Background:Research on therapeutic processes has explored the elements that enhance psychotherapy’s effectiveness,particularly the role of common factors across various models.The therapist’s use of directiveness an...Background:Research on therapeutic processes has explored the elements that enhance psychotherapy’s effectiveness,particularly the role of common factors across various models.The therapist’s use of directiveness and support,as common variables,is crucial for effective treatment.Effective therapists adapt their level of directiveness and support according to the treatment phase,the issue being addressed,and the patient’s characteristics.This study examines the importance therapists attribute to directiveness and support,as well as its relationship with theoretical orientation,access to research publications,and stance on the similar effectiveness of different psychotherapeutic models.It aims to determine whether therapists’attributions regarding this variable are in line with the importance it is given in process research.Methods:Responses from 69 psychotherapists to the Psychotherapeutic Effectiveness Attribution Questionnaire(PEAQ-12),which assesses the importance therapists place on key psychotherapeutic process variables,including the directiveness and support provided,were analyzed.Theoretical orientations,ages,and experience levels were considered.Non-parametric tests,contingency tables,χ^(2)tests,t-tests,and ANOVAs were used to assess the variation in responses.Results:Common factors were often identified as key contributors to therapeutic healing,though these differences were not statistically significant(χ^(2)(2,N=67)=3.701,p=0.157).For the“directiveness and support from the therapist”variable,significant differences were observed:Cognitive-behavioral therapists valued directiveness and support more than psychodynamic therapists(t(20)=−3.569,p=0.002;Cohen’s d=1.18).Therapists who view cognitive-behavioral therapies as most effective also rated this variable higher(t(38)=3.816,p<0.001;Cohen’s d=1.21).Those regularly accessing specialized psychotherapy research publications valued this variable less than those who do so occasionally(t(64)=−2.693,p=0.009;Cohen’s d=0.65).Therapists who support the similar effectiveness of different models tend to favor common factors,including directiveness and support(χ^(2)(2,N=66)=12.522,p=0.002).Conclusions:Therapists express doubts about the factors influencing psychotherapy’s effectiveness,reflecting the ongoing debate.They align their views on the importance of directiveness and support with their theoretical orientation and positioning on the similar effectiveness of psychotherapies.The importance of analyzing therapists’attributions about the factors responsible for therapeutic change is emphasized,which will impact clinical practice.Advocacy for therapist flexibility and adaptation of therapy to the patient’s needs,including the level of directiveness and support provided,has been shown to be essential for effective psychotherapy.展开更多
This study investigates the degree of capital mobility in a panel of 16 Latin American and 4 Caribbean countries during 1960 to 2017 against the backdrop of the Feldstein-Horioka hypothesis by applying recent panel da...This study investigates the degree of capital mobility in a panel of 16 Latin American and 4 Caribbean countries during 1960 to 2017 against the backdrop of the Feldstein-Horioka hypothesis by applying recent panel data techniques.This is the first study on capital mobility in Latin American and Caribbean countries to employ the recently developed panel data procedure of the dynamic common correlated effects modeling technique of Chudik and Pesaran(J Econ 188:393–420,2015)and the error-correction testing of Gengenbach,Urbain,and Westerlund(Panel error correction testing with global stochastic trends,2008,J Appl Econ 31:982–1004,2016).These approaches address the serious panel data econometric issues of crosssection dependence,slope heterogeneity,nonstationarity,and endogeneity in a multifactor error-structure framework.The empirical findings of this study reveal a low average(mean)savings–retention coefficient for the panel as a whole and for most individual countries,as well as indicating a cointegration relationship between saving and investment ratios.The results indicate that there is a relatively high degree of capital mobility in the Latin American and Caribbean countries in the short run,while the long-run solvency condition is maintained,which is due to reduced frictions in goods and services markets causing increase competition.Increased capital mobility in these countries can promote economic growth and hasten the process of globalization by creating a conducive economic environment for FDI in these countries.展开更多
This paper aims to treat a study of generators of the cyclic group of higher even, odd, and prime order for composition being multiplication. In fact we developed order of a group, order of element of a group and gene...This paper aims to treat a study of generators of the cyclic group of higher even, odd, and prime order for composition being multiplication. In fact we developed order of a group, order of element of a group and generators of the cyclic group in real numbers. Also we express cyclic and generators of the group for composition in real numbers. Here we discuss the higher order of groups in different types of order, and generators of the cyclic group which will give us practical knowledge to see the applications of the composition. In order to find out the order of an element am∈Gin which an=e= identity element, then find Highest Common Factor i.e. (H.C.F) of mand n. When Gis a finite group, every element must have finite order but the converse is false. There are infinite groups where each element has a finite order. There may be more than one generator of a cyclic group. Also every cyclic group is necessarily abelian. But show that every infinite cyclic group contains only two generators. Finally, we find out the generators of the cyclic group of higher even, odd and prime order in different types of the group for composition being multiplication.展开更多
Introduction:Self-harm represents a significant public health challenge,particularly affecting young adults.This study evaluated prevalence rates and identified individual-and college-level risk factors for self-harm ...Introduction:Self-harm represents a significant public health challenge,particularly affecting young adults.This study evaluated prevalence rates and identified individual-and college-level risk factors for self-harm among college students in Jiangsu Province.Methods:Using data from the‘Surveillance for common disease and health risk factors among students in Jiangsu Province’program during 2019-2023,we employed multilevel logistic regression models to account for potential clustering within sampled colleges and to estimate odds ratios(OR)and 95%confidence intervals(CI)for person-and collegelevel factors.Dynamic analyses were conducted with repeated modeling by year.Results:Youth self-harm rates fluctuated between 2.21%and 3.83%during the study period.Self-harm was strongly associated with unhealthy lifestyles,particularly internet addiction(OR:2.50,95%CI:1.91,3.24),while regular family psychological forums were associated with decreased risk(OR:0.72,95%CI:0.55,0.95).Conclusion:Our findings emphasize the necessity of on-campus psychosocial support and highlight the importance of leveraging family-college collective resources with targeted interventions,especially for high-risk groups exhibiting unhealthy lifestyles,particularly internet addiction.展开更多
In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues...In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues of cross-sectional dependence, and introduces the concepts of weak and strong cross-sectional dependence. Then, the main attention is primarily paid to spatial and factor approaches for modeling cross-sectional dependence for both linear and nonlinear （nonparametric and semiparametric） panel data models. Finally, we conclude with some speculations on future research directions.展开更多
This paper compares the impact of restricted measures on CSI 500 stock index futures market and its underlying spot market.It uses vector error correction(VECM)model and common factor analysis method to study the diff...This paper compares the impact of restricted measures on CSI 500 stock index futures market and its underlying spot market.It uses vector error correction(VECM)model and common factor analysis method to study the differences between the two markets before and after the restricted measures was implemented.This paper analyzes the price discovery function through three aspects,i.e.,response to new information,price ratio of new information,and price discovery contribution degree of two markets.Based on empirical results,it is clear that group one in the period of April 17th to September 2nd has an obvious price discovery function.However,group two in the period of September 7th to December 31th does not have.The result shows that stock index futures do have price discovery function to some extent.However,due to the impact of restrictive policies,the spot market price contribution may exceed the futures market in some special time periods,which implies that the price discovery function of CSI 500 stock index futures market is not stable.展开更多
If common factors jointly affect country stock markets, it is an indica- tion of global stock market integration. Common factors may affect some markets more/less than other markets, an indication of the degree of glo...If common factors jointly affect country stock markets, it is an indica- tion of global stock market integration. Common factors may affect some markets more/less than other markets, an indication of the degree of global stock market in- tegration/segmentation. In this paper, we study the integration of global stock mar- kets based on the returns on exchange traded funds （ETFs） for the US, Canada, UK, Germany, France, Italy, Australia and Japan. The relationship between country ETF returns and common risk factors may be time-varying across countries, and that favors a regime switching （RS） factor model for the dynamics of the country ETF returns. A RS factor model for the relationship between country ETF returns and common risk factors is fitted to daily data for the period from May 31, 2000 to March 31, 2014. We use the data to test a hierarchy of hypotheses on country ETF returns： （1） common factor exposure across all country ETFs and all regimes; （2） common factor exposure across some country ETFs and all regimes, and （3） common factor exposure across some country ETFs and some regimes. The RS factor model for ETF returns fits the data well and the common factors have variable effects across countries and over regimes展开更多
Secret sharing(SS)is part of the essential techniques in cryptography but still faces many challenges in efficiency and security.Currently,SS schemes based on the Chinese Remainder Theorem(CRT)are either low in the in...Secret sharing(SS)is part of the essential techniques in cryptography but still faces many challenges in efficiency and security.Currently,SS schemes based on the Chinese Remainder Theorem(CRT)are either low in the information rate or complicated in construction.To solve the above problems,1)a simple construction of an ideal(t,n)-SS scheme is proposed based on CRT for a polynomial ring.Compared with Ning’s scheme,it is much more efficient in generating n pairwise coprime modular polynomials during the scheme construction phase.Moreover,Shamir’s scheme is also a special case of our scheme.To further improve the security,2)a common-factor-based(t,n)-SS scheme is proposed in which all shareholders share a common polynomial factor.It enables both the verification of received shares and the establishment of a secure channel among shareholders during the reconstruction phase.As a result,the scheme is resistant to eavesdropping and modification attacks by outside adversaries.展开更多
We propose a new nonparametric approach to represent the linear dependence structure of a spatiotemporal process in terms of latent common factors.Though it is formally similar to the existing reduced rank approximati...We propose a new nonparametric approach to represent the linear dependence structure of a spatiotemporal process in terms of latent common factors.Though it is formally similar to the existing reduced rank approximation methods,the fundamental difference is that the low-dimensional structure is completely unknown in our setting,which is learned from the data collected irregularly over space but regularly in time.Furthermore,a graph Laplacian is incorporated in the learning in order to take the advantage of the continuity over space,and a new aggregation method via randomly partitioning space is introduced to improve the efficiency.We do not impose any stationarity conditions over space either,as the learning is facilitated by the stationarity in time.Krigings over space and time are carried out based on the learned low-dimensional structure,which is scalable to the cases when the data are taken over a large number of locations and/or over a long time period.Asymptotic properties of the proposed methods are established.An illustration with both simulated and real data sets is also reported.展开更多
This paper studies the estimation of the partially linear panel data models,allowing for cross-sectional dependence through a common factors structure.This semiparametric additive partial linear framework,including bo...This paper studies the estimation of the partially linear panel data models,allowing for cross-sectional dependence through a common factors structure.This semiparametric additive partial linear framework,including both linear and nonlinear additive components,is more flexible compared to linear models,and is preferred to a fully nonparametric regression because of the‘curse of dimensionality’.The consistency and asymptotic normality of the proposed estimators are established for the case where both cross-sectional dimension and temporal dimension go to infinity.The theoretical findings are further supported for small samples via a Monte Carlo study.The results suggest that the proposed method is robust to a wide variety of data generation processes.展开更多
Industrial production series are volatile and often cyclical. Time series models can be used toestablish certain stylized facts, such as trends and cycles, which may be present in these series. Incertain situations, i...Industrial production series are volatile and often cyclical. Time series models can be used toestablish certain stylized facts, such as trends and cycles, which may be present in these series. Incertain situations, it is also possible that common factors, which may have an interesting interpretation,can be detected in production series. Series from two neighboring countries with close economicrelationships, such as Germany and Austria, are especially likely to exhibit such joint stylized facts.展开更多
In this study, differentially expressed genes in peripheral blood from patients with Kashin-Beck disease and Keshan disease were compared to further investigate the etiology and pathogenesis of both diseases, which oc...In this study, differentially expressed genes in peripheral blood from patients with Kashin-Beck disease and Keshan disease were compared to further investigate the etiology and pathogenesis of both diseases, which occur in a common endemic area of China. Twenty Kashin-Beck disease patients and 12 healthy controls, and 16 Keshan disease patients and 16 healthy controls, were grouped into four pairs. Patients and controls were selected from common endemic areas for the two diseases. Total RNA was isolated from peripheral blood mononuclear cells from all patients and controls, and gene expression profiles analyzed by oligonucleotide microarrays. Sixteen genes differentially expressed in both Kashin-Beck disease and Keshan disease (versus controls) were identified, and comprised nine genes showing synchronous and seven asynchronous expression. The Comparative Toxicogenomics Database shows that expression and biological function of these genes can be affected by multiple environmental factors, including mycotoxin and selenium content, potential environmental risk factors for the two diseases. Thus, these shared differentially expressed genes may contribute to the distinct organ lesions, caused by common environmental risk factors of Kashin-Beck disease and Keshan disease.展开更多
文摘Background:Research on therapeutic processes has explored the elements that enhance psychotherapy’s effectiveness,particularly the role of common factors across various models.The therapist’s use of directiveness and support,as common variables,is crucial for effective treatment.Effective therapists adapt their level of directiveness and support according to the treatment phase,the issue being addressed,and the patient’s characteristics.This study examines the importance therapists attribute to directiveness and support,as well as its relationship with theoretical orientation,access to research publications,and stance on the similar effectiveness of different psychotherapeutic models.It aims to determine whether therapists’attributions regarding this variable are in line with the importance it is given in process research.Methods:Responses from 69 psychotherapists to the Psychotherapeutic Effectiveness Attribution Questionnaire(PEAQ-12),which assesses the importance therapists place on key psychotherapeutic process variables,including the directiveness and support provided,were analyzed.Theoretical orientations,ages,and experience levels were considered.Non-parametric tests,contingency tables,χ^(2)tests,t-tests,and ANOVAs were used to assess the variation in responses.Results:Common factors were often identified as key contributors to therapeutic healing,though these differences were not statistically significant(χ^(2)(2,N=67)=3.701,p=0.157).For the“directiveness and support from the therapist”variable,significant differences were observed:Cognitive-behavioral therapists valued directiveness and support more than psychodynamic therapists(t(20)=−3.569,p=0.002;Cohen’s d=1.18).Therapists who view cognitive-behavioral therapies as most effective also rated this variable higher(t(38)=3.816,p<0.001;Cohen’s d=1.21).Those regularly accessing specialized psychotherapy research publications valued this variable less than those who do so occasionally(t(64)=−2.693,p=0.009;Cohen’s d=0.65).Therapists who support the similar effectiveness of different models tend to favor common factors,including directiveness and support(χ^(2)(2,N=66)=12.522,p=0.002).Conclusions:Therapists express doubts about the factors influencing psychotherapy’s effectiveness,reflecting the ongoing debate.They align their views on the importance of directiveness and support with their theoretical orientation and positioning on the similar effectiveness of psychotherapies.The importance of analyzing therapists’attributions about the factors responsible for therapeutic change is emphasized,which will impact clinical practice.Advocacy for therapist flexibility and adaptation of therapy to the patient’s needs,including the level of directiveness and support provided,has been shown to be essential for effective psychotherapy.
文摘This study investigates the degree of capital mobility in a panel of 16 Latin American and 4 Caribbean countries during 1960 to 2017 against the backdrop of the Feldstein-Horioka hypothesis by applying recent panel data techniques.This is the first study on capital mobility in Latin American and Caribbean countries to employ the recently developed panel data procedure of the dynamic common correlated effects modeling technique of Chudik and Pesaran(J Econ 188:393–420,2015)and the error-correction testing of Gengenbach,Urbain,and Westerlund(Panel error correction testing with global stochastic trends,2008,J Appl Econ 31:982–1004,2016).These approaches address the serious panel data econometric issues of crosssection dependence,slope heterogeneity,nonstationarity,and endogeneity in a multifactor error-structure framework.The empirical findings of this study reveal a low average(mean)savings–retention coefficient for the panel as a whole and for most individual countries,as well as indicating a cointegration relationship between saving and investment ratios.The results indicate that there is a relatively high degree of capital mobility in the Latin American and Caribbean countries in the short run,while the long-run solvency condition is maintained,which is due to reduced frictions in goods and services markets causing increase competition.Increased capital mobility in these countries can promote economic growth and hasten the process of globalization by creating a conducive economic environment for FDI in these countries.
文摘This paper aims to treat a study of generators of the cyclic group of higher even, odd, and prime order for composition being multiplication. In fact we developed order of a group, order of element of a group and generators of the cyclic group in real numbers. Also we express cyclic and generators of the group for composition in real numbers. Here we discuss the higher order of groups in different types of order, and generators of the cyclic group which will give us practical knowledge to see the applications of the composition. In order to find out the order of an element am∈Gin which an=e= identity element, then find Highest Common Factor i.e. (H.C.F) of mand n. When Gis a finite group, every element must have finite order but the converse is false. There are infinite groups where each element has a finite order. There may be more than one generator of a cyclic group. Also every cyclic group is necessarily abelian. But show that every infinite cyclic group contains only two generators. Finally, we find out the generators of the cyclic group of higher even, odd and prime order in different types of the group for composition being multiplication.
基金Supported by National Social Science Foundation of China(Grant No.23CGL072),Ministry of Science and Technology(Grant No.G2023141005L),Ministry of Education(Grant No.1125000172)SEU Innovation Capability Enhancement Plan for Doctoral Students(Grant No.CXJH_SEU 25220)Jiangsu Provincial Department of Science and Technology,Jiangsu Provincial Social Science Foundation(Grant No.24SHB005).
文摘Introduction:Self-harm represents a significant public health challenge,particularly affecting young adults.This study evaluated prevalence rates and identified individual-and college-level risk factors for self-harm among college students in Jiangsu Province.Methods:Using data from the‘Surveillance for common disease and health risk factors among students in Jiangsu Province’program during 2019-2023,we employed multilevel logistic regression models to account for potential clustering within sampled colleges and to estimate odds ratios(OR)and 95%confidence intervals(CI)for person-and collegelevel factors.Dynamic analyses were conducted with repeated modeling by year.Results:Youth self-harm rates fluctuated between 2.21%and 3.83%during the study period.Self-harm was strongly associated with unhealthy lifestyles,particularly internet addiction(OR:2.50,95%CI:1.91,3.24),while regular family psychological forums were associated with decreased risk(OR:0.72,95%CI:0.55,0.95).Conclusion:Our findings emphasize the necessity of on-campus psychosocial support and highlight the importance of leveraging family-college collective resources with targeted interventions,especially for high-risk groups exhibiting unhealthy lifestyles,particularly internet addiction.
基金Supported by the National Natural Science Foundation of China(71131008(Key Project)and 71271179)
文摘In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues of cross-sectional dependence, and introduces the concepts of weak and strong cross-sectional dependence. Then, the main attention is primarily paid to spatial and factor approaches for modeling cross-sectional dependence for both linear and nonlinear （nonparametric and semiparametric） panel data models. Finally, we conclude with some speculations on future research directions.
文摘This paper compares the impact of restricted measures on CSI 500 stock index futures market and its underlying spot market.It uses vector error correction(VECM)model and common factor analysis method to study the differences between the two markets before and after the restricted measures was implemented.This paper analyzes the price discovery function through three aspects,i.e.,response to new information,price ratio of new information,and price discovery contribution degree of two markets.Based on empirical results,it is clear that group one in the period of April 17th to September 2nd has an obvious price discovery function.However,group two in the period of September 7th to December 31th does not have.The result shows that stock index futures do have price discovery function to some extent.However,due to the impact of restrictive policies,the spot market price contribution may exceed the futures market in some special time periods,which implies that the price discovery function of CSI 500 stock index futures market is not stable.
文摘If common factors jointly affect country stock markets, it is an indica- tion of global stock market integration. Common factors may affect some markets more/less than other markets, an indication of the degree of global stock market in- tegration/segmentation. In this paper, we study the integration of global stock mar- kets based on the returns on exchange traded funds （ETFs） for the US, Canada, UK, Germany, France, Italy, Australia and Japan. The relationship between country ETF returns and common risk factors may be time-varying across countries, and that favors a regime switching （RS） factor model for the dynamics of the country ETF returns. A RS factor model for the relationship between country ETF returns and common risk factors is fitted to daily data for the period from May 31, 2000 to March 31, 2014. We use the data to test a hierarchy of hypotheses on country ETF returns： （1） common factor exposure across all country ETFs and all regimes; （2） common factor exposure across some country ETFs and all regimes, and （3） common factor exposure across some country ETFs and some regimes. The RS factor model for ETF returns fits the data well and the common factors have variable effects across countries and over regimes
基金This work was supported by National Key R&D Project 2018YFB2100300the National Natural Science Foundation of China(Grant No.61520106007).
文摘Secret sharing(SS)is part of the essential techniques in cryptography but still faces many challenges in efficiency and security.Currently,SS schemes based on the Chinese Remainder Theorem(CRT)are either low in the information rate or complicated in construction.To solve the above problems,1)a simple construction of an ideal(t,n)-SS scheme is proposed based on CRT for a polynomial ring.Compared with Ning’s scheme,it is much more efficient in generating n pairwise coprime modular polynomials during the scheme construction phase.Moreover,Shamir’s scheme is also a special case of our scheme.To further improve the security,2)a common-factor-based(t,n)-SS scheme is proposed in which all shareholders share a common polynomial factor.It enables both the verification of received shares and the establishment of a secure channel among shareholders during the reconstruction phase.As a result,the scheme is resistant to eavesdropping and modification attacks by outside adversaries.
基金supported by National Statistical Research Project of China(Grant No.2015LY77)National Natural Science Foundation of China(Grant Nos.11571080,11571081,71531006 and 71672042)+3 种基金supported by Engineering and Physical Sciences Research Council(Grant No.EP/L01226X/1)supported by National Natural Science Foundation of China(Grant Nos.11371318 and 11771390)Zhejiang Province Natural Science Foundation(Grant No.R16A010001)the Fundamental Research Funds for the Central Universities。
文摘We propose a new nonparametric approach to represent the linear dependence structure of a spatiotemporal process in terms of latent common factors.Though it is formally similar to the existing reduced rank approximation methods,the fundamental difference is that the low-dimensional structure is completely unknown in our setting,which is learned from the data collected irregularly over space but regularly in time.Furthermore,a graph Laplacian is incorporated in the learning in order to take the advantage of the continuity over space,and a new aggregation method via randomly partitioning space is introduced to improve the efficiency.We do not impose any stationarity conditions over space either,as the learning is facilitated by the stationarity in time.Krigings over space and time are carried out based on the learned low-dimensional structure,which is scalable to the cases when the data are taken over a large number of locations and/or over a long time period.Asymptotic properties of the proposed methods are established.An illustration with both simulated and real data sets is also reported.
基金supported by the National Natural Science Foundation of China under Grant Nos.71703156,71988101,and 72073126。
文摘This paper studies the estimation of the partially linear panel data models,allowing for cross-sectional dependence through a common factors structure.This semiparametric additive partial linear framework,including both linear and nonlinear additive components,is more flexible compared to linear models,and is preferred to a fully nonparametric regression because of the‘curse of dimensionality’.The consistency and asymptotic normality of the proposed estimators are established for the case where both cross-sectional dimension and temporal dimension go to infinity.The theoretical findings are further supported for small samples via a Monte Carlo study.The results suggest that the proposed method is robust to a wide variety of data generation processes.
文摘Industrial production series are volatile and often cyclical. Time series models can be used toestablish certain stylized facts, such as trends and cycles, which may be present in these series. Incertain situations, it is also possible that common factors, which may have an interesting interpretation,can be detected in production series. Series from two neighboring countries with close economicrelationships, such as Germany and Austria, are especially likely to exhibit such joint stylized facts.
基金supported in part by the Key Scientific and Technological Innovation Special Projects of Shaanxi "13115" of China (2009ZDKG-79)the National Natural Science Foundation of China (30872192, 81273008)
文摘In this study, differentially expressed genes in peripheral blood from patients with Kashin-Beck disease and Keshan disease were compared to further investigate the etiology and pathogenesis of both diseases, which occur in a common endemic area of China. Twenty Kashin-Beck disease patients and 12 healthy controls, and 16 Keshan disease patients and 16 healthy controls, were grouped into four pairs. Patients and controls were selected from common endemic areas for the two diseases. Total RNA was isolated from peripheral blood mononuclear cells from all patients and controls, and gene expression profiles analyzed by oligonucleotide microarrays. Sixteen genes differentially expressed in both Kashin-Beck disease and Keshan disease (versus controls) were identified, and comprised nine genes showing synchronous and seven asynchronous expression. The Comparative Toxicogenomics Database shows that expression and biological function of these genes can be affected by multiple environmental factors, including mycotoxin and selenium content, potential environmental risk factors for the two diseases. Thus, these shared differentially expressed genes may contribute to the distinct organ lesions, caused by common environmental risk factors of Kashin-Beck disease and Keshan disease.
