Pancreatic exocrine insufficiency(PEI) occurs when the insufficient secretion or function of pancreatic enzymes leads to maldigestion, most commonly as a result of chronic pancreatitis and pancreatic cancer. The condi...Pancreatic exocrine insufficiency(PEI) occurs when the insufficient secretion or function of pancreatic enzymes leads to maldigestion, most commonly as a result of chronic pancreatitis and pancreatic cancer. The condition is associated with significant morbidity and reductions in quality of life, even in milder forms. The challenges in approaching this condition include the non-specific presentation of mild to moderate PEI, and the lack of a convenient, accurate diagnostic test in this cohort. Classical symptoms appear late in the disease, and the diagnosis should be considered before steatorrhoea develops. Direct pancreatic function tests are the reference standard for diagnosis, but are invasive and not widely available. The faecal elastase-1(FE-1) stool test is widely available and has been shown to be as effective as the 13 C-mixed triglyceride breath test in more advanced disease. We recommend a pragmatic diagnostic approach that combines clinical history, assessment of nutritional status and measurement of FE-1. The critical first step is to consider the diagnosis. Once the diagnosis is confirmed, pancreatic enzyme replacement therapy should be initiated. The variety of enzyme preparations and recommended dosing regimens can present a challenge when selecting an adequate initial dose. Non-response should be actively sought and addressed in a systematic manner. This article discusses these challenges, and presents a practical approach to the diagnosis and management of PEI.展开更多
In this article, the restricted almost unbiased ridge logistic estimator (RAURLE) is proposed to estimate the parameter in a logistic regression model with exact linear re-strictions when there exists multicollinearit...In this article, the restricted almost unbiased ridge logistic estimator (RAURLE) is proposed to estimate the parameter in a logistic regression model with exact linear re-strictions when there exists multicollinearity among explanatory variables. The performance of the proposed estimator over the maximum likelihood estimator (MLE), ridge logistic estimator (RLE), almost unbiased ridge logistic estimator (AURLE), and restricted maximum likelihood estimator (RMLE) with respect to different ridge parameters is investigated through a simulation study in terms of scalar mean square error.展开更多
In the presence of multicollinearity in logistic regression, the variance of the Maximum Likelihood Estimator (MLE) becomes inflated. Siray et al. (2015) [1] proposed a restricted Liu estimator in logistic regression ...In the presence of multicollinearity in logistic regression, the variance of the Maximum Likelihood Estimator (MLE) becomes inflated. Siray et al. (2015) [1] proposed a restricted Liu estimator in logistic regression model with exact linear restrictions. However, there are some situations, where the linear restrictions are stochastic. In this paper, we propose a Stochastic Restricted Maximum Likelihood Estimator (SRMLE) for the logistic regression model with stochastic linear restrictions to overcome this issue. Moreover, a Monte Carlo simulation is conducted for comparing the performances of the MLE, Restricted Maximum Likelihood Estimator (RMLE), Ridge Type Logistic Estimator(LRE), Liu Type Logistic Estimator(LLE), and SRMLE for the logistic regression model by using Scalar Mean Squared Error (SMSE).展开更多
Cochlear implants can successfully provide auditory information for bilaterally profoundly deaf patients by electrically stimulating auditory nerve fibres via an electrode array, which is surgically implanted into the...Cochlear implants can successfully provide auditory information for bilaterally profoundly deaf patients by electrically stimulating auditory nerve fibres via an electrode array, which is surgically implanted into the scala tympani of the cochlea. It is therefore important that the electrode array does not cause damage to the fine intracochlear structures during the process of insertion, as this can result in the loss of spiral ganglion cells, which are necessary for the implant to evoke auditory percepts. There is strong evidence that trauma and damage during insertion of electrode arrays into the human cochlea are related to the stiffness of the electrode array. Previous studies were conducted to experimentally determine the stiffness properties of electrode arrays using three-point flexural bending and buckling tests.In this paper, the design of nucleus straight electrode array is modified to give a greater flexibility to further reduce the risk of trauma to delicate structures of the cochlea during surgical insertion of the electrode array. This is achieved by reducing the cross-sectional area of the electrode array at selected positions over its length. Improvements in the flexibility of the new straight electrode array and the bending behavior at its tip have been demonstrated using finite element analysis. Loads applied to the tip of the electrode array at different angles with respect to the longitudinal axis of the electrode array showed that the modified design caused the tip to be more flexible and therefore better able to curl around the inner spiral of the scala tympani and thus less likely to penetrate the basilar membrane during insertion. Loads applied at other positions along the electrode array showed that bending occurred more readily using the modified design thereby reducing the friction and shear stresses at the contact interface between the electrode array and the delicate cochlea structures.展开更多
文摘Pancreatic exocrine insufficiency(PEI) occurs when the insufficient secretion or function of pancreatic enzymes leads to maldigestion, most commonly as a result of chronic pancreatitis and pancreatic cancer. The condition is associated with significant morbidity and reductions in quality of life, even in milder forms. The challenges in approaching this condition include the non-specific presentation of mild to moderate PEI, and the lack of a convenient, accurate diagnostic test in this cohort. Classical symptoms appear late in the disease, and the diagnosis should be considered before steatorrhoea develops. Direct pancreatic function tests are the reference standard for diagnosis, but are invasive and not widely available. The faecal elastase-1(FE-1) stool test is widely available and has been shown to be as effective as the 13 C-mixed triglyceride breath test in more advanced disease. We recommend a pragmatic diagnostic approach that combines clinical history, assessment of nutritional status and measurement of FE-1. The critical first step is to consider the diagnosis. Once the diagnosis is confirmed, pancreatic enzyme replacement therapy should be initiated. The variety of enzyme preparations and recommended dosing regimens can present a challenge when selecting an adequate initial dose. Non-response should be actively sought and addressed in a systematic manner. This article discusses these challenges, and presents a practical approach to the diagnosis and management of PEI.
文摘In this article, the restricted almost unbiased ridge logistic estimator (RAURLE) is proposed to estimate the parameter in a logistic regression model with exact linear re-strictions when there exists multicollinearity among explanatory variables. The performance of the proposed estimator over the maximum likelihood estimator (MLE), ridge logistic estimator (RLE), almost unbiased ridge logistic estimator (AURLE), and restricted maximum likelihood estimator (RMLE) with respect to different ridge parameters is investigated through a simulation study in terms of scalar mean square error.
文摘In the presence of multicollinearity in logistic regression, the variance of the Maximum Likelihood Estimator (MLE) becomes inflated. Siray et al. (2015) [1] proposed a restricted Liu estimator in logistic regression model with exact linear restrictions. However, there are some situations, where the linear restrictions are stochastic. In this paper, we propose a Stochastic Restricted Maximum Likelihood Estimator (SRMLE) for the logistic regression model with stochastic linear restrictions to overcome this issue. Moreover, a Monte Carlo simulation is conducted for comparing the performances of the MLE, Restricted Maximum Likelihood Estimator (RMLE), Ridge Type Logistic Estimator(LRE), Liu Type Logistic Estimator(LLE), and SRMLE for the logistic regression model by using Scalar Mean Squared Error (SMSE).
文摘Cochlear implants can successfully provide auditory information for bilaterally profoundly deaf patients by electrically stimulating auditory nerve fibres via an electrode array, which is surgically implanted into the scala tympani of the cochlea. It is therefore important that the electrode array does not cause damage to the fine intracochlear structures during the process of insertion, as this can result in the loss of spiral ganglion cells, which are necessary for the implant to evoke auditory percepts. There is strong evidence that trauma and damage during insertion of electrode arrays into the human cochlea are related to the stiffness of the electrode array. Previous studies were conducted to experimentally determine the stiffness properties of electrode arrays using three-point flexural bending and buckling tests.In this paper, the design of nucleus straight electrode array is modified to give a greater flexibility to further reduce the risk of trauma to delicate structures of the cochlea during surgical insertion of the electrode array. This is achieved by reducing the cross-sectional area of the electrode array at selected positions over its length. Improvements in the flexibility of the new straight electrode array and the bending behavior at its tip have been demonstrated using finite element analysis. Loads applied to the tip of the electrode array at different angles with respect to the longitudinal axis of the electrode array showed that the modified design caused the tip to be more flexible and therefore better able to curl around the inner spiral of the scala tympani and thus less likely to penetrate the basilar membrane during insertion. Loads applied at other positions along the electrode array showed that bending occurred more readily using the modified design thereby reducing the friction and shear stresses at the contact interface between the electrode array and the delicate cochlea structures.
