The main objective of this paper is to consider model averaging methods for kriging models.This paper proposes a Mallows model averaging procedure for the orthogonal kriging model and demonstrate the asymptotic optima...The main objective of this paper is to consider model averaging methods for kriging models.This paper proposes a Mallows model averaging procedure for the orthogonal kriging model and demonstrate the asymptotic optimality of the model averaging estimators in terms of mean square error.Simulation studies are conducted to evaluate the performance of the proposed method and compare it with the competitors to demonstrate its superiority.The authors also analyse a real dataset for an illustration.展开更多
Longitudinal trends of observations can be estimated using the generalized multivariate analysis of variance (GMANOVA) model proposed by [10]. In the present paper, we consider estimating the trends nonparametrically ...Longitudinal trends of observations can be estimated using the generalized multivariate analysis of variance (GMANOVA) model proposed by [10]. In the present paper, we consider estimating the trends nonparametrically using known basis functions. Then, as in nonparametric regression, an overfitting problem occurs. [13] showed that the GMANOVA model is equivalent to the varying coefficient model with non-longitudinal covariates. Hence, as in the case of the ordinary linear regression model, when the number of covariates becomes large, the estimator of the varying coefficient becomes unstable. In the present paper, we avoid the overfitting problem and the instability problem by applying the concept behind penalized smoothing spline regression and multivariate generalized ridge regression. In addition, we propose two criteria to optimize hyper parameters, namely, a smoothing parameter and ridge parameters. Finally, we compare the ordinary least square estimator and the new estimator.展开更多
Frequentist model averaging has received much attention from econometricians and statisticians in recent years.A key problem with frequentist model average estimators is the choice of weights.This paper develops a new...Frequentist model averaging has received much attention from econometricians and statisticians in recent years.A key problem with frequentist model average estimators is the choice of weights.This paper develops a new approach of choosing weights based on an approximation of generalized cross validation.The resultant least squares model average estimators are proved to be asymptotically optimal in the sense of achieving the lowest possible squared errors.Especially,the optimality is built under both discrete and continuous weigh sets.Compared with the existing approach based on Mallows criterion,the conditions required for the asymptotic optimality of the proposed method are more reasonable.Simulation studies and real data application show good performance of the proposed estimators.展开更多
The varying-coefficient single-index model(VCSIM)is widely used in economics,statistics and biology.A model averaging method for VCSIM based on a Mallows-type criterion is proposed to improve prodictive capacity,which...The varying-coefficient single-index model(VCSIM)is widely used in economics,statistics and biology.A model averaging method for VCSIM based on a Mallows-type criterion is proposed to improve prodictive capacity,which allows the number of candidate models to diverge with sample size.Under model misspecification,the asymptotic optimality is derived in the sense of achieving the lowest possible squared errors.The authors compare the proposed model averaging method with several other classical model selection methods by simulations and the corresponding results show that the model averaging estimation has a outstanding performance.The authors also apply the method to a real dataset.展开更多
Corchorus olitorius (Jew’s mallow), is one of the African indigenous leafy vegetables increasingly getting attention as a possible contributor of both micronutrients and bioactive compounds including proteins, lipids...Corchorus olitorius (Jew’s mallow), is one of the African indigenous leafy vegetables increasingly getting attention as a possible contributor of both micronutrients and bioactive compounds including proteins, lipids, fiber and vitamin C to human nutrition. Leaves of Corchorus olitorius have been found to have high level of phytochemicals: flavonoids, polyphenols, tannins, and saponins that possess strong radical scavenging activity and antioxidant power. In the arid and semi-arid areas of the world, drought is the main limiting factor affecting plant productivity and influences almost all aspects of plant biology. Water stress deficit is known to cause oxidative stress condition that has generally been reported to elevate phenolic antioxidants in various crops including Jew’s mallow. On the other hand, fertilization is crucial for crop management and high yield, it also affects nutritional value of the food plants. Nitrogen (N) fertilization affects health and nutritional value, including mineral content, fatty acid profile, anti-oxidative capacity and polyphenol levels and composition. The possible effects of fertilization should be considered when deciding on fertilization regime, to optimize both plant physiology, productivity and food-related effects. Nitrogen is an important element for Jew’s mallow production since it responds well to it. However, appropriate amounts of nutrients need to be provided to crops at the right time to favor both crop growth, yield and quality. Different reports confirmed that addition or increase of N, negatively affects the total phenolics and total flavonoids, and reduces accumulation of defense-related secondary metabolites resulting in lower oxidative capacity. Increased secondary metabolite production during water deficit and low nitrogen in the soil has been reported as a stress mechanism by most plants. However, further research is required to explore the biochemical response of Jew’s mallow to water deficit and nitrogen fertilization.展开更多
Jute mallow is a nutritious leafy vegetable. The leaves are rich in proteins, vitamins and essential amino acids. Molecular characterization of Jute mallow with focus on improvement of leaf yield is scarcely reported....Jute mallow is a nutritious leafy vegetable. The leaves are rich in proteins, vitamins and essential amino acids. Molecular characterization of Jute mallow with focus on improvement of leaf yield is scarcely reported. In the present study, inter sequence simple repeats (ISSR) molecular markers were employed to assess genetic diversity and relationships of 83 accessions of Jute mallow from different parts of Africa and Asia conserved at the World Vegetable Center East and Southern Africa. A total of 89 bands were amplified by 8 ISSR primers. Number of polymorphic bands per primer ranged from 2 to 6 with an average of 2.75 bands per primer. Polymorphic information content (PIC) values ranged from 0.390 to 0.760 with average of 0.53. Average Nei’s gene diversity (h) and Shannon’s information index (I) were 0.335 and 0.494 respectively. The highest pairwise genetic distance was 0.431 observed in a population from East Africa accessions. PC1 and PC2 axis explained 21.69% and 11.66% of the total variation respectively. UPGMA cluster analysis grouped the accessions into six main clusters at genetic similarity coefficient of 0.53 as standard value for classification. These results have important implications for jute mallow breeding and conservation.展开更多
BACKGROUND： Xerostomia is one of the most common side effects of radiation therapy among patients with head and neck cancers （HNC）. However, conventional medicine lacks an effective treatment for radiation-induced ...BACKGROUND： Xerostomia is one of the most common side effects of radiation therapy among patients with head and neck cancers （HNC）. However, conventional medicine lacks an effective treatment for radiation-induced xerostomia. OBJECTIVE： Synthesizing the traditional use ofAIcea digitata and Malva sylvestris with their known beneficial effects from recent studies, we evaluated the efficacy of the herbs in the quality of life （QOL） of HNC patients with radiation-induced xerostomia. DESIGN, SETTING, PARTICIPANTS AND INTERVENTIONS： This study is a randomized, double-arm, open-label active-controlled clinical trial. We evaluated the effect ofA. digitata and M. sy/vestris on QOL of HNC patients with radiation-induced xerostomia compared with Hypozalix （artificial saliva）. Patients were enrolled from the Imam Hossein Hospital＇s oncology clinic in Shahid Beheshti University of Medica Sciences. Tehran, Iran. MAIN OUTCOME MEASURES： Primary outcome measures in this trial were changes in patients＇ QOL assessed by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, Head and Neck Module （EORTC QLQ-H＆N 35）. RESULTS： Between-group analysis showed that the intervention group patients obtained significantly lower （better） total EORTC QLQ-H＆N 35 scores as compared to the control group at the end of the intervention period （P = 0.007）. Mean scores of dry mouth of EORTC QLQ-H＆N 35 was also significantly lower （better） in the intervention group as compared to the control group （P = 0.017）.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.11871294。
文摘The main objective of this paper is to consider model averaging methods for kriging models.This paper proposes a Mallows model averaging procedure for the orthogonal kriging model and demonstrate the asymptotic optimality of the model averaging estimators in terms of mean square error.Simulation studies are conducted to evaluate the performance of the proposed method and compare it with the competitors to demonstrate its superiority.The authors also analyse a real dataset for an illustration.
文摘Longitudinal trends of observations can be estimated using the generalized multivariate analysis of variance (GMANOVA) model proposed by [10]. In the present paper, we consider estimating the trends nonparametrically using known basis functions. Then, as in nonparametric regression, an overfitting problem occurs. [13] showed that the GMANOVA model is equivalent to the varying coefficient model with non-longitudinal covariates. Hence, as in the case of the ordinary linear regression model, when the number of covariates becomes large, the estimator of the varying coefficient becomes unstable. In the present paper, we avoid the overfitting problem and the instability problem by applying the concept behind penalized smoothing spline regression and multivariate generalized ridge regression. In addition, we propose two criteria to optimize hyper parameters, namely, a smoothing parameter and ridge parameters. Finally, we compare the ordinary least square estimator and the new estimator.
基金by National Key R&D Program of China(2020AAA0105200)the Ministry of Science and Technology of China(Grant no.2016YFB0502301)+1 种基金the National Natural Science Foundation of China(Grant nos.11871294,12031016,11971323,71925007,72042019,72091212 and 12001559)a joint grant from the Academy for Multidisciplinary Studies,Capital Normal University.
文摘Frequentist model averaging has received much attention from econometricians and statisticians in recent years.A key problem with frequentist model average estimators is the choice of weights.This paper develops a new approach of choosing weights based on an approximation of generalized cross validation.The resultant least squares model average estimators are proved to be asymptotically optimal in the sense of achieving the lowest possible squared errors.Especially,the optimality is built under both discrete and continuous weigh sets.Compared with the existing approach based on Mallows criterion,the conditions required for the asymptotic optimality of the proposed method are more reasonable.Simulation studies and real data application show good performance of the proposed estimators.
基金supported by the National Nature Science Foundation of Chinaunder Grant Nos.12001559and 11971324+1 种基金the Ministry of Education of Humanities and Social Science projectunder Grant No.19YJC910008。
文摘The varying-coefficient single-index model(VCSIM)is widely used in economics,statistics and biology.A model averaging method for VCSIM based on a Mallows-type criterion is proposed to improve prodictive capacity,which allows the number of candidate models to diverge with sample size.Under model misspecification,the asymptotic optimality is derived in the sense of achieving the lowest possible squared errors.The authors compare the proposed model averaging method with several other classical model selection methods by simulations and the corresponding results show that the model averaging estimation has a outstanding performance.The authors also apply the method to a real dataset.
文摘Corchorus olitorius (Jew’s mallow), is one of the African indigenous leafy vegetables increasingly getting attention as a possible contributor of both micronutrients and bioactive compounds including proteins, lipids, fiber and vitamin C to human nutrition. Leaves of Corchorus olitorius have been found to have high level of phytochemicals: flavonoids, polyphenols, tannins, and saponins that possess strong radical scavenging activity and antioxidant power. In the arid and semi-arid areas of the world, drought is the main limiting factor affecting plant productivity and influences almost all aspects of plant biology. Water stress deficit is known to cause oxidative stress condition that has generally been reported to elevate phenolic antioxidants in various crops including Jew’s mallow. On the other hand, fertilization is crucial for crop management and high yield, it also affects nutritional value of the food plants. Nitrogen (N) fertilization affects health and nutritional value, including mineral content, fatty acid profile, anti-oxidative capacity and polyphenol levels and composition. The possible effects of fertilization should be considered when deciding on fertilization regime, to optimize both plant physiology, productivity and food-related effects. Nitrogen is an important element for Jew’s mallow production since it responds well to it. However, appropriate amounts of nutrients need to be provided to crops at the right time to favor both crop growth, yield and quality. Different reports confirmed that addition or increase of N, negatively affects the total phenolics and total flavonoids, and reduces accumulation of defense-related secondary metabolites resulting in lower oxidative capacity. Increased secondary metabolite production during water deficit and low nitrogen in the soil has been reported as a stress mechanism by most plants. However, further research is required to explore the biochemical response of Jew’s mallow to water deficit and nitrogen fertilization.
文摘Jute mallow is a nutritious leafy vegetable. The leaves are rich in proteins, vitamins and essential amino acids. Molecular characterization of Jute mallow with focus on improvement of leaf yield is scarcely reported. In the present study, inter sequence simple repeats (ISSR) molecular markers were employed to assess genetic diversity and relationships of 83 accessions of Jute mallow from different parts of Africa and Asia conserved at the World Vegetable Center East and Southern Africa. A total of 89 bands were amplified by 8 ISSR primers. Number of polymorphic bands per primer ranged from 2 to 6 with an average of 2.75 bands per primer. Polymorphic information content (PIC) values ranged from 0.390 to 0.760 with average of 0.53. Average Nei’s gene diversity (h) and Shannon’s information index (I) were 0.335 and 0.494 respectively. The highest pairwise genetic distance was 0.431 observed in a population from East Africa accessions. PC1 and PC2 axis explained 21.69% and 11.66% of the total variation respectively. UPGMA cluster analysis grouped the accessions into six main clusters at genetic similarity coefficient of 0.53 as standard value for classification. These results have important implications for jute mallow breeding and conservation.
文摘BACKGROUND： Xerostomia is one of the most common side effects of radiation therapy among patients with head and neck cancers （HNC）. However, conventional medicine lacks an effective treatment for radiation-induced xerostomia. OBJECTIVE： Synthesizing the traditional use ofAIcea digitata and Malva sylvestris with their known beneficial effects from recent studies, we evaluated the efficacy of the herbs in the quality of life （QOL） of HNC patients with radiation-induced xerostomia. DESIGN, SETTING, PARTICIPANTS AND INTERVENTIONS： This study is a randomized, double-arm, open-label active-controlled clinical trial. We evaluated the effect ofA. digitata and M. sy/vestris on QOL of HNC patients with radiation-induced xerostomia compared with Hypozalix （artificial saliva）. Patients were enrolled from the Imam Hossein Hospital＇s oncology clinic in Shahid Beheshti University of Medica Sciences. Tehran, Iran. MAIN OUTCOME MEASURES： Primary outcome measures in this trial were changes in patients＇ QOL assessed by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, Head and Neck Module （EORTC QLQ-H＆N 35）. RESULTS： Between-group analysis showed that the intervention group patients obtained significantly lower （better） total EORTC QLQ-H＆N 35 scores as compared to the control group at the end of the intervention period （P = 0.007）. Mean scores of dry mouth of EORTC QLQ-H＆N 35 was also significantly lower （better） in the intervention group as compared to the control group （P = 0.017）.
