schechter, Clyde B; Near, Aimee M; Jayasekera, Jinani; Chandler, Young; Mandelblatt, Jeanne S
2018-04-01
The Georgetown University-Albert Einstein College of Medicine breast cancer simulation model (Model GE) has evolved over time in structure and function to reflect advances in knowledge about breast cancer, improvements in early detection and treatment technology, and progress in computing resources. This article describes the model and provides examples of model applications. The model is a discrete events microsimulation of single-life histories of women from multiple birth cohorts. Events are simulated in the absence of screening and treatment, and interventions are then applied to assess their impact on population breast cancer trends. The model accommodates differences in natural history associated with estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) biomarkers, as well as conventional breast cancer risk factors. The approach for simulating breast cancer natural history is phenomenological, relying on dates, stage, and age of clinical and screen detection for a tumor molecular subtype without explicitly modeling tumor growth. The inputs to the model are regularly updated to reflect current practice. Numerous technical modifications, including the use of object-oriented programming (C++), and more efficient algorithms, along with hardware advances, have increased program efficiency permitting simulations of large samples. The model results consistently match key temporal trends in US breast cancer incidence and mortality. The model has been used in collaboration with other CISNET models to assess cancer control policies and will be applied to evaluate clinical trial design, recurrence risk, and polygenic risk-based screening.
Meurier, C E
2000-07-01
Human errors are common in clinical practice, but they are under-reported. As a result, very little is known of the types, antecedents and consequences of errors in nursing practice. This limits the potential to learn from errors and to make improvement in the quality and safety of nursing care. The aim of this study was to use an Organizational Accident Model to analyse critical incidents of errors in nursing. Twenty registered nurses were invited to produce a critical incident report of an error (which had led to an adverse event or potentially could have led to an adverse event) they had made in their professional practice and to write down their responses to the error using a structured format. Using Reason's Organizational Accident Model, supplemental information was then collected from five of the participants by means of an individual in-depth interview to explore further issues relating to the incidents they had reported. The detailed analysis of one of the incidents is discussed in this paper, demonstrating the effectiveness of this approach in providing insight into the chain of events which may lead to an adverse event. The case study approach using critical incidents of clinical errors was shown to provide relevant information regarding the interaction of organizational factors, local circumstances and active failures (errors) in producing an adverse or potentially adverse event. It is suggested that more use should be made of this approach to understand how errors are made in practice and to take appropriate preventative measures.
Multinomial-exponential reliability function: a software reliability model
International Nuclear Information System (INIS)
Saiz de Bustamante, Amalio; Saiz de Bustamante, Barbara
2003-01-01
The multinomial-exponential reliability function (MERF) was developed during a detailed study of the software failure/correction processes. Later on MERF was approximated by a much simpler exponential reliability function (EARF), which keeps most of MERF mathematical properties, so the two functions together makes up a single reliability model. The reliability model MERF/EARF considers the software failure process as a non-homogeneous Poisson process (NHPP), and the repair (correction) process, a multinomial distribution. The model supposes that both processes are statistically independent. The paper discusses the model's theoretical basis, its mathematical properties and its application to software reliability. Nevertheless it is foreseen model applications to inspection and maintenance of physical systems. The paper includes a complete numerical example of the model application to a software reliability analysis
Directory of Open Access Journals (Sweden)
Wudi Wei
Full Text Available Hepatitis is a serious public health problem with increasing cases and property damage in Heng County. It is necessary to develop a model to predict the hepatitis epidemic that could be useful for preventing this disease.The autoregressive integrated moving average (ARIMA model and the generalized regression neural network (GRNN model were used to fit the incidence data from the Heng County CDC (Center for Disease Control and Prevention from January 2005 to December 2012. Then, the ARIMA-GRNN hybrid model was developed. The incidence data from January 2013 to December 2013 were used to validate the models. Several parameters, including mean absolute error (MAE, root mean square error (RMSE, mean absolute percentage error (MAPE and mean square error (MSE, were used to compare the performance among the three models.The morbidity of hepatitis from Jan 2005 to Dec 2012 has seasonal variation and slightly rising trend. The ARIMA(0,1,2(1,1,112 model was the most appropriate one with the residual test showing a white noise sequence. The smoothing factor of the basic GRNN model and the combined model was 1.8 and 0.07, respectively. The four parameters of the hybrid model were lower than those of the two single models in the validation. The parameters values of the GRNN model were the lowest in the fitting of the three models.The hybrid ARIMA-GRNN model showed better hepatitis incidence forecasting in Heng County than the single ARIMA model and the basic GRNN model. It is a potential decision-supportive tool for controlling hepatitis in Heng County.
Computational Models for Calcium-Mediated Astrocyte Functions
Directory of Open Access Journals (Sweden)
Tiina Manninen
2018-04-01
Full Text Available The computational neuroscience field has heavily concentrated on the modeling of neuronal functions, largely ignoring other brain cells, including one type of glial cell, the astrocytes. Despite the short history of modeling astrocytic functions, we were delighted about the hundreds of models developed so far to study the role of astrocytes, most often in calcium dynamics, synchronization, information transfer, and plasticity in vitro, but also in vascular events, hyperexcitability, and homeostasis. Our goal here is to present the state-of-the-art in computational modeling of astrocytes in order to facilitate better understanding of the functions and dynamics of astrocytes in the brain. Due to the large number of models, we concentrated on a hundred models that include biophysical descriptions for calcium signaling and dynamics in astrocytes. We categorized the models into four groups: single astrocyte models, astrocyte network models, neuron-astrocyte synapse models, and neuron-astrocyte network models to ease their use in future modeling projects. We characterized the models based on which earlier models were used for building the models and which type of biological entities were described in the astrocyte models. Features of the models were compared and contrasted so that similarities and differences were more readily apparent. We discovered that most of the models were basically generated from a small set of previously published models with small variations. However, neither citations to all the previous models with similar core structure nor explanations of what was built on top of the previous models were provided, which made it possible, in some cases, to have the same models published several times without an explicit intention to make new predictions about the roles of astrocytes in brain functions. Furthermore, only a few of the models are available online which makes it difficult to reproduce the simulation results and further develop
Computational Models for Calcium-Mediated Astrocyte Functions.
Manninen, Tiina; Havela, Riikka; Linne, Marja-Leena
2018-01-01
The computational neuroscience field has heavily concentrated on the modeling of neuronal functions, largely ignoring other brain cells, including one type of glial cell, the astrocytes. Despite the short history of modeling astrocytic functions, we were delighted about the hundreds of models developed so far to study the role of astrocytes, most often in calcium dynamics, synchronization, information transfer, and plasticity in vitro , but also in vascular events, hyperexcitability, and homeostasis. Our goal here is to present the state-of-the-art in computational modeling of astrocytes in order to facilitate better understanding of the functions and dynamics of astrocytes in the brain. Due to the large number of models, we concentrated on a hundred models that include biophysical descriptions for calcium signaling and dynamics in astrocytes. We categorized the models into four groups: single astrocyte models, astrocyte network models, neuron-astrocyte synapse models, and neuron-astrocyte network models to ease their use in future modeling projects. We characterized the models based on which earlier models were used for building the models and which type of biological entities were described in the astrocyte models. Features of the models were compared and contrasted so that similarities and differences were more readily apparent. We discovered that most of the models were basically generated from a small set of previously published models with small variations. However, neither citations to all the previous models with similar core structure nor explanations of what was built on top of the previous models were provided, which made it possible, in some cases, to have the same models published several times without an explicit intention to make new predictions about the roles of astrocytes in brain functions. Furthermore, only a few of the models are available online which makes it difficult to reproduce the simulation results and further develop the models. Thus
Greuter, Marjolein J. E.; Demirel, Erhan; Lew, Jie-Bin; Berkhof, Johannes; Xu, Xiang-Ming; Canfell, Karen; Dekker, Evelien; Meijer, Gerrit A.; Coupé, Veerle M. H.
2016-01-01
We aimed to predict the long-term colorectal cancer incidence, mortality, and colonoscopy demand of the recently implemented Dutch colorectal cancer screening program. The Adenoma and Serrated pathway to Colorectal Cancer model was set up to simulate the Dutch screening program consisting of
Two point function for a simple general relativistic quantum model
Colosi, Daniele
2007-01-01
We study the quantum theory of a simple general relativistic quantum model of two coupled harmonic oscillators and compute the two-point function following a proposal first introduced in the context of loop quantum gravity.
Functional dynamic factor models with application to yield curve forecasting
Hays, Spencer; Shen, Haipeng; Huang, Jianhua Z.
2012-01-01
resulted in a trade-off between goodness of fit and consistency with economic theory. To address this, herein we propose a novel formulation which connects the dynamic factor model (DFM) framework with concepts from functional data analysis: a DFM
Commonsense Psychology and the Functional Requirements of Cognitive Models
National Research Council Canada - National Science Library
Gordon, Andrew S
2005-01-01
In this paper we argue that previous models of cognitive abilities (e.g. memory, analogy) have been constructed to satisfy functional requirements of implicit commonsense psychological theories held by researchers and nonresearchers alike...
Software Design Modelling with Functional Petri Nets | Bakpo ...
African Journals Online (AJOL)
Software Design Modelling with Functional Petri Nets. ... of structured programs and a FPN Software prototype proposed for the conventional programming construct: if-then-else statement. ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT
Importance of predictor variables for models of chemical function
U.S. Environmental Protection Agency — Importance of random forest predictors for all classification models of chemical function. This dataset is associated with the following publication: Isaacs , K., M....
Generalized Functional Linear Models With Semiparametric Single-Index Interactions
Li, Yehua
2010-06-01
We introduce a new class of functional generalized linear models, where the response is a scalar and some of the covariates are functional. We assume that the response depends on multiple covariates, a finite number of latent features in the functional predictor, and interaction between the two. To achieve parsimony, the interaction between the multiple covariates and the functional predictor is modeled semiparametrically with a single-index structure. We propose a two step estimation procedure based on local estimating equations, and investigate two situations: (a) when the basis functions are pre-determined, e.g., Fourier or wavelet basis functions and the functional features of interest are known; and (b) when the basis functions are data driven, such as with functional principal components. Asymptotic properties are developed. Notably, we show that when the functional features are data driven, the parameter estimates have an increased asymptotic variance, due to the estimation error of the basis functions. Our methods are illustrated with a simulation study and applied to an empirical data set, where a previously unknown interaction is detected. Technical proofs of our theoretical results are provided in the online supplemental materials.
Generalized Functional Linear Models With Semiparametric Single-Index Interactions
Li, Yehua; Wang, Naisyin; Carroll, Raymond J.
2010-01-01
We introduce a new class of functional generalized linear models, where the response is a scalar and some of the covariates are functional. We assume that the response depends on multiple covariates, a finite number of latent features in the functional predictor, and interaction between the two. To achieve parsimony, the interaction between the multiple covariates and the functional predictor is modeled semiparametrically with a single-index structure. We propose a two step estimation procedure based on local estimating equations, and investigate two situations: (a) when the basis functions are pre-determined, e.g., Fourier or wavelet basis functions and the functional features of interest are known; and (b) when the basis functions are data driven, such as with functional principal components. Asymptotic properties are developed. Notably, we show that when the functional features are data driven, the parameter estimates have an increased asymptotic variance, due to the estimation error of the basis functions. Our methods are illustrated with a simulation study and applied to an empirical data set, where a previously unknown interaction is detected. Technical proofs of our theoretical results are provided in the online supplemental materials.
FUNCTIONAL MODELLING FOR FAULT DIAGNOSIS AND ITS APPLICATION FOR NPP
Directory of Open Access Journals (Sweden)
MORTEN LIND
2014-12-01
Full Text Available The paper presents functional modelling and its application for diagnosis in nuclear power plants. Functional modelling is defined and its relevance for coping with the complexity of diagnosis in large scale systems like nuclear plants is explained. The diagnosis task is analyzed and it is demonstrated that the levels of abstraction in models for diagnosis must reflect plant knowledge about goals and functions which is represented in functional modelling. Multilevel flow modelling (MFM, which is a method for functional modelling, is introduced briefly and illustrated with a cooling system example. The use of MFM for reasoning about causes and consequences is explained in detail and demonstrated using the reasoning tool, the MFMSuite. MFM applications in nuclear power systems are described by two examples: a PWR; and an FBR reactor. The PWR example show how MFM can be used to model and reason about operating modes. The FBR example illustrates how the modelling development effort can be managed by proper strategies including decomposition and reuse.
Functional Modelling for fault diagnosis and its application for NPP
Energy Technology Data Exchange (ETDEWEB)
Lind, Morten; Zhang, Xin Xin [Dept. of Electrical Engineering, Technical University of Denmark, Kongens Lyngby (Denmark)
2014-12-15
The paper presents functional modelling and its application for diagnosis in nuclear power plants. Functional modelling is defined and its relevance for coping with the complexity of diagnosis in large scale systems like nuclear plants is explained. The diagnosis task is analyzed and it is demonstrated that the levels of abstraction in models for diagnosis must reflect plant knowledge about goals and functions which is represented in functional modelling. Multilevel flow modelling (MFM), which is a method for functional modelling, is introduced briefly and illustrated with a cooling system example. The use of MFM for reasoning about causes and consequences is explained in detail and demonstrated using the reasoning tool, the MFMSuite. MFM applications in nuclear power systems are described by two examples: a PWR; and an FBR reactor. The PWR example show how MFM can be used to model and reason about operating modes. The FBR example illustrates how the modelling development effort can be managed by proper strategies including decomposition and reuse.
Functional Modelling for fault diagnosis and its application for NPP
International Nuclear Information System (INIS)
Lind, Morten; Zhang, Xin Xin
2014-01-01
The paper presents functional modelling and its application for diagnosis in nuclear power plants. Functional modelling is defined and its relevance for coping with the complexity of diagnosis in large scale systems like nuclear plants is explained. The diagnosis task is analyzed and it is demonstrated that the levels of abstraction in models for diagnosis must reflect plant knowledge about goals and functions which is represented in functional modelling. Multilevel flow modelling (MFM), which is a method for functional modelling, is introduced briefly and illustrated with a cooling system example. The use of MFM for reasoning about causes and consequences is explained in detail and demonstrated using the reasoning tool, the MFMSuite. MFM applications in nuclear power systems are described by two examples: a PWR; and an FBR reactor. The PWR example show how MFM can be used to model and reason about operating modes. The FBR example illustrates how the modelling development effort can be managed by proper strategies including decomposition and reuse.
Global sensitivity analysis of computer models with functional inputs
International Nuclear Information System (INIS)
Iooss, Bertrand; Ribatet, Mathieu
2009-01-01
Global sensitivity analysis is used to quantify the influence of uncertain model inputs on the response variability of a numerical model. The common quantitative methods are appropriate with computer codes having scalar model inputs. This paper aims at illustrating different variance-based sensitivity analysis techniques, based on the so-called Sobol's indices, when some model inputs are functional, such as stochastic processes or random spatial fields. In this work, we focus on large cpu time computer codes which need a preliminary metamodeling step before performing the sensitivity analysis. We propose the use of the joint modeling approach, i.e., modeling simultaneously the mean and the dispersion of the code outputs using two interlinked generalized linear models (GLMs) or generalized additive models (GAMs). The 'mean model' allows to estimate the sensitivity indices of each scalar model inputs, while the 'dispersion model' allows to derive the total sensitivity index of the functional model inputs. The proposed approach is compared to some classical sensitivity analysis methodologies on an analytical function. Lastly, the new methodology is applied to an industrial computer code that simulates the nuclear fuel irradiation.
Castanon, Alejandra; Landy, Rebecca; Pesola, Francesca; Windridge, Peter; Sasieni, Peter
2018-01-01
In the next 25 years, the epidemiology of cervical cancer in England, UK, will change: human papillomavirus (HPV) screening will be the primary test for cervical cancer. Additionally, the proportion of women screened regularly is decreasing and women who received the HPV vaccine are due to attend screening for the first time. Therefore, we aimed to estimate how vaccination against HPV, changes to the screening test, and falling screening coverage will affect cervical cancer incidence in England up to 2040. We did a data modelling study that combined results from population modelling of incidence trends, observable data from the individual level with use of a generalised linear model, and microsimulation of unobservable disease states. We estimated age-specific absolute risks of cervical cancer in the absence of screening (derived from individual level data). We used an age period cohort model to estimate birth cohort effects. We multiplied the absolute risks by the age cohort effects to provide absolute risks of cervical cancer for unscreened women in different birth cohorts. We obtained relative risks (RRs) of cervical cancer by screening history (never screened, regularly screened, or lapsed attender) using data from a population-based case-control study for unvaccinated women, and using a microsimulation model for vaccinated women. RRs of primary HPV screening were relative to cytology. We used the proportion of women in each 5-year age group (25-29 years to 75-79 years) and 5-year period (2016-20 to 2036-40) who have a combination of screening and vaccination history, and weighted to estimate the population incidence. The primary outcome was the number of cases and rates per 100 000 women under four scenarios: no changes to current screening coverage or vaccine uptake and HPV primary testing from 2019 (status quo), changing the year in which HPV primary testing is introduced, introduction of the nine-valent vaccine, and changes to cervical screening coverage
Loha, Eskindir; Lindtj?rn, Bernt
2010-01-01
Abstract Background Malaria transmission is complex and is believed to be associated with local climate changes. However, simple attempts to extrapolate malaria incidence rates from averaged regional meteorological conditions have proven unsuccessful. Therefore, the objective of this study was to determine if variations in specific meteorological factors are able to consistently predict P. falciparum malaria incidence at different locations in south Ethiopia. Methods Retrospective data from 4...
Functional linear models for association analysis of quantitative traits.
Fan, Ruzong; Wang, Yifan; Mills, James L; Wilson, Alexander F; Bailey-Wilson, Joan E; Xiong, Momiao
2013-11-01
Functional linear models are developed in this paper for testing associations between quantitative traits and genetic variants, which can be rare variants or common variants or the combination of the two. By treating multiple genetic variants of an individual in a human population as a realization of a stochastic process, the genome of an individual in a chromosome region is a continuum of sequence data rather than discrete observations. The genome of an individual is viewed as a stochastic function that contains both linkage and linkage disequilibrium (LD) information of the genetic markers. By using techniques of functional data analysis, both fixed and mixed effect functional linear models are built to test the association between quantitative traits and genetic variants adjusting for covariates. After extensive simulation analysis, it is shown that the F-distributed tests of the proposed fixed effect functional linear models have higher power than that of sequence kernel association test (SKAT) and its optimal unified test (SKAT-O) for three scenarios in most cases: (1) the causal variants are all rare, (2) the causal variants are both rare and common, and (3) the causal variants are common. The superior performance of the fixed effect functional linear models is most likely due to its optimal utilization of both genetic linkage and LD information of multiple genetic variants in a genome and similarity among different individuals, while SKAT and SKAT-O only model the similarities and pairwise LD but do not model linkage and higher order LD information sufficiently. In addition, the proposed fixed effect models generate accurate type I error rates in simulation studies. We also show that the functional kernel score tests of the proposed mixed effect functional linear models are preferable in candidate gene analysis and small sample problems. The methods are applied to analyze three biochemical traits in data from the Trinity Students Study. © 2013 WILEY
A no extensive statistical model for the nucleon structure function
International Nuclear Information System (INIS)
Trevisan, Luis A.; Mirez, Carlos
2013-01-01
We studied an application of nonextensive thermodynamics to describe the structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and two chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon.
The Potts model and flows. 1. The pair correlation function
International Nuclear Information System (INIS)
Essam, J.W.; Tsallis, C.
1985-01-01
It is shown that the partition function for the lambda-state Potts model with pair-interactions is related to the expected number of integer mod-lambda flows in a percolation model. The relation is generalised to the pair correlation function. The resulting high temperature expansion coefficients are shown to be the flow polynomials of graph theory. An observation of Tsallis and Levy concerning the equivalent transmissivity of a cluster is also proved. (Author) [pt
Longitudinal mixed-effects models for latent cognitive function
van den Hout, Ardo; Fox, Gerardus J.A.; Muniz-Terrera, Graciela
2015-01-01
A mixed-effects regression model with a bent-cable change-point predictor is formulated to describe potential decline of cognitive function over time in the older population. For the individual trajectories, cognitive function is considered to be a latent variable measured through an item response
Correlation function of four spins in the percolation model
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Vladimir S. Dotsenko
2016-10-01
It is known that the four-point functions define the actual fusion rules of a particular model. In this respect, we find that fusion of two spins, of dimension Δσ=596, produce a new channel, in the 4-point function, which is due to the operator with dimension Δ=5/8.
Improved Wave-vessel Transfer Functions by Uncertainty Modelling
DEFF Research Database (Denmark)
Nielsen, Ulrik Dam; Fønss Bach, Kasper; Iseki, Toshio
2016-01-01
This paper deals with uncertainty modelling of wave-vessel transfer functions used to calculate or predict wave-induced responses of a ship in a seaway. Although transfer functions, in theory, can be calculated to exactly reflect the behaviour of the ship when exposed to waves, uncertainty in inp...
Matias, Alessandra B; Taddei, Ulisses T; Duarte, Marcos; Sacco, Isabel C N
2016-04-14
Overall performance, particularly in a very popular sports activity such as running, is typically influenced by the status of the musculoskeletal system and the level of training and conditioning of the biological structures. Any change in the musculoskeletal system's biomechanics, especially in the feet and ankles, will strongly influence the biomechanics of runners, possibly predisposing them to injuries. A thorough understanding of the effects of a therapeutic approach focused on feet biomechanics, on strength and functionality of lower limb muscles will contribute to the adoption of more effective therapeutic and preventive strategies for runners. A randomized, prospective controlled and parallel trial with blind assessment is designed to study the effects of a "ground-up" therapeutic approach focused on the foot-ankle complex as it relates to the incidence of running-related injuries in the lower limbs. One hundred and eleven (111) healthy long-distance runners will be randomly assigned to either a control (CG) or intervention (IG) group. IG runners will participate in a therapeutic exercise protocol for the foot-ankle for 8 weeks, with 1 directly supervised session and 3 remotely supervised sessions per week. After the 8-week period, IG runners will keep exercising for the remaining 10 months of the study, supervised only by web-enabled software three times a week. At baseline, 2 months, 4 months and 12 months, all runners will be assessed for running-related injuries (primary outcome), time for the occurrence of the first injury, foot health and functionality, muscle trophism, intrinsic foot muscle strength, dynamic foot arch strain and lower-limb biomechanics during walking and running (secondary outcomes). This is the first randomized clinical trial protocol to assess the effect of an exercise protocol that was designed specifically for the foot-and-ankle complex on running-related injuries to the lower limbs of long-distance runners. We intend to show
Exploitation of geoinformatics at modelling of functional effects of forest functions
International Nuclear Information System (INIS)
Sitko, R.
2005-01-01
From point of view of space modelling geoinformatics has wide application in group of ecologic function of forest because they directly depend on natural conditions of site. A causa de cy modelling application was realised on the territory of TANAP (Tatras National Park), West Tatras, in the part Liptovske Kopy. The size of this territory is about 4,900 hectares and forests there subserve the first of all significant ecological functions, what are soil protection from erosion, water management, and anti-avalanche function. Of environmental functions they have recreational role of the forest and function of nature protection. Anti-avalanche and anti-erosion function of forest is evaluated in this presentation
Features of Functioning the Integrated Building Thermal Model
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Morozov Maxim N.
2017-01-01
Full Text Available A model of the building heating system, consisting of energy source, a distributed automatic control system, elements of individual heating unit and heating system is designed. Application Simulink of mathematical package Matlab is selected as a platform for the model. There are the specialized application Simscape libraries in aggregate with a wide range of Matlab mathematical tools allow to apply the “acausal” modeling concept. Implementation the “physical” representation of the object model gave improving the accuracy of the models. Principle of operation and features of the functioning of the thermal model is described. The investigations of building cooling dynamics were carried out.
DEFF Research Database (Denmark)
Soerjomataram, Isabelle; de Vries, Esther; Engholm, Gerda
2010-01-01
Prevent v.3.01 to assess the changes in incidence as a result of risk factor changes. Incidence of lung and breast cancer until 2050 was predicted under two scenarios: ideal (total elimination of smoking and reduction of alcohol intake to maximum 1units/d for women) and optimistic (decreasing prevalence......PURPOSE: Among the known risk factors, smoking is clearly related to the incidence of lung cancer and alcohol consumption is to breast cancer. In this manuscript we modelled the potential benefits of reductions in smoking or alcohol prevalence for the burden of these cancers. METHOD: We used...... of risk factors because of a 10% increase in cigarette and alcohol beverage price, repeated every 5years). Danish data from the household surveys, cancer registration and Eurostat were used. RESULTS: Up to 49% less new lung cancer cases can be expected in 2050 if smoking were to be completely eliminated...
DEFF Research Database (Denmark)
Kehres, Jan; Pedersen, Thomas; Masini, Federico
2016-01-01
at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles.......The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing......-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments...
Kehres, Jan; Pedersen, Thomas; Masini, Federico; Andreasen, Jens Wenzel; Nielsen, Martin Meedom; Diaz, Ana; Nielsen, Jane Hvolbæk; Hansen, Ole
2016-01-01
The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles. PMID:26917133
Kehres, Jan; Pedersen, Thomas; Masini, Federico; Andreasen, Jens Wenzel; Nielsen, Martin Meedom; Diaz, Ana; Nielsen, Jane Hvolbæk; Hansen, Ole; Chorkendorff, Ib
2016-03-01
The design, fabrication and performance of a novel and highly sensitive micro-reactor device for performing in situ grazing-incidence X-ray scattering experiments of model catalyst systems is presented. The design of the reaction chamber, etched in silicon on insulator (SIO), permits grazing-incidence small-angle X-ray scattering (GISAXS) in transmission through 10 µm-thick entrance and exit windows by using micro-focused beams. An additional thinning of the Pyrex glass reactor lid allows simultaneous acquisition of the grazing-incidence wide-angle X-ray scattering (GIWAXS). In situ experiments at synchrotron facilities are performed utilizing the micro-reactor and a designed transportable gas feed and analysis system. The feasibility of simultaneous in situ GISAXS/GIWAXS experiments in the novel micro-reactor flow cell was confirmed with CO oxidation over mass-selected Ru nanoparticles.
Ab initio derivation of model energy density functionals
International Nuclear Information System (INIS)
Dobaczewski, Jacek
2016-01-01
I propose a simple and manageable method that allows for deriving coupling constants of model energy density functionals (EDFs) directly from ab initio calculations performed for finite fermion systems. A proof-of-principle application allows for linking properties of finite nuclei, determined by using the nuclear nonlocal Gogny functional, to the coupling constants of the quasilocal Skyrme functional. The method does not rely on properties of infinite fermion systems but on the ab initio calculations in finite systems. It also allows for quantifying merits of different model EDFs in describing the ab initio results. (letter)
Joint Modelling of Structural and Functional Brain Networks
DEFF Research Database (Denmark)
Andersen, Kasper Winther; Herlau, Tue; Mørup, Morten
-parametric Bayesian network model which allows for joint modelling and integration of multiple networks. We demonstrate the model’s ability to detect vertices that share structure across networks jointly in functional MRI (fMRI) and diffusion MRI (dMRI) data. Using two fMRI and dMRI scans per subject, we establish...
Constructing rule-based models using the belief functions framework
Almeida, R.J.; Denoeux, T.; Kaymak, U.; Greco, S.; Bouchon-Meunier, B.; Coletti, G.; Fedrizzi, M.; Matarazzo, B.; Yager, R.R.
2012-01-01
Abstract. We study a new approach to regression analysis. We propose a new rule-based regression model using the theoretical framework of belief functions. For this purpose we use the recently proposed Evidential c-means (ECM) to derive rule-based models solely from data. ECM allocates, for each
PSA Model Improvement Using Maintenance Rule Function Mapping
Energy Technology Data Exchange (ETDEWEB)
Seo, Mi Ro [KHNP-CRI, Nuclear Safety Laboratory, Daejeon (Korea, Republic of)
2011-10-15
The Maintenance Rule (MR) program, in nature, is a performance-based program. Therefore, the risk information derived from the Probabilistic Safety Assessment model is introduced into the MR program during the Safety Significance determination and Performance Criteria selection processes. However, this process also facilitates the determination of the vulnerabilities in currently utilized PSA models and offers means of improving them. To find vulnerabilities in an existing PSA model, an initial review determines whether the safety-related MR functions are included in the PSA model. Because safety-related MR functions are related to accident prevention and mitigation, it is generally necessary for them to be included in the PSA model. In the process of determining the safety significance of each functions, quantitative risk importance levels are determined through a process known as PSA model basic event mapping to MR functions. During this process, it is common for some inadequate and overlooked models to be uncovered. In this paper, the PSA model and the MR program of Wolsong Unit 1 were used as references
NJL-jet model for quark fragmentation functions
International Nuclear Information System (INIS)
Ito, T.; Bentz, W.; Cloeet, I. C.; Thomas, A. W.; Yazaki, K.
2009-01-01
A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented in an effective quark theory. Concentrating on the pion fragmentation function, we first explain why the elementary (lowest order) fragmentation process q→qπ is completely inadequate to describe the empirical data, although the crossed process π→qq describes the quark distribution functions in the pion reasonably well. Taking into account cascadelike processes in a generalized jet-model approach, we then show that the momentum and isospin sum rules can be satisfied naturally, without the introduction of ad hoc parameters. We present results for the Nambu-Jona-Lasinio (NJL) model in the invariant mass regularization scheme and compare them with the empirical parametrizations. We argue that the NJL-jet model, developed herein, provides a useful framework with which to calculate the fragmentation functions in an effective chiral quark theory.
Apply Functional Modelling to Consequence Analysis in Supervision Systems
DEFF Research Database (Denmark)
Zhang, Xinxin; Lind, Morten; Gola, Giulio
2013-01-01
This paper will first present the purpose and goals of applying functional modelling approach to consequence analysis by adopting Multilevel Flow Modelling (MFM). MFM Models describe a complex system in multiple abstraction levels in both means-end dimension and whole-part dimension. It contains...... consequence analysis to practical or online applications in supervision systems. It will also suggest a multiagent solution as the integration architecture for developing tools to facilitate the utilization results of functional consequence analysis. Finally a prototype of the multiagent reasoning system...... causal relations between functions and goals. A rule base system can be developed to trace the causal relations and perform consequence propagations. This paper will illustrate how to use MFM for consequence reasoning by using rule base technology and describe the challenges for integrating functional...
Density Functional Theory and Materials Modeling at Atomistic Length Scales
Directory of Open Access Journals (Sweden)
Swapan K. Ghosh
2002-04-01
Full Text Available Abstract: We discuss the basic concepts of density functional theory (DFT as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT consists of Boltzmann type distributions, both corresponding to a system of noninteracting particles in the field of a density-dependent effective potential, the exact functional form of which is unknown. One therefore approximates the exchange-correlation potential for quantum systems and the excess free energy density functional or the direct correlation functions for classical systems. Illustrative applications of quantum DFT to microscopic modeling of molecular interaction and that of classical DFT to a mesoscopic modeling of soft condensed matter systems are highlighted.
Evaluation-Function-based Model-free Adaptive Fuzzy Control
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Agus Naba
2016-12-01
Full Text Available Designs of adaptive fuzzy controllers (AFC are commonly based on the Lyapunov approach, which requires a known model of the controlled plant. They need to consider a Lyapunov function candidate as an evaluation function to be minimized. In this study these drawbacks were handled by designing a model-free adaptive fuzzy controller (MFAFC using an approximate evaluation function defined in terms of the current state, the next state, and the control action. MFAFC considers the approximate evaluation function as an evaluative control performance measure similar to the state-action value function in reinforcement learning. The simulation results of applying MFAFC to the inverted pendulum benchmark veriﬁed the proposed scheme’s efficacy.
Model Penentuan Nilai Target Functional Requirement Berbasis Utilitas
Directory of Open Access Journals (Sweden)
Cucuk Nur Rosyidi
2012-01-01
Full Text Available In a product design and development process, a designer faces a problem to decide functional requirement (FR target values. That decision is made under a risk since it is conducted in the early design phase using incomplete information. Utility function can be used to reflect the decision maker attitude towards the risk in making such decision. In this research, we develop a utility-based model to determine FR target values using quadratic utility function and information from Quality Function Deployment (QFD. A pencil design is used as a numerical example using quadratic utility function for each FR. The model can be applied for balancing customer and designer interest in determining FR target values.
Modelling the Impact of Soil Management on Soil Functions
Vogel, H. J.; Weller, U.; Rabot, E.; Stößel, B.; Lang, B.; Wiesmeier, M.; Urbanski, L.; Wollschläger, U.
2017-12-01
Due to an increasing soil loss and an increasing demand for food and energy there is an enormous pressure on soils as the central resource for agricultural production. Besides the importance of soils for biomass production there are other essential soil functions, i.e. filter and buffer for water, carbon sequestration, provision and recycling of nutrients, and habitat for biological activity. All these functions have a direct feed back to biogeochemical cycles and climate. To render agricultural production efficient and sustainable we need to develop model tools that are capable to predict quantitatively the impact of a multitude of management measures on these soil functions. These functions are considered as emergent properties produced by soils as complex systems. The major challenge is to handle the multitude of physical, chemical and biological processes interacting in a non-linear manner. A large number of validated models for specific soil processes are available. However, it is not possible to simulate soil functions by coupling all the relevant processes at the detailed (i.e. molecular) level where they are well understood. A new systems perspective is required to evaluate the ensemble of soil functions and their sensitivity to external forcing. Another challenge is that soils are spatially heterogeneous systems by nature. Soil processes are highly dependent on the local soil properties and, hence, any model to predict soil functions needs to account for the site-specific conditions. For upscaling towards regional scales the spatial distribution of functional soil types need to be taken into account. We propose a new systemic model approach based on a thorough analysis of the interactions between physical, chemical and biological processes considering their site-specific characteristics. It is demonstrated for the example of soil compaction and the recovery of soil structure, water capacity and carbon stocks as a result of plant growth and biological
String beta function equations from c=1 matrix model
Dhar, A; Wadia, S R; Dhar, Avinash; Mandal, Gautam; Wadia, Spenta R
1995-01-01
We derive the \\sigma-model tachyon \\beta-function equation of 2-dimensional string theory, in the background of flat space and linear dilaton, working entirely within the c=1 matrix model. The tachyon \\beta-function equation is satisfied by a \\underbar{nonlocal} and \\underbar{nonlinear} combination of the (massless) scalar field of the matrix model. We discuss the possibility of describing the `discrete states' as well as other possible gravitational and higher tensor backgrounds of 2-dimensional string theory within the c=1 matrix model. We also comment on the realization of the W-infinity symmetry of the matrix model in the string theory. The present work reinforces the viewpoint that a nonlocal (and nonlinear) transform is required to extract the space-time physics of 2-dimensional string theory from the c=1 matrix model.
Partially linear varying coefficient models stratified by a functional covariate
Maity, Arnab
2012-10-01
We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric component and a profiling estimator of the parametric component of the model and derive their asymptotic properties. Specifically, we show the consistency of the nonparametric functional estimates and derive the asymptotic expansion of the estimates of the parametric component. We illustrate the performance of our methodology using a simulation study and a real data application.
Zeros of the partition function for some generalized Ising models
International Nuclear Information System (INIS)
Dunlop, F.
1981-01-01
The author considers generalized Ising Models with two and four body interactions in a complex external field h such that Re h>=mod(Im h) + C, where C is an explicit function of the interaction parameters. The partition function Z(h) is then shown to satisfy mod(Z(h))>=Z(c), so that the pressure is analytic in h inside the given region. The method is applied to specific examples: the gauge invariant Ising Model, and the Widom Rowlinson model on the lattice. (Auth.)
Directory of Open Access Journals (Sweden)
Yumin Zhou
2014-03-01
Full Text Available BACKGROUND: Biomass smoke is associated with the risk of chronic obstructive pulmonary disease (COPD, but few studies have elaborated approaches to reduce the risk of COPD from biomass burning. The purpose of this study was to determine whether improved cooking fuels and ventilation have effects on pulmonary function and the incidence of COPD. METHODS AND FINDINGS: A 9-y prospective cohort study was conducted among 996 eligible participants aged at least 40 y from November 1, 2002, through November 30, 2011, in 12 villages in southern China. Interventions were implemented starting in 2002 to improve kitchen ventilation (by providing support and instruction for improving biomass stoves or installing exhaust fans and to promote the use of clean fuels (i.e., biogas instead of biomass for cooking (by providing support and instruction for installing household biogas digesters; questionnaire interviews and spirometry tests were performed in 2005, 2008, and 2011. That the interventions improved air quality was confirmed via measurements of indoor air pollutants (i.e., SO₂, CO, CO₂, NO₂, and particulate matter with an aerodynamic diameter of 10 µm or less in a randomly selected subset of the participants' homes. Annual declines in lung function and COPD incidence were compared between those who took up one, both, or neither of the interventions. Use of clean fuels and improved ventilation were associated with a reduced decline in forced expiratory volume in 1 s (FEV₁: decline in FEV₁ was reduced by 12 ml/y (95% CI, 4 to 20 ml/y and 13 ml/y (95% CI, 4 to 23 ml/y in those who used clean fuels and improved ventilation, respectively, compared to those who took up neither intervention, after adjustment for confounders. The combined improvements of use of clean fuels and improved ventilation had the greatest favorable effects on the decline in FEV₁, with a slowing of 16 ml/y (95% CI, 9 to 23 ml/y. The longer the duration of improved fuel use and
Prokhorov, Alexander; Prokhorova, Nina I
2012-11-20
We applied the bidirectional reflectance distribution function (BRDF) model consisting of diffuse, quasi-specular, and glossy components to the Monte Carlo modeling of spectral effective emissivities for nonisothermal cavities. A method for extension of a monochromatic three-component (3C) BRDF model to a continuous spectral range is proposed. The initial data for this method are the BRDFs measured in the plane of incidence at a single wavelength and several incidence angles and directional-hemispherical reflectance measured at one incidence angle within a finite spectral range. We proposed the Monte Carlo algorithm for calculation of spectral effective emissivities for nonisothermal cavities whose internal surface is described by the wavelength-dependent 3C BRDF model. The results obtained for a cylindroconical nonisothermal cavity are discussed and compared with results obtained using the conventional specular-diffuse model.
Functional State Modelling of Cultivation Processes: Dissolved Oxygen Limitation State
Directory of Open Access Journals (Sweden)
Olympia Roeva
2015-04-01
Full Text Available A new functional state, namely dissolved oxygen limitation state for both bacteria Escherichia coli and yeast Saccharomyces cerevisiae fed-batch cultivation processes is presented in this study. Functional state modelling approach is applied to cultivation processes in order to overcome the main disadvantages of using global process model, namely complex model structure and a big number of model parameters. Alongwith the newly introduced dissolved oxygen limitation state, second acetate production state and first acetate production state are recognized during the fed-batch cultivation of E. coli, while mixed oxidative state and first ethanol production state are recognized during the fed-batch cultivation of S. cerevisiae. For all mentioned above functional states both structural and parameter identification is here performed based on experimental data of E. coli and S. cerevisiae fed-batch cultivations.
Assessment of tropospheric delay mapping function models in Egypt: Using PTD database model
Abdelfatah, M. A.; Mousa, Ashraf E.; El-Fiky, Gamal S.
2018-06-01
For space geodetic measurements, estimates of tropospheric delays are highly correlated with site coordinates and receiver clock biases. Thus, it is important to use the most accurate models for the tropospheric delay to reduce errors in the estimates of the other parameters. Both the zenith delay value and mapping function should be assigned correctly to reduce such errors. Several mapping function models can treat the troposphere slant delay. The recent models were not evaluated for the Egyptian local climate conditions. An assessment of these models is needed to choose the most suitable one. The goal of this paper is to test the quality of global mapping function which provides high consistency with precise troposphere delay (PTD) mapping functions. The PTD model is derived from radiosonde data using ray tracing, which consider in this paper as true value. The PTD mapping functions were compared, with three recent total mapping functions model and another three separate dry and wet mapping function model. The results of the research indicate that models are very close up to zenith angle 80°. Saastamoinen and 1/cos z model are behind accuracy. Niell model is better than VMF model. The model of Black and Eisner is a good model. The results also indicate that the geometric range error has insignificant effect on slant delay and the fluctuation of azimuth anti-symmetric is about 1%.
Modelling the bidirectional reflectance distribution functions (BRDF of sea areas polluted by oil
Directory of Open Access Journals (Sweden)
Zbigniew Otremba
2004-12-01
Full Text Available The paper discusses the possibilities of modelling the bi-directional reflectance distribution function (BRDF in sea areas polluted by oil. Three sea basin models are considered: a coastal one free of oil, one polluted by an oil film and one polluted by an oil emulsion. The following concentrations of oil were compared: for the film, 1 cm3 of oil per 1 m2 water surface, for the emulsion 1 cm3 of oil in 1 m3 of water. The optical properties of Romashkino crude oil were taken into consideration, as were various angles of incident solar light. The conversion of BRDFs into a directional distribution of the optical contrast of polluted areas is demonstrated.
Cheung, Li C; Pan, Qing; Hyun, Noorie; Schiffman, Mark; Fetterman, Barbara; Castle, Philip E; Lorey, Thomas; Katki, Hormuzd A
2017-09-30
For cost-effectiveness and efficiency, many large-scale general-purpose cohort studies are being assembled within large health-care providers who use electronic health records. Two key features of such data are that incident disease is interval-censored between irregular visits and there can be pre-existing (prevalent) disease. Because prevalent disease is not always immediately diagnosed, some disease diagnosed at later visits are actually undiagnosed prevalent disease. We consider prevalent disease as a point mass at time zero for clinical applications where there is no interest in time of prevalent disease onset. We demonstrate that the naive Kaplan-Meier cumulative risk estimator underestimates risks at early time points and overestimates later risks. We propose a general family of mixture models for undiagnosed prevalent disease and interval-censored incident disease that we call prevalence-incidence models. Parameters for parametric prevalence-incidence models, such as the logistic regression and Weibull survival (logistic-Weibull) model, are estimated by direct likelihood maximization or by EM algorithm. Non-parametric methods are proposed to calculate cumulative risks for cases without covariates. We compare naive Kaplan-Meier, logistic-Weibull, and non-parametric estimates of cumulative risk in the cervical cancer screening program at Kaiser Permanente Northern California. Kaplan-Meier provided poor estimates while the logistic-Weibull model was a close fit to the non-parametric. Our findings support our use of logistic-Weibull models to develop the risk estimates that underlie current US risk-based cervical cancer screening guidelines. Published 2017. This article has been contributed to by US Government employees and their work is in the public domain in the USA. Published 2017. This article has been contributed to by US Government employees and their work is in the public domain in the USA.
Embedded systems development from functional models to implementations
Zeng, Haibo; Natale, Marco; Marwedel, Peter
2014-01-01
This book offers readers broad coverage of techniques to model, verify and validate the behavior and performance of complex distributed embedded systems. The authors attempt to bridge the gap between the three disciplines of model-based design, real-time analysis and model-driven development, for a better understanding of the ways in which new development flows can be constructed, going from system-level modeling to the correct and predictable generation of a distributed implementation, leveraging current and future research results. Describes integration of heterogeneous models; Discusses synthesis of task model implementations and code implementations; Compares model-based design vs. model-driven approaches; Explains how to enforce correctness by construction in the functional and time domains; Includes optimization techniques for control performance.
Modeling Functional Neuroanatomy for an Anatomy Information System
Niggemann, Jörg M.; Gebert, Andreas; Schulz, Stefan
2008-01-01
Objective Existing neuroanatomical ontologies, databases and information systems, such as the Foundational Model of Anatomy (FMA), represent outgoing connections from brain structures, but cannot represent the “internal wiring” of structures and as such, cannot distinguish between different independent connections from the same structure. Thus, a fundamental aspect of Neuroanatomy, the functional pathways and functional systems of the brain such as the pupillary light reflex system, is not adequately represented. This article identifies underlying anatomical objects which are the source of independent connections (collections of neurons) and uses these as basic building blocks to construct a model of functional neuroanatomy and its functional pathways. Design The basic representational elements of the model are unnamed groups of neurons or groups of neuron segments. These groups, their relations to each other, and the relations to the objects of macroscopic anatomy are defined. The resulting model can be incorporated into the FMA. Measurements The capabilities of the presented model are compared to the FMA and the Brain Architecture Management System (BAMS). Results Internal wiring as well as functional pathways can correctly be represented and tracked. Conclusion This model bridges the gap between representations of single neurons and their parts on the one hand and representations of spatial brain structures and areas on the other hand. It is capable of drawing correct inferences on pathways in a nervous system. The object and relation definitions are related to the Open Biomedical Ontology effort and its relation ontology, so that this model can be further developed into an ontology of neuronal functional systems. PMID:18579841
Quark fragmentation functions in NJL-jet model
Bentz, Wolfgang; Matevosyan, Hrayr; Thomas, Anthony
2014-09-01
We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. Supported by Grant in Aid for Scientific Research, Japanese Ministry of Education, Culture, Sports, Science and Technology, Project No. 20168769.
Functionally unidimensional item response models for multivariate binary data
DEFF Research Database (Denmark)
Ip, Edward; Molenberghs, Geert; Chen, Shyh-Huei
2013-01-01
The problem of fitting unidimensional item response models to potentially multidimensional data has been extensively studied. The focus of this article is on response data that have a strong dimension but also contain minor nuisance dimensions. Fitting a unidimensional model to such multidimensio......The problem of fitting unidimensional item response models to potentially multidimensional data has been extensively studied. The focus of this article is on response data that have a strong dimension but also contain minor nuisance dimensions. Fitting a unidimensional model...... to such multidimensional data is believed to result in ability estimates that represent a combination of the major and minor dimensions. We conjecture that the underlying dimension for the fitted unidimensional model, which we call the functional dimension, represents a nonlinear projection. In this article we investigate...... tool. An example regarding a construct of desire for physical competency is used to illustrate the functional unidimensional approach....
Cremer, Paul C; Zhang, Yiran; Alu, Maria; Rodriguez, L Leonardo; Lindman, Brian R; Zajarias, Alan; Hahn, Rebecca T; Lerakis, Stamatios; Malaisrie, S Chris; Douglas, Pamela S; Pibarot, Philippe; Svensson, Lars G; Leon, Martin B; Jaber, Wael A
2018-05-08
In patients randomized to transcatheter or surgical aortic valve replacement (TAVR, SAVR), we sought to determine whether SAVR is associated with worsening right ventricular (RV) function and whether RV deterioration is associated with mortality. In 1376 patients from PARTNERIIA with paired baseline and 30-day core lab echocardiograms, worsening RV function was defined as decline by at least one grade from baseline to 30 days. Our primary outcome was all-cause mortality from 30 days to 2 years. Among 744 patients with TAVR, 62 (8.3%) had worsening RV function, compared with 156 of 632 patients with SAVR (24.7%) (P < 0.0001). In a multivariable model, SAVR [odds ratio (OR) 4.05, 95% confidence interval (CI) 2.55-6.44], a dilated RV (OR 2.38, 95% CI 1.37-4.14), and more than mild tricuspid regurgitation (TR) (OR 2.58, 95% CI 1.25-5.33) were associated with worsening RV function. There were 169 deaths, and patients with worsening RV function had higher all-cause mortality [hazard ratio (HR) 1.98, 95% CI 1.40-2.79]. This association remained robust after adjusting for clinical and echocardiographic variables. Among patients with worsening RV function, there was no mortality difference between TAVR and SAVR (HR 1.16, 95% CI 0.61-2.18). The development of moderate or severe RV dysfunction from baseline normal RV function conferred the worst prognosis (HR 2.87, 95% CI 1.40-5.89). After aortic valve replacement, worsening RV function is more common in patients with baseline RV dilation, more than mild TR, and in patients treated with SAVR. Worsening RV function and the magnitude of deterioration have important prognostic implications.
Towards refactoring the Molecular Function Ontology with a UML profile for function modeling.
Burek, Patryk; Loebe, Frank; Herre, Heinrich
2017-10-04
Gene Ontology (GO) is the largest resource for cataloging gene products. This resource grows steadily and, naturally, this growth raises issues regarding the structure of the ontology. Moreover, modeling and refactoring large ontologies such as GO is generally far from being simple, as a whole as well as when focusing on certain aspects or fragments. It seems that human-friendly graphical modeling languages such as the Unified Modeling Language (UML) could be helpful in connection with these tasks. We investigate the use of UML for making the structural organization of the Molecular Function Ontology (MFO), a sub-ontology of GO, more explicit. More precisely, we present a UML dialect, called the Function Modeling Language (FueL), which is suited for capturing functions in an ontologically founded way. FueL is equipped, among other features, with language elements that arise from studying patterns of subsumption between functions. We show how to use this UML dialect for capturing the structure of molecular functions. Furthermore, we propose and discuss some refactoring options concerning fragments of MFO. FueL enables the systematic, graphical representation of functions and their interrelations, including making information explicit that is currently either implicit in MFO or is mainly captured in textual descriptions. Moreover, the considered subsumption patterns lend themselves to the methodical analysis of refactoring options with respect to MFO. On this basis we argue that the approach can increase the comprehensibility of the structure of MFO for humans and can support communication, for example, during revision and further development.
Driver steering model for closed-loop steering function analysis
Bolia, Pratiksh; Weiskircher, Thomas; Müller, Steffen
2014-05-01
In this paper, a two level preview driver steering control model for the use in numerical vehicle dynamics simulation is introduced. The proposed model is composed of cascaded control loops: The outer loop is the path following layer based on potential field framework. The inner loop tries to capture the driver's physical behaviour. The proposed driver model allows easy implementation of different driving situations to simulate a wide range of different driver types, moods and vehicle types. The expediency of the proposed driver model is shown with the help of developed driver steering assist (DSA) function integrated with a conventional series production (Electric Power steering System with rack assist servo unit) system. With the help of the DSA assist function, the driver is prevented from over saturating the front tyre forces and loss of stability and controllability during cornering. The simulation results show different driver reactions caused by the change in the parameters or properties of the proposed driver model if the DSA assist function is activated. Thus, the proposed driver model is useful for the advanced driver steering and vehicle stability assist function evaluation in the early stage of vehicle dynamics handling and stability evaluation.
Spatial and functional modeling of carnivore and insectivore molariform teeth.
Evans, Alistair R; Sanson, Gordon D
2006-06-01
The interaction between the two main competing geometric determinants of teeth (the geometry of function and the geometry of occlusion) were investigated through the construction of three-dimensional spatial models of several mammalian tooth forms (carnassial, insectivore premolar, zalambdodont, dilambdodont, and tribosphenic). These models aim to emulate the shape and function of mammalian teeth. The geometric principles of occlusion relating to single- and double-crested teeth are reviewed. Function was considered using engineering principles that relate tooth shape to function. Substantial similarity between the models and mammalian teeth were achieved. Differences between the two indicate the influence of tooth strength, geometric relations between upper and lower teeth (including the presence of the protocone), and wear on tooth morphology. The concept of "autocclusion" is expanded to include any morphological features that ensure proper alignment of cusps on the same tooth and other teeth in the tooth row. It is concluded that the tooth forms examined are auto-aligning, and do not require additional morphological guides for correct alignment. The model of therian molars constructed by Crompton and Sita-Lumsden ([1970] Nature 227:197-199) is reconstructed in 3D space to show that their hypothesis of crest geometry is erroneous, and that their model is a special case of a more general class of models. (c) 2004 Wiley-Liss, Inc.
Correlation functions of heisenberg-mattis model in one dimension
International Nuclear Information System (INIS)
Azeeem, W.
1991-01-01
The technique of real-space renormalization to the dynamics of Heisenberg-Mattis model, which represents a random magnetic system with competing ferromagnetic and antiferromagnetic interactions has been applied. The renormalization technique, which has been in use for calculating density of states, is extended to calculate dynamical response function from momentum energy dependent Green's functions. Our numerical results on density of states and structure function of one-dimensional Heisenberg-Mattis model come out to be in good agreement with computer simulation results. The numerical scheme worked out in this thesis has the advantage that it can also provide a complete map of momentum and energy dependence of the structure function. (author)
A unified wall function for compressible turbulence modelling
Ong, K. C.; Chan, A.
2018-05-01
Turbulence modelling near the wall often requires a high mesh density clustered around the wall and the first cells adjacent to the wall to be placed in the viscous sublayer. As a result, the numerical stability is constrained by the smallest cell size and hence requires high computational overhead. In the present study, a unified wall function is developed which is valid for viscous sublayer, buffer sublayer and inertial sublayer, as well as including effects of compressibility, heat transfer and pressure gradient. The resulting wall function applies to compressible turbulence modelling for both isothermal and adiabatic wall boundary conditions with the non-zero pressure gradient. Two simple wall function algorithms are implemented for practical computation of isothermal and adiabatic wall boundary conditions. The numerical results show that the wall function evaluates the wall shear stress and turbulent quantities of wall adjacent cells at wide range of non-dimensional wall distance and alleviate the number and size of cells required.
Functional form diagnostics for Cox's proportional hazards model.
León, Larry F; Tsai, Chih-Ling
2004-03-01
We propose a new type of residual and an easily computed functional form test for the Cox proportional hazards model. The proposed test is a modification of the omnibus test for testing the overall fit of a parametric regression model, developed by Stute, González Manteiga, and Presedo Quindimil (1998, Journal of the American Statistical Association93, 141-149), and is based on what we call censoring consistent residuals. In addition, we develop residual plots that can be used to identify the correct functional forms of covariates. We compare our test with the functional form test of Lin, Wei, and Ying (1993, Biometrika80, 557-572) in a simulation study. The practical application of the proposed residuals and functional form test is illustrated using both a simulated data set and a real data set.
Leukocyte and platelet depletion improves blood flow and function in a renal transplant model.
Yates, Phillip J; Hosgood, Sarah A; Nicholson, Michael L
2012-01-01
Donation after cardiac death (DCD) donors are an important source of organs for transplantation. Due to warm and cold ischemic injury, DCD kidneys undergo a significant reperfusion insult when transplanted. This is manifested clinically as a high incidence of delayed graft function (DGF) and primary non-function (PNF). The importance of leukocytes in the generation of reperfusion injury is pivotal. Using an ex vivo porcine model of kidney transplantation, the effects of reperfusion with leukocyte and platelet depleted blood (LDB) and whole blood (WB) on renal blood flow and function were compared. Hemodynamic measurements were recorded, and biochemical, hematological, and histologic samples taken at set time-points. Reperfusion with LDB improved renal blood flow significantly compared with WB reperfusion. In addition, there was a significant improvement in creatinine clearance and renal oxygen consumption, but not fractional excretion of sodium, acid-base homeostasis, urinary nitric oxide (NO), or 8-isoprostane levels. This study represents a good model for the initial reperfusion period in renal transplantation. Improvement in only some functional markers and neither urinary NO nor 8-isoprostane levels indicates that improved blood flow alone is not sufficient to reverse the severe ischemic insult endured by DCD kidneys. Copyright © 2012 Elsevier Inc. All rights reserved.
Conserved Functional Motifs and Homology Modeling to Predict Hidden Moonlighting Functional Sites
Wong, Aloysius Tze; Gehring, Christoph A; Irving, Helen R.
2015-01-01
Moonlighting functional centers within proteins can provide them with hitherto unrecognized functions. Here, we review how hidden moonlighting functional centers, which we define as binding sites that have catalytic activity or regulate protein function in a novel manner, can be identified using targeted bioinformatic searches. Functional motifs used in such searches include amino acid residues that are conserved across species and many of which have been assigned functional roles based on experimental evidence. Molecules that were identified in this manner seeking cyclic mononucleotide cyclases in plants are used as examples. The strength of this computational approach is enhanced when good homology models can be developed to test the functionality of the predicted centers in silico, which, in turn, increases confidence in the ability of the identified candidates to perform the predicted functions. Computational characterization of moonlighting functional centers is not diagnostic for catalysis but serves as a rapid screening method, and highlights testable targets from a potentially large pool of candidates for subsequent in vitro and in vivo experiments required to confirm the functionality of the predicted moonlighting centers.
Conserved Functional Motifs and Homology Modeling to Predict Hidden Moonlighting Functional Sites
Wong, Aloysius Tze
2015-06-09
Moonlighting functional centers within proteins can provide them with hitherto unrecognized functions. Here, we review how hidden moonlighting functional centers, which we define as binding sites that have catalytic activity or regulate protein function in a novel manner, can be identified using targeted bioinformatic searches. Functional motifs used in such searches include amino acid residues that are conserved across species and many of which have been assigned functional roles based on experimental evidence. Molecules that were identified in this manner seeking cyclic mononucleotide cyclases in plants are used as examples. The strength of this computational approach is enhanced when good homology models can be developed to test the functionality of the predicted centers in silico, which, in turn, increases confidence in the ability of the identified candidates to perform the predicted functions. Computational characterization of moonlighting functional centers is not diagnostic for catalysis but serves as a rapid screening method, and highlights testable targets from a potentially large pool of candidates for subsequent in vitro and in vivo experiments required to confirm the functionality of the predicted moonlighting centers.
Bread dough rheology: Computing with a damage function model
Tanner, Roger I.; Qi, Fuzhong; Dai, Shaocong
2015-01-01
We describe an improved damage function model for bread dough rheology. The model has relatively few parameters, all of which can easily be found from simple experiments. Small deformations in the linear region are described by a gel-like power-law memory function. A set of large non-reversing deformations - stress relaxation after a step of shear, steady shearing and elongation beginning from rest, and biaxial stretching, is used to test the model. With the introduction of a revised strain measure which includes a Mooney-Rivlin term, all of these motions can be well described by the damage function described in previous papers. For reversing step strains, larger amplitude oscillatory shearing and recoil reasonable predictions have been found. The numerical methods used are discussed and we give some examples.
Stability of cylindrical plasma in the Bessel function model
International Nuclear Information System (INIS)
Yamagishi, T.; Gimblett, C.G.
1988-01-01
The stability of free boundary ideal and tearing modes in a cylindrical plasma is studied by examining the discontinuity (Δ') of the helical flux function given by the force free Bessel function model at the singular surface. The m = O and m = 1 free boundary tearing modes become strongly unstable when the singular surface is just inside the plasma boundary for a wide range of longitudinal wave numbers. (author)
Four point functions in the SL(2,R) WZW model
Energy Technology Data Exchange (ETDEWEB)
Minces, Pablo [Instituto de Astronomia y Fisica del Espacio (IAFE), C.C. 67 Suc. 28, 1428 Buenos Aires (Argentina)]. E-mail: minces@iafe.uba.ar; Nunez, Carmen [Instituto de Astronomia y Fisica del Espacio (IAFE), C.C. 67 Suc. 28, 1428 Buenos Aires (Argentina) and Physics Department, University of Buenos Aires, Ciudad Universitaria, Pab. I, 1428 Buenos Aires (Argentina)]. E-mail: carmen@iafe.uba.ar
2007-04-19
We consider winding conserving four point functions in the SL(2,R) WZW model for states in arbitrary spectral flow sectors. We compute the leading order contribution to the expansion of the amplitudes in powers of the cross ratio of the four points on the worldsheet, both in the m- and x-basis, with at least one state in the spectral flow image of the highest weight discrete representation. We also perform certain consistency check on the winding conserving three point functions.
Four point functions in the SL(2,R) WZW model
International Nuclear Information System (INIS)
Minces, Pablo; Nunez, Carmen
2007-01-01
We consider winding conserving four point functions in the SL(2,R) WZW model for states in arbitrary spectral flow sectors. We compute the leading order contribution to the expansion of the amplitudes in powers of the cross ratio of the four points on the worldsheet, both in the m- and x-basis, with at least one state in the spectral flow image of the highest weight discrete representation. We also perform certain consistency check on the winding conserving three point functions
Applying Functional Modeling for Accident Management of Nuclear Power Plant
Energy Technology Data Exchange (ETDEWEB)
Lind, Morten; Zhang Xinxin [Harbin Engineering University, Harbin (China)
2014-08-15
The paper investigate applications of functional modeling for accident management in complex industrial plant with special reference to nuclear power production. Main applications for information sharing among decision makers and decision support are identified. An overview of Multilevel Flow Modeling is given and a detailed presentation of the foundational means-end concepts is presented and the conditions for proper use in modelling accidents are identified. It is shown that Multilevel Flow Modeling can be used for modelling and reasoning about design basis accidents. Its possible role for information sharing and decision support in accidents beyond design basis is also indicated. A modelling example demonstrating the application of Multilevel Flow Modelling and reasoning for a PWR LOCA is presented.
Using special functions to model the propagation of airborne diseases
Bolaños, Daniela
2014-06-01
Some special functions of the mathematical physics are using to obtain a mathematical model of the propagation of airborne diseases. In particular we study the propagation of tuberculosis in closed rooms and we model the propagation using the error function and the Bessel function. In the model, infected individual emit pathogens to the environment and this infect others individuals who absorb it. The evolution in time of the concentration of pathogens in the environment is computed in terms of error functions. The evolution in time of the number of susceptible individuals is expressed by a differential equation that contains the error function and it is solved numerically for different parametric simulations. The evolution in time of the number of infected individuals is plotted for each numerical simulation. On the other hand, the spatial distribution of the pathogen around the source of infection is represented by the Bessel function K0. The spatial and temporal distribution of the number of infected individuals is computed and plotted for some numerical simulations. All computations were made using software Computer algebra, specifically Maple. It is expected that the analytical results that we obtained allow the design of treatment rooms and ventilation systems that reduce the risk of spread of tuberculosis.
Enabling Cross-Discipline Collaboration Via a Functional Data Model
Lindholm, D. M.; Wilson, A.; Baltzer, T.
2016-12-01
Many research disciplines have very specialized data models that are used to express the detailed semantics that are meaningful to that community and easily utilized by their data analysis tools. While invaluable to members of that community, such expressive data structures and metadata are of little value to potential collaborators from other scientific disciplines. Many data interoperability efforts focus on the difficult task of computationally mapping concepts from one domain to another to facilitate discovery and use of data. Although these efforts are important and promising, we have found that a great deal of discovery and dataset understanding still happens at the level of less formal, personal communication. However, a significant barrier to inter-disciplinary data sharing that remains is one of data access.Scientists and data analysts continue to spend inordinate amounts of time simply trying to get data into their analysis tools. Providing data in a standard file format is often not sufficient since data can be structured in many ways. Adhering to more explicit community standards for data structure and metadata does little to help those in other communities.The Functional Data Model specializes the Relational Data Model (used by many database systems)by defining relations as functions between independent (domain) and dependent (codomain) variables. Given that arrays of data in many scientific data formats generally represent functionally related parameters (e.g. temperature as a function of space and time), the Functional Data Model is quite relevant for these datasets as well. The LaTiS software framework implements the Functional Data Model and provides a mechanism to expose an existing data source as a LaTiS dataset. LaTiS datasets can be manipulated using a Functional Algebra and output in any number of formats.LASP has successfully used the Functional Data Model and its implementation in the LaTiS software framework to bridge the gap between
Optimal hemodynamic response model for functional near-infrared spectroscopy
Directory of Open Access Journals (Sweden)
Muhammad Ahmad Kamran
2015-06-01
Full Text Available Functional near-infrared spectroscopy (fNIRS is an emerging non-invasive brain imaging technique and measures brain activities by means of near-infrared light of 650-950 nm wavelengths. The cortical hemodynamic response (HR differs in attributes at different brain regions and on repetition of trials, even if the experimental paradigm is kept exactly the same. Therefore, an HR model that can estimate such variations in the response is the objective of this research. The canonical hemodynamic response function (cHRF is modeled by using two Gamma functions with six unknown parameters. The HRF model is supposed to be linear combination of HRF, baseline and physiological noises (amplitudes and frequencies of physiological noises are supposed to be unknown. An objective function is developed as a square of the residuals with constraints on twelve free parameters. The formulated problem is solved by using an iterative optimization algorithm to estimate the unknown parameters in the model. Inter-subject variations in HRF and physiological noises have been estimated for better cortical functional maps. The accuracy of the algorithm has been verified using ten real and fifteen simulated data sets. Ten healthy subjects participated in the experiment and their HRF for finger-tapping tasks have been estimated and analyzed. The statistical significance of the estimated activity strength parameters has been verified by employing statistical analysis, i.e., (t-value >tcritical and p-value < 0.05.
Using Lambert W function and error function to model phase change on microfluidics
Bermudez Garcia, Anderson
2014-05-01
Solidification and melting modeling on microfluidics are solved using Lambert W's function and error's functions. Models are formulated using the heat's diffusion equation. The generic posed case is the melting of a slab with time dependent surface temperature, having a micro or nano-fluid liquid phase. At the beginning the solid slab is at melting temperature. A slab's face is put and maintained at temperature greater than the melting limit and varying in time. Lambert W function and error function are applied via Maple to obtain the analytic solution evolution of the front of microfluidic-solid interface, it is analytically computed and slab's corresponding melting time is determined. It is expected to have analytical results to be useful for food engineering, cooking engineering, pharmaceutical engineering, nano-engineering and bio-medical engineering.
Functional dynamic factor models with application to yield curve forecasting
Hays, Spencer
2012-09-01
Accurate forecasting of zero coupon bond yields for a continuum of maturities is paramount to bond portfolio management and derivative security pricing. Yet a universal model for yield curve forecasting has been elusive, and prior attempts often resulted in a trade-off between goodness of fit and consistency with economic theory. To address this, herein we propose a novel formulation which connects the dynamic factor model (DFM) framework with concepts from functional data analysis: a DFM with functional factor loading curves. This results in a model capable of forecasting functional time series. Further, in the yield curve context we show that the model retains economic interpretation. Model estimation is achieved through an expectation- maximization algorithm, where the time series parameters and factor loading curves are simultaneously estimated in a single step. Efficient computing is implemented and a data-driven smoothing parameter is nicely incorporated. We show that our model performs very well on forecasting actual yield data compared with existing approaches, especially in regard to profit-based assessment for an innovative trading exercise. We further illustrate the viability of our model to applications outside of yield forecasting.
Collapse of the wave function models, ontology, origin, and implications
2018-01-01
This is the first single volume about the collapse theories of quantum mechanics, which is becoming a very active field of research in both physics and philosophy. In standard quantum mechanics, it is postulated that when the wave function of a quantum system is measured, it no longer follows the Schrödinger equation, but instantaneously and randomly collapses to one of the wave functions that correspond to definite measurement results. However, why and how a definite measurement result appears is unknown. A promising solution to this problem are collapse theories in which the collapse of the wave function is spontaneous and dynamical. Chapters written by distinguished physicists and philosophers of physics discuss the origin and implications of wave-function collapse, the controversies around collapse models and their ontologies, and new arguments for the reality of wave function collapse. This is an invaluable resource for students and researchers interested in the philosophy of physics and foundations of ...
DEFINE: A Service-Oriented Dynamically Enabling Function Model
Directory of Open Access Journals (Sweden)
Tan Wei-Yi
2017-01-01
In this paper, we introduce an innovative Dynamically Enable Function In Network Equipment (DEFINE to allow tenant get the network service quickly. First, DEFINE decouples an application into different functional components, and connects these function components in a reconfigurable method. Second, DEFINE provides a programmable interface to the third party, who can develop their own processing modules according to their own needs. To verify the effectiveness of this model, we set up an evaluating network with a FPGA-based OpenFlow switch prototype, and deployed several applications on it. Our results show that DEFINE has excellent flexibility and performance.
Green function simulation of Hamiltonian lattice models with stochastic reconfiguration
International Nuclear Information System (INIS)
Beccaria, M.
2000-01-01
We apply a recently proposed Green function Monte Carlo procedure to the study of Hamiltonian lattice gauge theories. This class of algorithms computes quantum vacuum expectation values by averaging over a set of suitable weighted random walkers. By means of a procedure called stochastic reconfiguration the long standing problem of keeping fixed the walker population without a priori knowledge of the ground state is completely solved. In the U(1) 2 model, which we choose as our theoretical laboratory, we evaluate the mean plaquette and the vacuum energy per plaquette. We find good agreement with previous works using model-dependent guiding functions for the random walkers. (orig.)
Predicting Cumulative Incidence Probability by Direct Binomial Regression
DEFF Research Database (Denmark)
Scheike, Thomas H.; Zhang, Mei-Jie
Binomial modelling; cumulative incidence probability; cause-specific hazards; subdistribution hazard......Binomial modelling; cumulative incidence probability; cause-specific hazards; subdistribution hazard...
Hypnosis as a model of functional neurologic disorders.
Deeley, Q
2016-01-01
In the 19th century it was recognized that neurologic symptoms could be caused by "morbid ideation" as well as organic lesions. The subsequent observation that hysteric (now called "functional") symptoms could be produced and removed by hypnotic suggestion led Charcot to hypothesize that suggestion mediated the effects of ideas on hysteric symptoms through as yet unknown effects on brain activity. The advent of neuroimaging 100 years later revealed strikingly similar neural correlates in experiments matching functional symptoms with clinical analogs created by suggestion. Integrative models of suggested and functional symptoms regard these alterations in brain function as the endpoint of a broader set of changes in information processing due to suggestion. These accounts consider that suggestions alter experience by mobilizing representations from memory systems, and altering causal attributions, during preconscious processing which alters the content of what is provided to our highly edited subjective version of the world. Hypnosis as a model for functional symptoms draws attention to how radical alterations in experience and behavior can conform to the content of mental representations through effects on cognition and brain function. Experimental study of functional symptoms and their suggested counterparts in hypnosis reveals the distinct and shared processes through which this can occur. © 2016 Elsevier B.V. All rights reserved.
Bethea, Cynthia L; Kim, Aaron; Cameron, Judy L
2012-01-01
A body of knowledge implicates an increase in output from the locus ceruleus (LC) during stress. We questioned the innervation and function of the LC in our macaque model of Functional Hypothalamic Amenorrhea, also known as Stress-Induced Amenorrhea. Cohorts of macaques were initially characterized as highly stress resilient (HSR) or stress-sensitive (SS) based upon the presence or absence of ovulation during a protocol involving 2 menstrual cycles with psychosocial and metabolic stress. Afte...
Descriptions and models of safety functions - a prestudy
International Nuclear Information System (INIS)
Harms-Ringdahl, L.
1999-09-01
A study has been made with the focus on different theories and applications concerning 'safety functions' and 'barriers'. In this report, a safety function is defined as a technical or organisational function with the aim to reduce probability and/or consequences associated with a hazard. The study contains a limited review of practice and theories related to safety, with a focus on applications from nuclear and industrial safety. The study is based on a literature review and interviews. A summary has been made of definitions and terminology, which shows a large variation. E.g. 'barrier' can have a precise physical and technical meaning, or it can include human, technical and organisational elements. Only a few theoretical models describing safety functions have been found. One section of the report summarises problems related to safety issues and procedures. They concern errors in procedure design and user compliance. A proposal for describing and structuring safety functions has been made. Dimensions in a description could be degree of abstraction, systems level, the different parts of the function, etc. A model for safety functions has been proposed, which includes the division of a safety function in a number connected 'safety function elements'. One conclusion is that there is a potential for improving theories and tools for safety work and procedures. Safety function could be a useful concept in such a development, and advantages and disadvantages with this is discussed. If further work should be done, it is recommended that this is made as a combination of theoretical analysis and case studies
Structure, function, and behaviour of computational models in systems biology.
Knüpfer, Christian; Beckstein, Clemens; Dittrich, Peter; Le Novère, Nicolas
2013-05-31
Systems Biology develops computational models in order to understand biological phenomena. The increasing number and complexity of such "bio-models" necessitate computer support for the overall modelling task. Computer-aided modelling has to be based on a formal semantic description of bio-models. But, even if computational bio-models themselves are represented precisely in terms of mathematical expressions their full meaning is not yet formally specified and only described in natural language. We present a conceptual framework - the meaning facets - which can be used to rigorously specify the semantics of bio-models. A bio-model has a dual interpretation: On the one hand it is a mathematical expression which can be used in computational simulations (intrinsic meaning). On the other hand the model is related to the biological reality (extrinsic meaning). We show that in both cases this interpretation should be performed from three perspectives: the meaning of the model's components (structure), the meaning of the model's intended use (function), and the meaning of the model's dynamics (behaviour). In order to demonstrate the strengths of the meaning facets framework we apply it to two semantically related models of the cell cycle. Thereby, we make use of existing approaches for computer representation of bio-models as much as possible and sketch the missing pieces. The meaning facets framework provides a systematic in-depth approach to the semantics of bio-models. It can serve two important purposes: First, it specifies and structures the information which biologists have to take into account if they build, use and exchange models. Secondly, because it can be formalised, the framework is a solid foundation for any sort of computer support in bio-modelling. The proposed conceptual framework establishes a new methodology for modelling in Systems Biology and constitutes a basis for computer-aided collaborative research.
Functional results-oriented healthcare leadership: a novel leadership model.
Al-Touby, Salem Said
2012-03-01
This article modifies the traditional functional leadership model to accommodate contemporary needs in healthcare leadership based on two findings. First, the article argues that it is important that the ideal healthcare leadership emphasizes the outcomes of the patient care more than processes and structures used to deliver such care; and secondly, that the leadership must strive to attain effectiveness of their care provision and not merely targeting the attractive option of efficient operations. Based on these premises, the paper reviews the traditional Functional Leadership Model and the three elements that define the type of leadership an organization has namely, the tasks, the individuals, and the team. The article argues that concentrating on any one of these elements is not ideal and proposes adding a new element to the model to construct a novel Functional Result-Oriented healthcare leadership model. The recommended Functional-Results Oriented leadership model embosses the results element on top of the other three elements so that every effort on healthcare leadership is directed towards attaining excellent patient outcomes.
Zhang, Liping; Zheng, Yanling; Wang, Kai; Zhang, Xueliang; Zheng, Yujian
2014-06-01
In this paper, by using a particle swarm optimization algorithm to solve the optimal parameter estimation problem, an improved Nash nonlinear grey Bernoulli model termed PSO-NNGBM(1,1) is proposed. To test the forecasting performance, the optimized model is applied for forecasting the incidence of hepatitis B in Xinjiang, China. Four models, traditional GM(1,1), grey Verhulst model (GVM), original nonlinear grey Bernoulli model (NGBM(1,1)) and Holt-Winters exponential smoothing method, are also established for comparison with the proposed model under the criteria of mean absolute percentage error and root mean square percent error. The prediction results show that the optimized NNGBM(1,1) model is more accurate and performs better than the traditional GM(1,1), GVM, NGBM(1,1) and Holt-Winters exponential smoothing method. Copyright © 2014. Published by Elsevier Ltd.
Cohesive fracture model for functionally graded fiber reinforced concrete
International Nuclear Information System (INIS)
Park, Kyoungsoo; Paulino, Glaucio H.; Roesler, Jeffery
2010-01-01
A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.
Regional differences in prediction models of lung function in Germany
Directory of Open Access Journals (Sweden)
Schäper Christoph
2010-04-01
Full Text Available Abstract Background Little is known about the influencing potential of specific characteristics on lung function in different populations. The aim of this analysis was to determine whether lung function determinants differ between subpopulations within Germany and whether prediction equations developed for one subpopulation are also adequate for another subpopulation. Methods Within three studies (KORA C, SHIP-I, ECRHS-I in different areas of Germany 4059 adults performed lung function tests. The available data consisted of forced expiratory volume in one second, forced vital capacity and peak expiratory flow rate. For each study multivariate regression models were developed to predict lung function and Bland-Altman plots were established to evaluate the agreement between predicted and measured values. Results The final regression equations for FEV1 and FVC showed adjusted r-square values between 0.65 and 0.75, and for PEF they were between 0.46 and 0.61. In all studies gender, age, height and pack-years were significant determinants, each with a similar effect size. Regarding other predictors there were some, although not statistically significant, differences between the studies. Bland-Altman plots indicated that the regression models for each individual study adequately predict medium (i.e. normal but not extremely high or low lung function values in the whole study population. Conclusions Simple models with gender, age and height explain a substantial part of lung function variance whereas further determinants add less than 5% to the total explained r-squared, at least for FEV1 and FVC. Thus, for different adult subpopulations of Germany one simple model for each lung function measures is still sufficient.
Lyapunov functions for a dengue disease transmission model
International Nuclear Information System (INIS)
Tewa, Jean Jules; Dimi, Jean Luc; Bowong, Samuel
2009-01-01
In this paper, we study a model for the dynamics of dengue fever when only one type of virus is present. For this model, Lyapunov functions are used to show that when the basic reproduction ratio is less than or equal to one, the disease-free equilibrium is globally asymptotically stable, and when it is greater than one there is an endemic equilibrium which is also globally asymptotically stable.
Lyapunov functions for a dengue disease transmission model
Energy Technology Data Exchange (ETDEWEB)
Tewa, Jean Jules [Department of Mathematics, Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde (Cameroon)], E-mail: tewa@univ-metz.fr; Dimi, Jean Luc [Department of Mathematics, Faculty of Science, University Marien Ngouabi, P.O. Box 69, Brazzaville (Congo, The Democratic Republic of the)], E-mail: jldimi@yahoo.fr; Bowong, Samuel [Department of Mathematics and Computer Science, Faculty of Science, University of Douala, P.O. Box 24157, Douala (Cameroon)], E-mail: samuelbowong@yahoo.fr
2009-01-30
In this paper, we study a model for the dynamics of dengue fever when only one type of virus is present. For this model, Lyapunov functions are used to show that when the basic reproduction ratio is less than or equal to one, the disease-free equilibrium is globally asymptotically stable, and when it is greater than one there is an endemic equilibrium which is also globally asymptotically stable.
Towards aspect-oriented functional--structural plant modelling.
Cieslak, Mikolaj; Seleznyova, Alla N; Prusinkiewicz, Przemyslaw; Hanan, Jim
2011-10-01
Functional-structural plant models (FSPMs) are used to integrate knowledge and test hypotheses of plant behaviour, and to aid in the development of decision support systems. A significant amount of effort is being put into providing a sound methodology for building them. Standard techniques, such as procedural or object-oriented programming, are not suited for clearly separating aspects of plant function that criss-cross between different components of plant structure, which makes it difficult to reuse and share their implementations. The aim of this paper is to present an aspect-oriented programming approach that helps to overcome this difficulty. The L-system-based plant modelling language L+C was used to develop an aspect-oriented approach to plant modelling based on multi-modules. Each element of the plant structure was represented by a sequence of L-system modules (rather than a single module), with each module representing an aspect of the element's function. Separate sets of productions were used for modelling each aspect, with context-sensitive rules facilitated by local lists of modules to consider/ignore. Aspect weaving or communication between aspects was made possible through the use of pseudo-L-systems, where the strict-predecessor of a production rule was specified as a multi-module. The new approach was used to integrate previously modelled aspects of carbon dynamics, apical dominance and biomechanics with a model of a developing kiwifruit shoot. These aspects were specified independently and their implementation was based on source code provided by the original authors without major changes. This new aspect-oriented approach to plant modelling is well suited for studying complex phenomena in plant science, because it can be used to integrate separate models of individual aspects of plant development and function, both previously constructed and new, into clearly organized, comprehensive FSPMs. In a future work, this approach could be further
Regulator Loss Functions and Hierarchical Modeling for Safety Decision Making.
Hatfield, Laura A; Baugh, Christine M; Azzone, Vanessa; Normand, Sharon-Lise T
2017-07-01
Regulators must act to protect the public when evidence indicates safety problems with medical devices. This requires complex tradeoffs among risks and benefits, which conventional safety surveillance methods do not incorporate. To combine explicit regulator loss functions with statistical evidence on medical device safety signals to improve decision making. In the Hospital Cost and Utilization Project National Inpatient Sample, we select pediatric inpatient admissions and identify adverse medical device events (AMDEs). We fit hierarchical Bayesian models to the annual hospital-level AMDE rates, accounting for patient and hospital characteristics. These models produce expected AMDE rates (a safety target), against which we compare the observed rates in a test year to compute a safety signal. We specify a set of loss functions that quantify the costs and benefits of each action as a function of the safety signal. We integrate the loss functions over the posterior distribution of the safety signal to obtain the posterior (Bayes) risk; the preferred action has the smallest Bayes risk. Using simulation and an analysis of AMDE data, we compare our minimum-risk decisions to a conventional Z score approach for classifying safety signals. The 2 rules produced different actions for nearly half of hospitals (45%). In the simulation, decisions that minimize Bayes risk outperform Z score-based decisions, even when the loss functions or hierarchical models are misspecified. Our method is sensitive to the choice of loss functions; eliciting quantitative inputs to the loss functions from regulators is challenging. A decision-theoretic approach to acting on safety signals is potentially promising but requires careful specification of loss functions in consultation with subject matter experts.
Bifurcations in a discrete time model composed of Beverton-Holt function and Ricker function.
Shang, Jin; Li, Bingtuan; Barnard, Michael R
2015-05-01
We provide rigorous analysis for a discrete-time model composed of the Ricker function and Beverton-Holt function. This model was proposed by Lewis and Li [Bull. Math. Biol. 74 (2012) 2383-2402] in the study of a population in which reproduction occurs at a discrete instant of time whereas death and competition take place continuously during the season. We show analytically that there exists a period-doubling bifurcation curve in the model. The bifurcation curve divides the parameter space into the region of stability and the region of instability. We demonstrate through numerical bifurcation diagrams that the regions of periodic cycles are intermixed with the regions of chaos. We also study the global stability of the model. Copyright © 2015 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Sumida, S [U-shin Ltd., Tokyo (Japan); Nagamatsu, M; Maruyama, K [Hokkaido Institute of Technology, Sapporo (Japan); Hiramatsu, S [Mazda Motor Corp., Hiroshima (Japan)
1997-10-01
A new approach on modeling is put forward in order to compose the virtual prototype which is indispensable for fully computer integrated concurrent development of automobile product. A basic concept of the hierarchical functional model is proposed as the concrete form of this new modeling technology. This model is used mainly for explaining and simulating functions and efficiencies of both the parts and the total product of automobile. All engineers who engage themselves in design and development of automobile can collaborate with one another using this model. Some application examples are shown, and usefulness of this model is demonstrated. 5 refs., 5 figs.
Directory of Open Access Journals (Sweden)
Solomencevs Artūrs
2016-05-01
Full Text Available The approach called “Topological Functioning Model for Software Engineering” (TFM4SE applies the Topological Functioning Model (TFM for modelling the business system in the context of Model Driven Architecture. TFM is a mathematically formal computation independent model (CIM. TFM4SE is compared to an approach that uses BPMN as a CIM. The comparison focuses on CIM modelling and on transformation to UML Sequence diagram on the platform independent (PIM level. The results show the advantages and drawbacks the formalism of TFM brings into the development.
The functional neuroanatomy of bipolar disorder: a consensus model
Strakowski, Stephen M; Adler, Caleb M; Almeida, Jorge; Altshuler, Lori L; Blumberg, Hilary P; Chang, Kiki D; DelBello, Melissa P; Frangou, Sophia; McIntosh, Andrew; Phillips, Mary L; Sussman, Jessika E; Townsend, Jennifer D
2013-01-01
Objectives Functional neuroimaging methods have proliferated in recent years, such that functional magnetic resonance imaging, in particular, is now widely used to study bipolar disorder. However, discrepant findings are common. A workgroup was organized by the Department of Psychiatry, University of Cincinnati (Cincinnati, OH, USA) to develop a consensus functional neuroanatomic model of bipolar I disorder based upon the participants’ work as well as that of others. Methods Representatives from several leading bipolar disorder neuroimaging groups were organized to present an overview of their areas of expertise as well as focused reviews of existing data. The workgroup then developed a consensus model of the functional neuroanatomy of bipolar disorder based upon these data. Results Among the participants, a general consensus emerged that bipolar I disorder arises from abnormalities in the structure and function of key emotional control networks in the human brain. Namely, disruption in early development (e.g., white matter connectivity, prefrontal pruning) within brain networks that modulate emotional behavior leads to decreased connectivity among ventral prefrontal networks and limbic brain regions, especially amygdala. This developmental failure to establish healthy ventral prefrontal–limbic modulation underlies the onset of mania and ultimately, with progressive changes throughout these networks over time and with affective episodes, a bipolar course of illness. Conclusions This model provides a potential substrate to guide future investigations and areas needing additional focus are identified. PMID:22631617
Mass corrections to Green functions in instanton vacuum model
International Nuclear Information System (INIS)
Esaibegyan, S.V.; Tamaryan, S.N.
1987-01-01
The first nonvanishing mass corrections to the effective Green functions are calculated in the model of instanton-based vacuum consisting of a superposition of instanton-antiinstanton fluctuations. The meson current correlators are calculated with account of these corrections; the mass spectrum of pseudoscalar octet as well as the value of the kaon axial constant are found. 7 refs
How to Maximize the Likelihood Function for a DSGE Model
DEFF Research Database (Denmark)
Andreasen, Martin Møller
This paper extends two optimization routines to deal with objective functions for DSGE models. The optimization routines are i) a version of Simulated Annealing developed by Corana, Marchesi & Ridella (1987), and ii) the evolutionary algorithm CMA-ES developed by Hansen, Müller & Koumoutsakos (2003...
A review of function modeling : Approaches and applications
Erden, M.S.; Komoto, H.; Van Beek, T.J.; D'Amelio, V.; Echavarria, E.; Tomiyama, T.
2008-01-01
This work is aimed at establishing a common frame and understanding of function modeling (FM) for our ongoing research activities. A comparative review of the literature is performed to grasp the various FM approaches with their commonalities and differences. The relations of FM with the research
Gene Discovery and Functional Analyses in the Model Plant Arabidopsis
DEFF Research Database (Denmark)
Feng, Cai-ping; Mundy, J.
2006-01-01
The present mini-review describes newer methods and strategies, including transposon and T-DNA insertions, TILLING, Deleteagene, and RNA interference, to functionally analyze genes of interest in the model plant Arabidopsis. The relative advantages and disadvantages of the systems are also discus...
From dynamics to structure and function of model biomolecular systems
Fontaine-Vive-Curtaz, F.
2007-01-01
The purpose of this thesis was to extend recent works on structure and dynamics of hydrogen bonded crystals to model biomolecular systems and biological processes. The tools that we have used are neutron scattering (NS) and density functional theory (DFT) and force field (FF) based simulation
Density-correlation functions in Calogero-Sutherland models
International Nuclear Information System (INIS)
Minahan, J.A.; Polychronakos, A.P.
1994-01-01
Using arguments from two-dimensional Yang-Mills theory and the collective coordinate formulation of the Calogero-Sutherland model, we conjecture the dynamical density-correlation function for coupling l and 1/l, where l is an integer. We present overwhelming evidence that the conjecture is indeed correct
Density correlation functions in Calogero-Sutherland models
Minahan, Joseph A.; Joseph A Minahan; Alexios P Polychronakos
1994-01-01
Using arguments from two dimensional Yang-Mills theory and the collective coordinate formulation of the Calogero-Sutherland model, we conjecture the dynamical density correlation function for coupling l and 1/l, where l is an integer. We present overwhelming evidence that the conjecture is indeed correct.
A Multi-Level Model of Moral Functioning Revisited
Reed, Don Collins
2009-01-01
The model of moral functioning scaffolded in the 2008 "JME" Special Issue is here revisited in response to three papers criticising that volume. As guest editor of that Special Issue I have formulated the main body of this response, concerning the dynamic systems approach to moral development, the problem of moral relativism and the role of…
Rosales, Juan Carlos; Yang, Hyun Mo; Avila Blas, Orlando José
2014-01-01
American tegumentary leishmaniasis (ATL) is a disease transmitted to humans by the female sandflies of the genus Lutzomyia. Several factors are involved in the disease transmission cycle. In this work only rainfall and deforestation were considered to assess the variability in the incidence of ATL. In order to reach this goal, monthly recorded data of the incidence of ATL in Orán, Salta, Argentina, were used, in the period 1985-2007. The square root of the relative incidence of ATL and the corresponding variance were formulated as time series, and these data were smoothed by moving averages of 12 and 24 months, respectively. The same procedure was applied to the rainfall data. Typical months, which are April, August, and December, were found and allowed us to describe the dynamical behavior of ATL outbreaks. These results were tested at 95% confidence level. We concluded that the variability of rainfall would not be enough to justify the epidemic outbreaks of ATL in the period 1997-2000, but it consistently explains the situation observed in the years 2002 and 2004. Deforestation activities occurred in this region could explain epidemic peaks observed in both years and also during the entire time of observation except in 2005-2007.
Directory of Open Access Journals (Sweden)
Juan Carlos Rosales
2014-01-01
Full Text Available American tegumentary leishmaniasis (ATL is a disease transmitted to humans by the female sandflies of the genus Lutzomyia. Several factors are involved in the disease transmission cycle. In this work only rainfall and deforestation were considered to assess the variability in the incidence of ATL. In order to reach this goal, monthly recorded data of the incidence of ATL in Orán, Salta, Argentina, were used, in the period 1985–2007. The square root of the relative incidence of ATL and the corresponding variance were formulated as time series, and these data were smoothed by moving averages of 12 and 24 months, respectively. The same procedure was applied to the rainfall data. Typical months, which are April, August, and December, were found and allowed us to describe the dynamical behavior of ATL outbreaks. These results were tested at 95% confidence level. We concluded that the variability of rainfall would not be enough to justify the epidemic outbreaks of ATL in the period 1997–2000, but it consistently explains the situation observed in the years 2002 and 2004. Deforestation activities occurred in this region could explain epidemic peaks observed in both years and also during the entire time of observation except in 2005–2007.
Describing a Strongly Correlated Model System with Density Functional Theory.
Kong, Jing; Proynov, Emil; Yu, Jianguo; Pachter, Ruth
2017-07-06
The linear chain of hydrogen atoms, a basic prototype for the transition from a metal to Mott insulator, is studied with a recent density functional theory model functional for nondynamic and strong correlation. The computed cohesive energy curve for the transition agrees well with accurate literature results. The variation of the electronic structure in this transition is characterized with a density functional descriptor that yields the atomic population of effectively localized electrons. These new methods are also applied to the study of the Peierls dimerization of the stretched even-spaced Mott insulator to a chain of H 2 molecules, a different insulator. The transitions among the two insulating states and the metallic state of the hydrogen chain system are depicted in a semiquantitative phase diagram. Overall, we demonstrate the capability of studying strongly correlated materials with a mean-field model at the fundamental level, in contrast to the general pessimistic view on such a feasibility.
Development on electromagnetic impedance function modeling and its estimation
Energy Technology Data Exchange (ETDEWEB)
Sutarno, D., E-mail: Sutarno@fi.itb.ac.id [Earth Physics and Complex System Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (Indonesia)
2015-09-30
Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition
Universality of correlation functions in random matrix models of QCD
International Nuclear Information System (INIS)
Jackson, A.D.; Sener, M.K.; Verbaarschot, J.J.M.
1997-01-01
We demonstrate the universality of the spectral correlation functions of a QCD inspired random matrix model that consists of a random part having the chiral structure of the QCD Dirac operator and a deterministic part which describes a schematic temperature dependence. We calculate the correlation functions analytically using the technique of Itzykson-Zuber integrals for arbitrary complex supermatrices. An alternative exact calculation for arbitrary matrix size is given for the special case of zero temperature, and we reproduce the well-known Laguerre kernel. At finite temperature, the microscopic limit of the correlation functions are calculated in the saddle-point approximation. The main result of this paper is that the microscopic universality of correlation functions is maintained even though unitary invariance is broken by the addition of a deterministic matrix to the ensemble. (orig.)
Bessel functions in mass action modeling of memories and remembrances
Energy Technology Data Exchange (ETDEWEB)
Freeman, Walter J. [Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3206 (United States); Capolupo, Antonio [Dipartimento di Fisica, E.R. Caianiello Universitá di Salerno, and INFN Gruppo collegato di Salerno, Fisciano 84084 (Italy); Kozma, Robert [Department of Mathematics, Memphis University, Memphis, TN 38152 (United States); Olivares del Campo, Andrés [The Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom); Vitiello, Giuseppe, E-mail: vitiello@sa.infn.it [Dipartimento di Fisica, E.R. Caianiello Universitá di Salerno, and INFN Gruppo collegato di Salerno, Fisciano 84084 (Italy)
2015-10-02
Data from experimental observations of a class of neurological processes (Freeman K-sets) present functional distribution reproducing Bessel function behavior. We model such processes with couples of damped/amplified oscillators which provide time dependent representation of Bessel equation. The root loci of poles and zeros conform to solutions of K-sets. Some light is shed on the problem of filling the gap between the cellular level dynamics and the brain functional activity. Breakdown of time-reversal symmetry is related with the cortex thermodynamic features. This provides a possible mechanism to deduce lifetime of recorded memory. - Highlights: • We consider data from observations of impulse responses of cortex to electric shocks. • These data are fitted by Bessel functions which may be represented by couples of damped/amplified oscillators. • We study the data by using couples of damped/amplified oscillators. • We discuss lifetime and other properties of the considered brain processes.
Optimal hemodynamic response model for functional near-infrared spectroscopy.
Kamran, Muhammad A; Jeong, Myung Yung; Mannan, Malik M N
2015-01-01
Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive brain imaging technique and measures brain activities by means of near-infrared light of 650-950 nm wavelengths. The cortical hemodynamic response (HR) differs in attributes at different brain regions and on repetition of trials, even if the experimental paradigm is kept exactly the same. Therefore, an HR model that can estimate such variations in the response is the objective of this research. The canonical hemodynamic response function (cHRF) is modeled by two Gamma functions with six unknown parameters (four of them to model the shape and other two to scale and baseline respectively). The HRF model is supposed to be a linear combination of HRF, baseline, and physiological noises (amplitudes and frequencies of physiological noises are supposed to be unknown). An objective function is developed as a square of the residuals with constraints on 12 free parameters. The formulated problem is solved by using an iterative optimization algorithm to estimate the unknown parameters in the model. Inter-subject variations in HRF and physiological noises have been estimated for better cortical functional maps. The accuracy of the algorithm has been verified using 10 real and 15 simulated data sets. Ten healthy subjects participated in the experiment and their HRF for finger-tapping tasks have been estimated and analyzed. The statistical significance of the estimated activity strength parameters has been verified by employing statistical analysis (i.e., t-value > t critical and p-value < 0.05).
Plant functional modelling as a basis for assessing the impact of management on plant safety
International Nuclear Information System (INIS)
Rasmussen, Birgitte; Petersen, Kurt E.
1999-01-01
A major objective of the present work is to provide means for representing a chemical process plant as a socio-technical system, so as to allow hazard identification at a high level in order to identify major targets for safety development. The main phases of the methodology are: (1) preparation of a plant functional model where a set of plant functions describes coherently hardware, software, operations, work organization and other safety related aspects. The basic principle is that any aspect of the plant can be represented by an object based upon an Intent and associated with each Intent are Methods, by which the Intent is realized, and Constraints, which limit the Intent. (2) Plant level hazard identification based on keywords/checklists and the functional model. (3) Development of incident scenarios and selection of hazardous situation with different safety characteristics. (4) Evaluation of the impact of management on plant safety through interviews. (5) Identification of safety critical ways of action in the management system, i.e. identification of possible error- and violation-producing conditions
Production functions for climate policy modeling. An empirical analysis
International Nuclear Information System (INIS)
Van der Werf, Edwin
2008-01-01
Quantitative models for climate policy modeling differ in the production structure used and in the sizes of the elasticities of substitution. The empirical foundation for both is generally lacking. This paper estimates the parameters of 2-level CES production functions with capital, labour and energy as inputs, and is the first to systematically compare all nesting structures. Using industry-level data from 12 OECD countries, we find that the nesting structure where capital and labour are combined first, fits the data best, but for most countries and industries we cannot reject that all three inputs can be put into one single nest. These two nesting structures are used by most climate models. However, while several climate policy models use a Cobb-Douglas function for (part of the) production function, we reject elasticities equal to one, in favour of considerably smaller values. Finally we find evidence for factor-specific technological change. With lower elasticities and with factor-specific technological change, some climate policy models may find a bigger effect of endogenous technological change on mitigating the costs of climate policy. (author)
Rationalisation of distribution functions for models of nanoparticle magnetism
International Nuclear Information System (INIS)
El-Hilo, M.; Chantrell, R.W.
2012-01-01
A formalism is presented which reconciles the use of different distribution functions of particle diameter in analytical models of the magnetic properties of nanoparticle systems. For the lognormal distribution a transformation is derived which shows that a distribution of volume fraction transforms into a lognormal distribution of particle number albeit with a modified median diameter. This transformation resolves an apparent discrepancy reported in Tournus and Tamion [Journal of Magnetism and Magnetic Materials 323 (2011) 1118]. - Highlights: ► We resolve a problem resulting from the misunderstanding of the nature. ► The nature of dispersion functions in models of nanoparticle magnetism. ► The derived transformation between distributions will be of benefit in comparing models and experimental results.
Parton distribution functions with QED corrections in the valon model
Mottaghizadeh, Marzieh; Taghavi Shahri, Fatemeh; Eslami, Parvin
2017-10-01
The parton distribution functions (PDFs) with QED corrections are obtained by solving the QCD ⊗QED DGLAP evolution equations in the framework of the "valon" model at the next-to-leading-order QCD and the leading-order QED approximations. Our results for the PDFs with QED corrections in this phenomenological model are in good agreement with the newly related CT14QED global fits code [Phys. Rev. D 93, 114015 (2016), 10.1103/PhysRevD.93.114015] and APFEL (NNPDF2.3QED) program [Comput. Phys. Commun. 185, 1647 (2014), 10.1016/j.cpc.2014.03.007] in a wide range of x =[10-5,1 ] and Q2=[0.283 ,108] GeV2 . The model calculations agree rather well with those codes. In the latter, we proposed a new method for studying the symmetry breaking of the sea quark distribution functions inside the proton.
Modeling of nanoscale liquid mixture transport by density functional hydrodynamics
Dinariev, Oleg Yu.; Evseev, Nikolay V.
2017-06-01
Modeling of multiphase compositional hydrodynamics at nanoscale is performed by means of density functional hydrodynamics (DFH). DFH is the method based on density functional theory and continuum mechanics. This method has been developed by the authors over 20 years and used for modeling in various multiphase hydrodynamic applications. In this paper, DFH was further extended to encompass phenomena inherent in liquids at nanoscale. The new DFH extension is based on the introduction of external potentials for chemical components. These potentials are localized in the vicinity of solid surfaces and take account of the van der Waals forces. A set of numerical examples, including disjoining pressure, film precursors, anomalous rheology, liquid in contact with heterogeneous surface, capillary condensation, and forward and reverse osmosis, is presented to demonstrate modeling capabilities.
Functional Somatic Syndromes: Emerging Biomedical Models and Traditional Chinese Medicine
Directory of Open Access Journals (Sweden)
Steven Tan
2004-01-01
Full Text Available The so-called functional somatic syndromes comprise a group of disorders that are primarily symptom-based, multisystemic in presentation and probably involve alterations in mind-brain-body interactions. The emerging neurobiological models of allostasis/allostatic load and of the emotional motor system show striking similarities with concepts used by Traditional Chinese Medicine (TCM to understand the functional somatic disorders and their underlying pathogenesis. These models incorporate a macroscopic perspective, accounting for the toll of acute and chronic traumas, physical and emotional stressors and the complex interactions between the mind, brain and body. The convergence of these biomedical models with the ancient paradigm of TCM may provide a new insight into scientifically verifiable diagnostic and therapeutic approaches for these common disorders.
Eaton, Jeffrey W.; Johnson, Leigh F.; Salomon, Joshua A.; Bärnighausen, Till; Bendavid, Eran; Bershteyn, Anna; Bloom, David E.; Cambiano, Valentina; Fraser, Christophe; Hontelez, Jan A. C.; Humair, Salal; Klein, Daniel J.; Long, Elisa F.; Phillips, Andrew N.; Pretorius, Carel; Stover, John; Wenger, Edward A.; Williams, Brian G.; Hallett, Timothy B.
2012-01-01
Background Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART) on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART. Methods and Findings Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/µl and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y) reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results. Conclusions Mathematical models evaluating
Directory of Open Access Journals (Sweden)
Jeffrey W Eaton
Full Text Available Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART.Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/µl and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results.Mathematical models evaluating the impact of ART vary
Eaton, Jeffrey W; Johnson, Leigh F; Salomon, Joshua A; Bärnighausen, Till; Bendavid, Eran; Bershteyn, Anna; Bloom, David E; Cambiano, Valentina; Fraser, Christophe; Hontelez, Jan A C; Humair, Salal; Klein, Daniel J; Long, Elisa F; Phillips, Andrew N; Pretorius, Carel; Stover, John; Wenger, Edward A; Williams, Brian G; Hallett, Timothy B
2012-01-01
Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART) on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART. Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/µl and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y) reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results. Mathematical models evaluating the impact of ART vary substantially in
Future of Plant Functional Types in Terrestrial Biosphere Models
Wullschleger, S. D.; Euskirchen, E. S.; Iversen, C. M.; Rogers, A.; Serbin, S.
2015-12-01
Earth system models describe the physical, chemical, and biological processes that govern our global climate. While it is difficult to single out one component as being more important than another in these sophisticated models, terrestrial vegetation is a critical player in the biogeochemical and biophysical dynamics of the Earth system. There is much debate, however, as to how plant diversity and function should be represented in these models. Plant functional types (PFTs) have been adopted by modelers to represent broad groupings of plant species that share similar characteristics (e.g. growth form) and roles (e.g. photosynthetic pathway) in ecosystem function. In this review the PFT concept is traced from its origin in the early 1800s to its current use in regional and global dynamic vegetation models (DVMs). Special attention is given to the representation and parameterization of PFTs and to validation and benchmarking of predicted patterns of vegetation distribution in high-latitude ecosystems. These ecosystems are sensitive to changing climate and thus provide a useful test case for model-based simulations of past, current, and future distribution of vegetation. Models that incorporate the PFT concept predict many of the emerging patterns of vegetation change in tundra and boreal forests, given known processes of tree mortality, treeline migration, and shrub expansion. However, representation of above- and especially belowground traits for specific PFTs continues to be problematic. Potential solutions include developing trait databases and replacing fixed parameters for PFTs with formulations based on trait co-variance and empirical trait-environment relationships. Surprisingly, despite being important to land-atmosphere interactions of carbon, water, and energy, PFTs such as moss and lichen are largely absent from DVMs. Close collaboration among those involved in modelling with the disciplines of taxonomy, biogeography, ecology, and remote sensing will be
Functional Dual Adaptive Control with Recursive Gaussian Process Model
International Nuclear Information System (INIS)
Prüher, Jakub; Král, Ladislav
2015-01-01
The paper deals with dual adaptive control problem, where the functional uncertainties in the system description are modelled by a non-parametric Gaussian process regression model. Current approaches to adaptive control based on Gaussian process models are severely limited in their practical applicability, because the model is re-adjusted using all the currently available data, which keeps growing with every time step. We propose the use of recursive Gaussian process regression algorithm for significant reduction in computational requirements, thus bringing the Gaussian process-based adaptive controllers closer to their practical applicability. In this work, we design a bi-criterial dual controller based on recursive Gaussian process model for discrete-time stochastic dynamic systems given in an affine-in-control form. Using Monte Carlo simulations, we show that the proposed controller achieves comparable performance with the full Gaussian process-based controller in terms of control quality while keeping the computational demands bounded. (paper)
Development of an Upper Extremity Function Measurement Model.
Hong, Ickpyo; Simpson, Annie N; Li, Chih-Ying; Velozo, Craig A
This study demonstrated the development of a measurement model for gross upper-extremity function (GUE). The dependent variable was the Rasch calibration of the 27 ICF-GUE test items. The predictors were object weight, lifting distance from floor, carrying, and lifting. Multiple regression was used to investigate the contribution that each independent variable makes to the model with 203 outpatients. Object weight and lifting distance were the only statistically and clinically significant independent variables in the model, accounting for 83% of the variance (p model indicates that, with each one pound increase in object weight, item challenge increases by 0.16 (p measurement model for the ICF-GUE can be explained by object weight and distance lifted from the floor.
Functional requirements of a mathematical model of the heart.
Palladino, Joseph L; Noordergraaf, Abraham
2009-01-01
Functional descriptions of the heart, especially the left ventricle, are often based on the measured variables pressure and ventricular outflow, embodied as a time-varying elastance. The fundamental difficulty of describing the mechanical properties of the heart with a time-varying elastance function that is set a priori is described. As an alternative, a new functional model of the heart is presented, which characterizes the ventricle's contractile state with parameters, rather than variables. Each chamber is treated as a pressure generator that is time and volume dependent. The heart's complex dynamics develop from a single equation based on the formation and relaxation of crossbridge bonds. This equation permits the calculation of ventricular elastance via E(v) = partial differentialp(v)/ partial differentialV(v). This heart model is defined independently from load properties, and ventricular elastance is dynamic and reflects changing numbers of crossbridge bonds. In this paper, the functionality of this new heart model is presented via computed work loops that demonstrate the Frank-Starling mechanism and the effects of preload, the effects of afterload, inotropic changes, and varied heart rate, as well as the interdependence of these effects. Results suggest the origin of the equivalent of Hill's force-velocity relation in the ventricle.
Functional-derivative study of the Hubbard model. III. Fully renormalized Green's function
International Nuclear Information System (INIS)
Arai, T.; Cohen, M.H.
1980-01-01
The functional-derivative method of calculating the Green's function developed earlier for the Hubbard model is generalized and used to obtain a fully renormalized solution. Higher-order functional derivatives operating on the basic Green's functions, G and GAMMA, are all evaluated explicitly, thus making the solution applicable to the narrow-band region as well as the wide-band region. Correction terms Phi generated from functional derivatives of equal-time Green's functions of the type delta/sup n/ /deltaepsilon/sup n/, etc., with n > or = 2. It is found that the Phi's are, in fact, renormalization factors involved in the self-energy Σ and that the structure of the Phi's resembles that of Σ and contains the same renormalization factors Phi. The renormalization factors Phi are shown to satisfy a set of equations and can be evaluated self-consistently. In the presence of the Phi's, all difficulties found in the previous results (papers I and II) are removed, and the energy spectrum ω can now be evaluated for all occupations n. The Schwinger relation is the only basic relation used in generating this fully self-consistent Green's function, and the Baym-Kadanoff continuity condition is automatically satisfied
Correlation functions of the Ising model and the eight-vertex model
International Nuclear Information System (INIS)
Ko, L.F.
1986-01-01
Calculations for the two-point correlation functions in the scaling limit for two statistical models are presented. In Part I, the Ising model with a linear defect is studied for T T/sub c/. The transfer matrix method of Onsager and Kaufman is used. The energy-density correlation is given by functions related to the modified Bessel functions. The dispersion expansion for the spin-spin correlation functions are derived. The dominant behavior for large separations at T not equal to T/sub c/ is extracted. It is shown that these expansions lead to systems of Fredholm integral equations. In Part II, the electric correlation function of the eight-vertex model for T < T/sub c/ is studied. The eight vertex model decouples to two independent Ising models when the four spin coupling vanishes. To first order in the four-spin coupling, the electric correlation function is related to a three-point function of the Ising model. This relation is systematically investigated and the full dispersion expansion (to first order in four-spin coupling) is obtained. The results is a new kind of structure which, unlike those of many solvable models, is apparently not expressible in terms of linear integral equations
The Schroedinger functional for Gross-Neveu models
International Nuclear Information System (INIS)
Leder, B.
2007-01-01
Gross-Neveu type models with a finite number of fermion flavours are studied on a two-dimensional Euclidean space-time lattice. The models are asymptotically free and are invariant under a chiral symmetry. These similarities to QCD make them perfect benchmark systems for fermion actions used in large scale lattice QCD computations. The Schroedinger functional for the Gross-Neveu models is defined for both, Wilson and Ginsparg-Wilson fermions, and shown to be renormalisable in 1-loop lattice perturbation theory. In two dimensions four fermion interactions of the Gross-Neveu models have dimensionless coupling constants. The symmetry properties of the four fermion interaction terms and the relations among them are discussed. For Wilson fermions chiral symmetry is explicitly broken and additional terms must be included in the action. Chiral symmetry is restored up to cut-off effects by tuning the bare mass and one of the couplings. The critical mass and the symmetry restoring coupling are computed to second order in lattice perturbation theory. This result is used in the 1-loop computation of the renormalised couplings and the associated beta-functions. The renormalised couplings are defined in terms of suitable boundary-to-boundary correlation functions. In the computation the known first order coefficients of the beta-functions are reproduced. One of the couplings is found to have a vanishing betafunction. The calculation is repeated for the recently proposed Schroedinger functional with exact chiral symmetry, i.e. Ginsparg-Wilson fermions. The renormalisation pattern is found to be the same as in the Wilson case. Using the regularisation dependent finite part of the renormalised couplings, the ratio of the Lambda-parameters is computed. (orig.)
Campbell, Todd; Oh, Phil Seok; Maughn, Milo; Kiriazis, Nick; Zuwallack, Rebecca
2015-01-01
The current review examined modeling literature in top science education journals to better understand the pedagogical functions of modeling instruction reported over the last decade. Additionally, the review sought to understand the extent to which different modeling pedagogies were employed, the discursive acts that were identified as important,…
Directory of Open Access Journals (Sweden)
Gerhard Visser
2012-09-01
Full Text Available We investigated the application of a Minimum Message Length (MML modeling approach to identify the simplest model that would explain two target malaria incidence variables: incidence in the short term and on the average longer term, in two areas in Indonesia, based on a range of ecological variables including environmental and socio-economic ones. The approach is suitable for dealing with a variety of problems such as complexity and where there are missing values in the data. It can detect weak relations, is resistant to overfittingand can show the way in which many variables, working together, contribute to explaining malaria incidence. This last point is a major strength of the method as it allows many variables to be analysed. Data were obtained at household level by questionnaire for villages in West Timor and Central Java. Data were collected on 26 variables in nine categories: stratum (a village-level variable based on the API/AMI categories, ecology, occupation, preventative measures taken, health care facilities, the immediate environment, household characteristics, socio-economic status and perception of malaria cause. Several models were used and the simplest (best model, that is the one with the minimum message length was selected for each area. The results showed that consistent predictors of malaria included combinations of ecology (coastal, preventative (clean backyard and environment (mosquito breeding place, garden and rice cultivation. The models also showed that most of the other variables were not good predictors and this is discussed in the paper. We conclude that the method has potential for identifying simple predictors of malaria and that it could be used to focus malaria management on combinations of variables rather than relying on single ones that may not be consistently reliable.
Spin-density functional for exchange anisotropic Heisenberg model
International Nuclear Information System (INIS)
Prata, G.N.; Penteado, P.H.; Souza, F.C.; Libero, Valter L.
2009-01-01
Ground-state energies for antiferromagnetic Heisenberg models with exchange anisotropy are estimated by means of a local-spin approximation made in the context of the density functional theory. Correlation energy is obtained using the non-linear spin-wave theory for homogeneous systems from which the spin functional is built. Although applicable to chains of any size, the results are shown for small number of sites, to exhibit finite-size effects and allow comparison with exact-numerical data from direct diagonalization of small chains.
Medical Writing Competency Model - Section 1: Functions, Tasks, and Activities.
Clemow, David B; Wagner, Bertil; Marshallsay, Christopher; Benau, Dan; L'Heureux, Darryl; Brown, David H; Dasgupta, Devjani Ghosh; Girten, Eileen; Hubbard, Frank; Gawrylewski, Helle-Mai; Ebina, Hiroko; Stoltenborg, Janet; York, J P; Green, Kim; Wood, Linda Fossati; Toth, Lisa; Mihm, Michael; Katz, Nancy R; Vasconcelos, Nina-Maria; Sakiyama, Norihisa; Whitsell, Robin; Gopalakrishnan, Shobha; Bairnsfather, Susan; Wanderer, Tatyana; Schindler, Thomas M; Mikyas, Yeshi; Aoyama, Yumiko
2018-01-01
This article provides Section 1 of the 2017 Edition 2 Medical Writing Competency Model that describes the core work functions and associated tasks and activities related to professional medical writing within the life sciences industry. The functions in the Model are scientific communication strategy; document preparation, development, and finalization; document project management; document template, standard, format, and style development and maintenance; outsourcing, alliance partner, and client management; knowledge, skill, ability, and behavior development and sharing; and process improvement. The full Model also includes Section 2, which covers the knowledge, skills, abilities, and behaviors needed for medical writers to be effective in their roles; Section 2 is presented in a companion article. Regulatory, publication, and other scientific writing as well as management of writing activities are covered. The Model was developed to aid medical writers and managers within the life sciences industry regarding medical writing hiring, training, expectation and goal setting, performance evaluation, career development, retention, and role value sharing to cross-functional partners.
Analysis of a Heroin Epidemic Model with Saturated Treatment Function
Directory of Open Access Journals (Sweden)
Isaac Mwangi Wangari
2017-01-01
Full Text Available A mathematical model is developed that examines how heroin addiction spreads in society. The model is formulated to take into account the treatment of heroin users by incorporating a realistic functional form that “saturates” representing the limited availability of treatment. Bifurcation analysis reveals that the model has an intrinsic backward bifurcation whenever the saturation parameter is larger than a fixed threshold. We are particularly interested in studying the model’s global stability. In the absence of backward bifurcations, Lyapunov functions can often be found and used to prove global stability. However, in the presence of backward bifurcations, such Lyapunov functions may not exist or may be difficult to construct. We make use of the geometric approach to global stability to derive a condition that ensures that the system is globally asymptotically stable. Numerical simulations are also presented to give a more complete representation of the model dynamics. Sensitivity analysis performed by Latin hypercube sampling (LHS suggests that the effective contact rate in the population, the relapse rate of heroin users undergoing treatment, and the extent of saturation of heroin users are mechanisms fuelling heroin epidemic proliferation.
Lee, James S; Franc, Jeffrey M
2015-08-01
A high influx of patients during a mass-casualty incident (MCI) may disrupt patient flow in an already overcrowded emergency department (ED) that is functioning beyond its operating capacity. This pilot study examined the impact of a two-step ED triage model using Simple Triage and Rapid Treatment (START) for pre-triage, followed by triage with the Canadian Triage and Acuity Scale (CTAS), on patient flow during a MCI simulation exercise. Hypothesis/Problem It was hypothesized that there would be no difference in time intervals nor patient volumes at each patient-flow milestone. Physicians and nurses participated in a computer-based tabletop disaster simulation exercise. Physicians were randomized into the intervention group using START, then CTAS, or the control group using START alone. Patient-flow milestones including time intervals and patient volumes from ED arrival to triage, ED arrival to bed assignment, ED arrival to physician assessment, and ED arrival to disposition decision were compared. Triage accuracy was compared for secondary purposes. There were no significant differences in the time interval from ED arrival to triage (mean difference 108 seconds; 95% CI, -353 to 596 seconds; P=1.0), ED arrival to bed assignment (mean difference 362 seconds; 95% CI, -1,269 to 545 seconds; P=1.0), ED arrival to physician assessment (mean difference 31 seconds; 95% CI, -1,104 to 348 seconds; P=0.92), and ED arrival to disposition decision (mean difference 175 seconds; 95% CI, -1,650 to 1,300 seconds; P=1.0) between the two groups. There were no significant differences in the volume of patients to be triaged (32% vs 34%; 95% CI for the difference -16% to 21%; P=1.0), assigned a bed (16% vs 21%; 95% CI for the difference -11% to 20%; P=1.0), assessed by a physician (20% vs 22%; 95% CI for the difference -14% to 19%; P=1.0), and with a disposition decision (20% vs 9%; 95% CI for the difference -25% to 4%; P=.34) between the two groups. The accuracy of triage was similar
Functional Mixed Effects Model for Small Area Estimation.
Maiti, Tapabrata; Sinha, Samiran; Zhong, Ping-Shou
2016-09-01
Functional data analysis has become an important area of research due to its ability of handling high dimensional and complex data structures. However, the development is limited in the context of linear mixed effect models, and in particular, for small area estimation. The linear mixed effect models are the backbone of small area estimation. In this article, we consider area level data, and fit a varying coefficient linear mixed effect model where the varying coefficients are semi-parametrically modeled via B-splines. We propose a method of estimating the fixed effect parameters and consider prediction of random effects that can be implemented using a standard software. For measuring prediction uncertainties, we derive an analytical expression for the mean squared errors, and propose a method of estimating the mean squared errors. The procedure is illustrated via a real data example, and operating characteristics of the method are judged using finite sample simulation studies.
Model of bidirectional reflectance distribution function for metallic materials
International Nuclear Information System (INIS)
Wang Kai; Zhu Jing-Ping; Liu Hong; Hou Xun
2016-01-01
Based on the three-component assumption that the reflection is divided into specular reflection, directional diffuse reflection, and ideal diffuse reflection, a bidirectional reflectance distribution function (BRDF) model of metallic materials is presented. Compared with the two-component assumption that the reflection is composed of specular reflection and diffuse reflection, the three-component assumption divides the diffuse reflection into directional diffuse and ideal diffuse reflection. This model effectively resolves the problem that constant diffuse reflection leads to considerable error for metallic materials. Simulation and measurement results validate that this three-component BRDF model can improve the modeling accuracy significantly and describe the reflection properties in the hemisphere space precisely for the metallic materials. (paper)
Model of bidirectional reflectance distribution function for metallic materials
Wang, Kai; Zhu, Jing-Ping; Liu, Hong; Hou, Xun
2016-09-01
Based on the three-component assumption that the reflection is divided into specular reflection, directional diffuse reflection, and ideal diffuse reflection, a bidirectional reflectance distribution function (BRDF) model of metallic materials is presented. Compared with the two-component assumption that the reflection is composed of specular reflection and diffuse reflection, the three-component assumption divides the diffuse reflection into directional diffuse and ideal diffuse reflection. This model effectively resolves the problem that constant diffuse reflection leads to considerable error for metallic materials. Simulation and measurement results validate that this three-component BRDF model can improve the modeling accuracy significantly and describe the reflection properties in the hemisphere space precisely for the metallic materials.
A Tensor Statistical Model for Quantifying Dynamic Functional Connectivity.
Zhu, Yingying; Zhu, Xiaofeng; Kim, Minjeong; Yan, Jin; Wu, Guorong
2017-06-01
Functional connectivity (FC) has been widely investigated in many imaging-based neuroscience and clinical studies. Since functional Magnetic Resonance Image (MRI) signal is just an indirect reflection of brain activity, it is difficult to accurately quantify the FC strength only based on signal correlation. To address this limitation, we propose a learning-based tensor model to derive high sensitivity and specificity connectome biomarkers at the individual level from resting-state fMRI images. First, we propose a learning-based approach to estimate the intrinsic functional connectivity. In addition to the low level region-to-region signal correlation, latent module-to-module connection is also estimated and used to provide high level heuristics for measuring connectivity strength. Furthermore, sparsity constraint is employed to automatically remove the spurious connections, thus alleviating the issue of searching for optimal threshold. Second, we integrate our learning-based approach with the sliding-window technique to further reveal the dynamics of functional connectivity. Specifically, we stack the functional connectivity matrix within each sliding window and form a 3D tensor where the third dimension denotes for time. Then we obtain dynamic functional connectivity (dFC) for each individual subject by simultaneously estimating the within-sliding-window functional connectivity and characterizing the across-sliding-window temporal dynamics. Third, in order to enhance the robustness of the connectome patterns extracted from dFC, we extend the individual-based 3D tensors to a population-based 4D tensor (with the fourth dimension stands for the training subjects) and learn the statistics of connectome patterns via 4D tensor analysis. Since our 4D tensor model jointly (1) optimizes dFC for each training subject and (2) captures the principle connectome patterns, our statistical model gains more statistical power of representing new subject than current state
Simple model for low-frequency guitar function
DEFF Research Database (Denmark)
Christensen, Ove; Vistisen, Bo B.
1980-01-01
- frequency guitar function. The model predicts frequency responce of sound pressure and top plate mobility which are in close quantitative agreement with experimental responses. The absolute sound pressure level and mobility level are predicted to within a few decibels, and the equivalent piston area......The frequency response of sound pressure and top plate mobility is studied around the two first resonances of the guitar. These resonances are shown to result from a coupling between the fundamental top plate mode and the Helmholtz resonance of the cavity. A simple model is proposed for low...
Control architecture of power systems: Modeling of purpose and function
DEFF Research Database (Denmark)
Heussen, Kai; Saleem, Arshad; Lind, Morten
2009-01-01
Many new technologies with novel control capabilities have been developed in the context of “smart grid” research. However, often it is not clear how these capabilities should best be integrated in the overall system operation. New operation paradigms change the traditional control architecture...... of power systems and it is necessary to identify requirements and functions. How does new control architecture fit with the old architecture? How can power system functions be specified independent of technology? What is the purpose of control in power systems? In this paper, a method suitable...... for semantically consistent modeling of control architecture is presented. The method, called Multilevel Flow Modeling (MFM), is applied to the case of system balancing. It was found that MFM is capable of capturing implicit control knowledge, which is otherwise difficult to formalize. The method has possible...
The Use of Modeling Approach for Teaching Exponential Functions
Nunes, L. F.; Prates, D. B.; da Silva, J. M.
2017-12-01
This work presents a discussion related to the teaching and learning of mathematical contents related to the study of exponential functions in a freshman students group enrolled in the first semester of the Science and Technology Bachelor’s (STB of the Federal University of Jequitinhonha and Mucuri Valleys (UFVJM). As a contextualization tool strongly mentioned in the literature, the modelling approach was used as an educational teaching tool to produce contextualization in the teaching-learning process of exponential functions to these students. In this sense, were used some simple models elaborated with the GeoGebra software and, to have a qualitative evaluation of the investigation and the results, was used Didactic Engineering as a methodology research. As a consequence of this detailed research, some interesting details about the teaching and learning process were observed, discussed and described.
Directory of Open Access Journals (Sweden)
L.S. Ovcharenko
2017-10-01
Full Text Available Background. Scientific and technical progress, intensification of educational process and information overload have a negative effect on unformed central nervous system of primary schoolchildren, causing stress, which affects the increase in the incidence of recurrent upper respiratory tract infections (URTI and the functional state of the myocardium. In view of this, we analyzed a functional state of myocardium in children with recurrent URTI. The critical duration of the work of primary school child with electronic means of communication, which affects the quality of nighttime sleep and the nature of awakening in the morning, was established. We have studied the relationship of the above mentioned with the incidence of URTI, the level of school anxiety and functional reserve of the myocardium. The purpose of the study was to evaluate the functional reserve of the myocardium in children of primary school age, depending on the incidence of URTI and the level of psycho-emotional activity. Materials and methods. 239 children aged 6 to 9 years were examined. The analysis of the functional reserve of the myocardium was carried out in pupils with different incidence of the URTI, depending on the age. The influence of electronic communications on the quality of nighttime sleep and morning awakening was studied, and the level of school anxiety was evaluated. During the study, children were divided into two groups. Group 1 — children with recurrent acute respiratory diseases (n = 143. Group 2 — children who occasionally have URTI (n = 96. Results. Out of 239 children with recurrent acute respiratory infections, we have identified 173 children with reduced functional reserve of the myocardium (72.4 %. Among children with recurrent URTI, the incidence of reduced functional reserve of the myocardium was 76.2 %, and in occasionally ill children — 66.7 %. Children with recurrent URTI use electronic means of communication more often than
Using computational models to relate structural and functional brain connectivity
Czech Academy of Sciences Publication Activity Database
Hlinka, Jaroslav; Coombes, S.
2012-01-01
Roč. 36, č. 2 (2012), s. 2137-2145 ISSN 0953-816X R&D Projects: GA MŠk 7E08027 EU Projects: European Commission(XE) 200728 - BRAINSYNC Institutional research plan: CEZ:AV0Z10300504 Keywords : brain disease * computational modelling * functional connectivity * graph theory * structural connectivity Subject RIV: FH - Neurology Impact factor: 3.753, year: 2012
A review of function modeling: Approaches and applications
Erden, M.S.; Komoto, H.; Van Beek, T.J.; D'Amelio, V.; Echavarria, E.; Tomiyama, T.
2008-01-01
This work is aimed at establishing a common frame and understanding of function modeling (FM) for our ongoing research activities. A comparative review of the literature is performed to grasp the various FM approaches with their commonalities and differences. The relations of FM with the research fields of artificial intelligence, design theory, and maintenance are discussed. In this discussion the goals are to highlight the features of various classical approaches in relation to FM, to delin...
Correlation functions and Schwinger-Dyson equations for Penner's model
International Nuclear Information System (INIS)
Chair, N.; Panda, S.
1991-05-01
The free energy of Penner's model exhibits logarithmic singularity in the continuum limit. We show, however, that the one and two point correlators of the usual loop-operators do not exhibit logarithmic singularity. The continuum Schwinger-Dyson equations involving these correlation functions are derived and it is found that within the space of the corresponding couplings, the resulting constraints obey a Virasoro algebra. The puncture operator having the correct (logarithmic) scaling behaviour is identified. (author). 13 refs
Model Complexities of Shallow Networks Representing Highly Varying Functions
Czech Academy of Sciences Publication Activity Database
Kůrková, Věra; Sanguineti, M.
2016-01-01
Roč. 171, 1 January (2016), s. 598-604 ISSN 0925-2312 R&D Projects: GA MŠk(CZ) LD13002 Grant - others:grant for Visiting Professors(IT) GNAMPA-INdAM Institutional support: RVO:67985807 Keywords : shallow networks * model complexity * highly varying functions * Chernoff bound * perceptrons * Gaussian kernel units Subject RIV: IN - Informatics, Computer Science Impact factor: 3.317, year: 2016
Linking density functional and mode coupling models for supercooled liquids
Energy Technology Data Exchange (ETDEWEB)
Premkumar, Leishangthem; Bidhoodi, Neeta; Das, Shankar P. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)
2016-03-28
We compare predictions from two familiar models of the metastable supercooled liquid, respectively, constructed with thermodynamic and dynamic approaches. In the so called density functional theory the free energy F[ρ] of the liquid is a functional of the inhomogeneous density ρ(r). The metastable state is identified as a local minimum of F[ρ]. The sharp density profile characterizing ρ(r) is identified as a single particle oscillator, whose frequency is obtained from the parameters of the optimum density function. On the other hand, a dynamic approach to supercooled liquids is taken in the mode coupling theory (MCT) which predict a sharp ergodicity-non-ergodicity transition at a critical density. The single particle dynamics in the non-ergodic state, treated approximately, represents a propagating mode whose characteristic frequency is computed from the corresponding memory function of the MCT. The mass localization parameters in the above two models (treated in their simplest forms) are obtained, respectively, in terms of the corresponding natural frequencies depicted and are shown to have comparable magnitudes.
Linking density functional and mode coupling models for supercooled liquids.
Premkumar, Leishangthem; Bidhoodi, Neeta; Das, Shankar P
2016-03-28
We compare predictions from two familiar models of the metastable supercooled liquid, respectively, constructed with thermodynamic and dynamic approaches. In the so called density functional theory the free energy F[ρ] of the liquid is a functional of the inhomogeneous density ρ(r). The metastable state is identified as a local minimum of F[ρ]. The sharp density profile characterizing ρ(r) is identified as a single particle oscillator, whose frequency is obtained from the parameters of the optimum density function. On the other hand, a dynamic approach to supercooled liquids is taken in the mode coupling theory (MCT) which predict a sharp ergodicity-non-ergodicity transition at a critical density. The single particle dynamics in the non-ergodic state, treated approximately, represents a propagating mode whose characteristic frequency is computed from the corresponding memory function of the MCT. The mass localization parameters in the above two models (treated in their simplest forms) are obtained, respectively, in terms of the corresponding natural frequencies depicted and are shown to have comparable magnitudes.
Transposons As Tools for Functional Genomics in Vertebrate Models.
Kawakami, Koichi; Largaespada, David A; Ivics, Zoltán
2017-11-01
Genetic tools and mutagenesis strategies based on transposable elements are currently under development with a vision to link primary DNA sequence information to gene functions in vertebrate models. By virtue of their inherent capacity to insert into DNA, transposons can be developed into powerful tools for chromosomal manipulations. Transposon-based forward mutagenesis screens have numerous advantages including high throughput, easy identification of mutated alleles, and providing insight into genetic networks and pathways based on phenotypes. For example, the Sleeping Beauty transposon has become highly instrumental to induce tumors in experimental animals in a tissue-specific manner with the aim of uncovering the genetic basis of diverse cancers. Here, we describe a battery of mutagenic cassettes that can be applied in conjunction with transposon vectors to mutagenize genes, and highlight versatile experimental strategies for the generation of engineered chromosomes for loss-of-function as well as gain-of-function mutagenesis for functional gene annotation in vertebrate models, including zebrafish, mice, and rats. Copyright © 2017 Elsevier Ltd. All rights reserved.