Two new species of genus Diplopeltoides Gerlach,1962 and two new species of genus Minolaimus Vitiello,1970 were described based on recently collected specimens from marine sediments of the South China Sea and the East...Two new species of genus Diplopeltoides Gerlach,1962 and two new species of genus Minolaimus Vitiello,1970 were described based on recently collected specimens from marine sediments of the South China Sea and the East China Sea,respectively.Diplopeltoides conoicaudatus sp.nov.is characterized by annulated cuticle;tiny terminal buccal cavity;short cephalic setae about 2-μm long;loop-shaped amphideal fovea without sclerotized plate;slender and arcuate spicules;triangular gubernaculum possessing a small dorso-caudal apophysis;female with two opposed and reflexed ovaries.Diplopeltoides longifoveatus sp.nov.is characterized by its papilliform cephalic sensilla;long and narrow amphideal fovea with fine transverse striations;inverse S-shaped spicules with a dorsally bent manubrium;gubernaculum with dorso-caudal apophysis;cylindrical tail with round terminal end.Minolaimus multisupplementatus sp.nov.is characterized by cuticle with lateral differentiation of three longitudinal rows of large dots,spiral amphideal fovea with seven turns,pharynx cylindrical without posterior bulb,spicules arcuated with central lamella,gubernaculum arcuate and parallel to spicule,without dorso-caudal apophysis,a papilliform and 29 cup-shaped precloacal supplement;tail conical with long flagelliform portion.Minolaimus apicalis sp.nov.is characterized by cuticle with lateral differentiation of three longitudinal rows of larger dots from the middle of pharynx to the conical portion of tail and a longitudinal row of pores in the pharyngeal region and precloacal region;spiral amphidial fovea with four turns and close to anterior end;pharynx cylindrical with oval posterior bulb,spicules arcuated and proximal end bent dorsally,gubernaculum with a broad curved dorsal apophysis;two sucked-like and six cup-shaped cuticularized precloacal supplements;tail conico-cylindrical with slightly enlarged tip.Updated keys to species of Diplopeltoides and Minolaimus were provided.展开更多
In this paper, we propose a new estimation method for a nonparametric hidden Markov model(HMM), in which both the emission model and the transition matrix are nonparametric, and a semiparametric HMM, in which the tran...In this paper, we propose a new estimation method for a nonparametric hidden Markov model(HMM), in which both the emission model and the transition matrix are nonparametric, and a semiparametric HMM, in which the transition matrix is parametric while emission models are nonparametric. The estimation is based on a novel composite likelihood method, where the pairs of consecutive observations are treated as independent bivariate random variables. Therefore, the model is transformed into a mixture model, and a modified expectation-maximization(EM) algorithm is developed to compute the maximum composite likelihood.We systematically study asymptotic properties for both the nonparametric HMM and the semiparametric HMM. We also propose a generalized likelihood ratio test to choose between the nonparametric HMM and the semiparametric HMM. We derive the asymptotic distribution and prove the Wilk’s phenomenon of the proposed test statistics. Simulation studies and an application in volatility clustering analysis of the volatility index in the Chicago Board Options Exchange(CBOE) are conducted to demonstrate the effectiveness of the proposed methods.展开更多
Based on a representative survey of new college graduates in China,we present a job location choice model that allows for a self-selection effect in college regions by considering region-dependent heterogeneous prefer...Based on a representative survey of new college graduates in China,we present a job location choice model that allows for a self-selection effect in college regions by considering region-dependent heterogeneous preference for job locations and unobservable location features.We also treat endogenous housing costs using the method developed by Berry et al.(1995).Our estimation results show that college education significantly increases graduates'likelihood of working in the city where their college is located.However,a model that does not consider the self-selection effect overestimates this impact.The impact of college location on a graduate's migration decision varies considerably across cities.There is significant heterogeneity between students from universities of dijferent tiers and rural versus urban areas.Meanwhile,the graduates show a marked home preference when choosing their job locations,and they tend to avoid working in cities with high housing costs.These findings shed light on debates on place-based higher education policies and spatial distribution of human capital with a high level of education.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41176107,41676146)。
文摘Two new species of genus Diplopeltoides Gerlach,1962 and two new species of genus Minolaimus Vitiello,1970 were described based on recently collected specimens from marine sediments of the South China Sea and the East China Sea,respectively.Diplopeltoides conoicaudatus sp.nov.is characterized by annulated cuticle;tiny terminal buccal cavity;short cephalic setae about 2-μm long;loop-shaped amphideal fovea without sclerotized plate;slender and arcuate spicules;triangular gubernaculum possessing a small dorso-caudal apophysis;female with two opposed and reflexed ovaries.Diplopeltoides longifoveatus sp.nov.is characterized by its papilliform cephalic sensilla;long and narrow amphideal fovea with fine transverse striations;inverse S-shaped spicules with a dorsally bent manubrium;gubernaculum with dorso-caudal apophysis;cylindrical tail with round terminal end.Minolaimus multisupplementatus sp.nov.is characterized by cuticle with lateral differentiation of three longitudinal rows of large dots,spiral amphideal fovea with seven turns,pharynx cylindrical without posterior bulb,spicules arcuated with central lamella,gubernaculum arcuate and parallel to spicule,without dorso-caudal apophysis,a papilliform and 29 cup-shaped precloacal supplement;tail conical with long flagelliform portion.Minolaimus apicalis sp.nov.is characterized by cuticle with lateral differentiation of three longitudinal rows of larger dots from the middle of pharynx to the conical portion of tail and a longitudinal row of pores in the pharyngeal region and precloacal region;spiral amphidial fovea with four turns and close to anterior end;pharynx cylindrical with oval posterior bulb,spicules arcuated and proximal end bent dorsally,gubernaculum with a broad curved dorsal apophysis;two sucked-like and six cup-shaped cuticularized precloacal supplements;tail conico-cylindrical with slightly enlarged tip.Updated keys to species of Diplopeltoides and Minolaimus were provided.
基金supported by Shanghai Young Talent Development Program and Innovative Research Team of Shanghai University of Finance and Economics(Grant No.2020110930)supported by the Department of Energy of USA(Grant No.DE-EE0008574)。
文摘In this paper, we propose a new estimation method for a nonparametric hidden Markov model(HMM), in which both the emission model and the transition matrix are nonparametric, and a semiparametric HMM, in which the transition matrix is parametric while emission models are nonparametric. The estimation is based on a novel composite likelihood method, where the pairs of consecutive observations are treated as independent bivariate random variables. Therefore, the model is transformed into a mixture model, and a modified expectation-maximization(EM) algorithm is developed to compute the maximum composite likelihood.We systematically study asymptotic properties for both the nonparametric HMM and the semiparametric HMM. We also propose a generalized likelihood ratio test to choose between the nonparametric HMM and the semiparametric HMM. We derive the asymptotic distribution and prove the Wilk’s phenomenon of the proposed test statistics. Simulation studies and an application in volatility clustering analysis of the volatility index in the Chicago Board Options Exchange(CBOE) are conducted to demonstrate the effectiveness of the proposed methods.
基金the National Natural Science Foundation of China(No.71773009)the Key Program of the National Social Science Fund of China(No.21AZD028).
文摘Based on a representative survey of new college graduates in China,we present a job location choice model that allows for a self-selection effect in college regions by considering region-dependent heterogeneous preference for job locations and unobservable location features.We also treat endogenous housing costs using the method developed by Berry et al.(1995).Our estimation results show that college education significantly increases graduates'likelihood of working in the city where their college is located.However,a model that does not consider the self-selection effect overestimates this impact.The impact of college location on a graduate's migration decision varies considerably across cities.There is significant heterogeneity between students from universities of dijferent tiers and rural versus urban areas.Meanwhile,the graduates show a marked home preference when choosing their job locations,and they tend to avoid working in cities with high housing costs.These findings shed light on debates on place-based higher education policies and spatial distribution of human capital with a high level of education.
