To address the current limitations of time-gated Raman spectroscopy,specifically its narrow spectral range and low spectral resolution,and simultaneously acquire Raman and fluorescence life-time images,we have develop...To address the current limitations of time-gated Raman spectroscopy,specifically its narrow spectral range and low spectral resolution,and simultaneously acquire Raman and fluorescence life-time images,we have developed a Fourier-transform photon counting spectroscopy platform.A Mach-Zehnder interferometer employing a high accuracy linear motor stage was combined with photon-counting avalanche diodes and time-tagged acquisition,allowing to sort photons into a matrix of stage positions determined using their coarse arrival time with 50 ns steps of the excitation laser repetition period,and a fine arrival time of 80 ps resolution relative to the excitation pulse of 100 ps duration.The instrument achieves a time resolution of 547 ps,a wide spectral range of−1000 to 10,000 cm−1 Raman shift from the excitation at 532 nm wavelength,and a high spectral resolution of 0.05 cm−1.For experimental validation,we used fluorescently coated silicon wafers and fluorescent plastic microspheres.Raman signal was observed during the laser excitation pulse within the time-resolution,while fluorescence signals dominate afterwards.The results confirm that the instrument can effectively separate Raman and fluorescence signals.展开更多
In the area of time series modelling, several applications are encountered in real-life that involve analysis of count time series data. The distribution characteristics and dependence structure are the major issues t...In the area of time series modelling, several applications are encountered in real-life that involve analysis of count time series data. The distribution characteristics and dependence structure are the major issues that arise while specifying a modelling strategy to handle the analysis of those kinds of data. Owing to the numerous applications there is a need to develop models that can capture these features. However, accounting for both aspects simultaneously presents complexities while specifying a modeling strategy. In this paper, an alternative statistical model able to deal with issues of discreteness, overdispersion, serial correlation over time is proposed. In particular, we adopt a branching mechanism to develop a first-order stationary negative binomial autoregressive model. Inference is based on maximum likelihood estimation and a simulation study is conducted to evaluate the performance of the proposed approach. As an illustration, the model is applied to a real-life dataset in crime analysis.展开更多
Fluorescence lifetime imaging microscopy(FLIM)is a powerful tool to discriminate fluorescent molecules or probe their nanoscale environment.Traditionally,FLIM uses time-correlated single-photon counting(TCSPC),which i...Fluorescence lifetime imaging microscopy(FLIM)is a powerful tool to discriminate fluorescent molecules or probe their nanoscale environment.Traditionally,FLIM uses time-correlated single-photon counting(TCSPC),which is precise but intrinsically low-throughput due to its dependence on point detectors.Although time-gated cameras have demonstrated the potential for high-throughput FLIM in bright samples with dense labeling,their use in single-molecule microscopy has not been explored extensively.Here,we report fast and accurate single-molecule FLIM with a commercial time-gated single-photon camera.Our optimized acquisition scheme achieves single-molecule lifetime measurements with a precision only about three times less than TCSPC,while imaging with a large number of pixels(512×512)allowing for the spatial multiplexing of over 3000 molecules.With this approach,we demonstrate parallelized lifetime measurements of large numbers of labeled pore-forming proteins on supported lipid bilayers,and temporal single-molecule Förster resonance energy transfer measurements at 5-25 Hz.This method holds considerable promise for the advancement of multi-target single-molecule localization microscopy and biopolymer sequencing.展开更多
In the measurement of fluorescent lifetime based on time correlation-single photon counting technique by means of TAC, due to the contamination of multi-photons a deviation of fluorescent lifetime measured from the ex...In the measurement of fluorescent lifetime based on time correlation-single photon counting technique by means of TAC, due to the contamination of multi-photons a deviation of fluorescent lifetime measured from the expected value is experimentally studied. A correction function instead of a simple exponential function is used to fit the experiment data. The validation of the correction function is checked using the experimental data of several test samples： YAP, NaI（T1） and LSO. The results show that the correction function well fits the data and the reasonable fluorescent lifetimes are obtained.展开更多
To better capture the characteristics of asymmetry and structural fluctuations observed in count time series,this study delves into the application of the quantile regression(QR)method for analyzing and forecasting no...To better capture the characteristics of asymmetry and structural fluctuations observed in count time series,this study delves into the application of the quantile regression(QR)method for analyzing and forecasting nonlinear integer-valued time series exhibiting a piecewise phenomenon.Specifically,we focus on the parameter estimation in the first-order Self-Exciting Threshold Integer-valued Autoregressive(SETINAR(2,1))process with symmetry,asymmetry,and contaminated innovations.We establish the asymptotic properties of the estimator under certain regularity conditions.Monte Carlo simulations demonstrate the superior performance of the QR method compared to the conditional least squares(CLS)approach.Furthermore,we validate the robustness of the proposed method through empirical quantile regression estimation and forecasting for larceny incidents and CAD drug call counts in Pittsburgh,showcasing its effectiveness across diverse levels of data heterogeneity.展开更多
The Poisson integer-valued GARCH model is a popular tool in modeling time series of counts.The commonly used maximum likelihood estimator is strongly influenced by outliers,so there is a need to develop a robust M-est...The Poisson integer-valued GARCH model is a popular tool in modeling time series of counts.The commonly used maximum likelihood estimator is strongly influenced by outliers,so there is a need to develop a robust M-estimator for this model.This paper has three aims.First,the authors propose a new loss function,which is a hybrid of the tri-weight loss for relatively small errors and the exponential squared loss for relatively large ones.Second,Mallows’quasi-likelihood estimator(MQLE)is proposed as an M-estimator and its existence,uniqueness,consistency and asymptotic normality are established.In addition,a data-adaptive algorithm for computing MQLE is given based on a datadriven selection of tuning parameters in the loss function.Third,simulation studies and analysis of a real example are conducted to illustrate the performance of the new estimator,and a comparison with existing estimators is made.展开更多
This paper discusses our collaboration work with government officers in the health department of Seoul during the COVID-19 pandemic.First,we focus on short-term forecasting for the number of new confirmed cases and se...This paper discusses our collaboration work with government officers in the health department of Seoul during the COVID-19 pandemic.First,we focus on short-term forecasting for the number of new confirmed cases and severe cases.Second,we focus on understanding how much of the current infections has been affected by external influx from neighborhood areas or internal transmission within the area.This understanding may be important because it is linked to the government policy determining nonpharmaceutical interventions.To obtain the decomposition of the effect,districts of Seoul should be considered simultaneously,and multivariate time series models are used.Third,we focus on predicting the number of new weekly confirmed cases for each district in Seoul.This detailed prediction may be important to the government policy on resource allocation.We consider an ensemble method to overcome poor prediction performance of simple models.This paper presents the methodological details and analysis results of the study.展开更多
基金Funded by Chinese Academy of Sciences President’s International Fellowship Initiative.Grant No.2022VBA0028.
文摘To address the current limitations of time-gated Raman spectroscopy,specifically its narrow spectral range and low spectral resolution,and simultaneously acquire Raman and fluorescence life-time images,we have developed a Fourier-transform photon counting spectroscopy platform.A Mach-Zehnder interferometer employing a high accuracy linear motor stage was combined with photon-counting avalanche diodes and time-tagged acquisition,allowing to sort photons into a matrix of stage positions determined using their coarse arrival time with 50 ns steps of the excitation laser repetition period,and a fine arrival time of 80 ps resolution relative to the excitation pulse of 100 ps duration.The instrument achieves a time resolution of 547 ps,a wide spectral range of−1000 to 10,000 cm−1 Raman shift from the excitation at 532 nm wavelength,and a high spectral resolution of 0.05 cm−1.For experimental validation,we used fluorescently coated silicon wafers and fluorescent plastic microspheres.Raman signal was observed during the laser excitation pulse within the time-resolution,while fluorescence signals dominate afterwards.The results confirm that the instrument can effectively separate Raman and fluorescence signals.
文摘In the area of time series modelling, several applications are encountered in real-life that involve analysis of count time series data. The distribution characteristics and dependence structure are the major issues that arise while specifying a modelling strategy to handle the analysis of those kinds of data. Owing to the numerous applications there is a need to develop models that can capture these features. However, accounting for both aspects simultaneously presents complexities while specifying a modeling strategy. In this paper, an alternative statistical model able to deal with issues of discreteness, overdispersion, serial correlation over time is proposed. In particular, we adopt a branching mechanism to develop a first-order stationary negative binomial autoregressive model. Inference is based on maximum likelihood estimation and a simulation study is conducted to evaluate the performance of the proposed approach. As an illustration, the model is applied to a real-life dataset in crime analysis.
基金support from the EPFL Center for Imaging(A.R.,N.R.,E.C.and C.B.)European Research Council(grant 101020445 to A.R.)+2 种基金the Swiss National Science Foundation(grant 200021-184687 to G.P.A.,grant 200021L-212128 to M.D.P.and grant IZSEZ0-224299 to R.R.)the National Center of Competence in Research Bio-Inspired Materials(NCCR 51NF40-182881 to G.P.A.and A.R.)the European Union Program HORIZON-Pathfinder-Open(grant 101099125 to G.P.A.).
文摘Fluorescence lifetime imaging microscopy(FLIM)is a powerful tool to discriminate fluorescent molecules or probe their nanoscale environment.Traditionally,FLIM uses time-correlated single-photon counting(TCSPC),which is precise but intrinsically low-throughput due to its dependence on point detectors.Although time-gated cameras have demonstrated the potential for high-throughput FLIM in bright samples with dense labeling,their use in single-molecule microscopy has not been explored extensively.Here,we report fast and accurate single-molecule FLIM with a commercial time-gated single-photon camera.Our optimized acquisition scheme achieves single-molecule lifetime measurements with a precision only about three times less than TCSPC,while imaging with a large number of pixels(512×512)allowing for the spatial multiplexing of over 3000 molecules.With this approach,we demonstrate parallelized lifetime measurements of large numbers of labeled pore-forming proteins on supported lipid bilayers,and temporal single-molecule Förster resonance energy transfer measurements at 5-25 Hz.This method holds considerable promise for the advancement of multi-target single-molecule localization microscopy and biopolymer sequencing.
文摘In the measurement of fluorescent lifetime based on time correlation-single photon counting technique by means of TAC, due to the contamination of multi-photons a deviation of fluorescent lifetime measured from the expected value is experimentally studied. A correction function instead of a simple exponential function is used to fit the experiment data. The validation of the correction function is checked using the experimental data of several test samples： YAP, NaI（T1） and LSO. The results show that the correction function well fits the data and the reasonable fluorescent lifetimes are obtained.
基金supported by Social Science Planning Foundation of Liaoning Province(Grand No.L22ZD065)National Natural Science Foundation of China(Grand Nos.12271231,1247012719,12001229)。
文摘To better capture the characteristics of asymmetry and structural fluctuations observed in count time series,this study delves into the application of the quantile regression(QR)method for analyzing and forecasting nonlinear integer-valued time series exhibiting a piecewise phenomenon.Specifically,we focus on the parameter estimation in the first-order Self-Exciting Threshold Integer-valued Autoregressive(SETINAR(2,1))process with symmetry,asymmetry,and contaminated innovations.We establish the asymptotic properties of the estimator under certain regularity conditions.Monte Carlo simulations demonstrate the superior performance of the QR method compared to the conditional least squares(CLS)approach.Furthermore,we validate the robustness of the proposed method through empirical quantile regression estimation and forecasting for larceny incidents and CAD drug call counts in Pittsburgh,showcasing its effectiveness across diverse levels of data heterogeneity.
基金supported by Research Start-up Fund of Changchun Normal UniversityNatural Science Found of Changchun Normal University under Grant No.2018-004+1 种基金the National Natural Science Foundation of China under Grant Nos.11871027 and 11731015Cultivation Plan for Excellent Young Scholar Candidates of Jilin University。
文摘The Poisson integer-valued GARCH model is a popular tool in modeling time series of counts.The commonly used maximum likelihood estimator is strongly influenced by outliers,so there is a need to develop a robust M-estimator for this model.This paper has three aims.First,the authors propose a new loss function,which is a hybrid of the tri-weight loss for relatively small errors and the exponential squared loss for relatively large ones.Second,Mallows’quasi-likelihood estimator(MQLE)is proposed as an M-estimator and its existence,uniqueness,consistency and asymptotic normality are established.In addition,a data-adaptive algorithm for computing MQLE is given based on a datadriven selection of tuning parameters in the loss function.Third,simulation studies and analysis of a real example are conducted to illustrate the performance of the new estimator,and a comparison with existing estimators is made.
基金This studywas exempted from review by the Institutional ReviewBoard(IRB)of Seoul National University(SNU IRB no.21-08-109)because the data were aggregated and anonymizedThis work was supported by the National Research Foundation of Korea(BK21 Center for Integrative Response to Health Disasters,Graduate School of Public Health,Seoul National University)(NO.4199990514025)Woojoo Lee was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(no.2021R1A2C1014409).
文摘This paper discusses our collaboration work with government officers in the health department of Seoul during the COVID-19 pandemic.First,we focus on short-term forecasting for the number of new confirmed cases and severe cases.Second,we focus on understanding how much of the current infections has been affected by external influx from neighborhood areas or internal transmission within the area.This understanding may be important because it is linked to the government policy determining nonpharmaceutical interventions.To obtain the decomposition of the effect,districts of Seoul should be considered simultaneously,and multivariate time series models are used.Third,we focus on predicting the number of new weekly confirmed cases for each district in Seoul.This detailed prediction may be important to the government policy on resource allocation.We consider an ensemble method to overcome poor prediction performance of simple models.This paper presents the methodological details and analysis results of the study.
