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1.
PLoS One ; 15(10): e0239371, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33001996

RESUMO

Mastering the evolution of urban land cover is important for urban management and planning. In this paper, a method for analyzing land cover evolution within urban built-up areas based on nighttime light data and Landsat data is proposed. The method solves the problem of inaccurate descriptions of urban built-up area boundaries from the use of single-source diurnal or nocturnal remote sensing data and was able to achieve an effective analysis of land cover evolution within built-up areas. Four main procedures are involved: (1) The neighborhood extremum method and maximum likelihood method are used to extract nighttime light data and the urban built-up area boundaries from the Landsat data, respectively; (2) multisource urban boundaries are obtained using boundary pixel fusion of the nighttime light data and Landsat urban built-up area boundaries; (3) the maximum likelihood method is used to classify Landsat data within multisource urban boundaries into land cover classes, such as impervious surface, vegetation and water, and to calculate landscape indexes, such as overall landscape trends, degree of fragmentation and degree of aggregation; (4) the changes in the multisource urban boundaries and landscape indexes were obtained using the abovementioned methods, which were supported by multitemporal nighttime light data and Landsat data, to model the urban land cover evolution. Using the cities of Shenyang, Changchun and Harbin in northeastern China as experimental areas, the multitemporal landscape index showed that the integration and aggregation of land cover in the urban areas had an increasing trend, the natural environment of Shenyang and Harbin was improving, while Changchun laid more emphasis on the construction of artificial facilities. At the same time, the method proposed in this paper to extract built-up areas from multi-source city data showed that the user accuracy, production accuracy, overall accuracy and Kappa coefficient are at least 3%, 1%, 1% and 0.04 higher than the single-source data method.


Assuntos
Monitoramento Ambiental , Luz , Urbanização , China , Planejamento de Cidades , Funções Verossimilhança
2.
Epidemiol Infect ; 148: e257, 2020 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-33092672

RESUMO

The outbreak of the novel coronavirus severe acute respiratory syndrome-coronavirus-2 has raised major health policy questions and dilemmas. Whilst respiratory droplets are believed to be the dominant transmission mechanisms, indirect transmission may also occur through shared contact of contaminated common objects that is not directly curtailed by a lockdown. The conditions under which contaminated common objects may lead to significant spread of coronavirus disease 2019 during lockdown and its easing is examined using the susceptible-exposed-infectious-removed model with a fomite term added. Modelling the weekly death rate in the UK, a maximum-likelihood analysis finds a statistically significant fomite contribution, with 0.009 ± 0.001 (95% CI) infection-inducing fomites introduced into the environment per day per infectious person. Post-lockdown, comparison with the prediction of a corresponding counterfactual model with no fomite transmission suggests fomites, through enhancing the overall transmission rate, may have contributed to as much as 25% of the deaths following lockdown. It is suggested that adding a fomite term to more complex simulations may assist in the understanding of the spread of the illness and in making policy decisions to control it.


Assuntos
Betacoronavirus , Infecções por Coronavirus/mortalidade , Infecções por Coronavirus/transmissão , Fômites/virologia , Pneumonia Viral/mortalidade , Pneumonia Viral/transmissão , Fatores Etários , Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/prevenção & controle , Política de Saúde/tendências , Humanos , Incidência , Funções Verossimilhança , Modelos Teóricos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Serviços Postais/estatística & dados numéricos , Reino Unido/epidemiologia
3.
PLoS One ; 15(10): e0238746, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33002015

RESUMO

The paper investigates a new scheme for generating lifetime probability distributions. The scheme is called Exponential- H family of distribution. The paper presents an application of this family by using the Weibull distribution, the new distribution is then called New Flexible Exponential distribution or in short NFE. Various statistical properties are derived, such as quantile function, order statistics, moments, etc. Two real-life data sets and a simulation study have been performed so that to assure the flexibility of the proposed model. It has been declared that the proposed distribution offers nice results than Exponential, Weibull Exponential, and Exponentiated Exponential distribution.


Assuntos
Teoria da Probabilidade , Distribuições Estatísticas , Acidentes de Trânsito/estatística & dados numéricos , Aeronaves , Simulação por Computador , Análise de Falha de Equipamento/estatística & dados numéricos , Humanos , Tábuas de Vida , Funções Verossimilhança , Modelos Estatísticos , Modelos de Riscos Proporcionais
4.
BMC Infect Dis ; 20(1): 772, 2020 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-33076868

RESUMO

BACKGROUND: CRF_BC recombinants, including CRF07_BC and CRF08_BC, were considered the predominant subtypes in China. Since the discovery of HIV-1 circulating recombinant form CRF 85_BC in Southwest China in 2016, this BC recombinant forms had been reported in different regions of China. However, the history and magnitude of CRF85_BC transmission were still to be investigated. METHOD: We conducted the most recent molecular epidemiology of HIV-1 among newly reported HIV-1 infected patients in Sichuan in 2019 by sequencing and phylogenetic analysis of 1291 pol sequences. Then, we used maximum likelihood approach and the Bayesian Markov chain Monte Carlo (MCMC) sampling of pol sequences to reconstruct the phylogeographic and demographic dynamics of the CRF85_BC. RESULTS: HIV-1 CRF85_BC (68/1291, 5.27%) became the fourth most prevalent strain revealing a significant increase in local population. CRF85_BC were only found in heterosexually infected individuals and the majority of CRF85_BC (95.45%) were circulating among the people living with HIV aged 50 years and over (PLHIV50+), suggesting a unique prevalent pattern. The founder lineages of CRF85_BC were likely to have first emerged in Yunnan, a province of Southwest China bordering Sichuan, in the early 2000s. It then spread exponentially to various places (including Guangxi, Sichuan, et al) and became endemic around 2008.6 (2006.7-2010.2) in Sichuan. CONCLUSION: Taken together, our findings on HIV-1 subtype CRF85_BC infections provided new insights into the spread of this virus and extended the understanding of the HIV epidemic in China.


Assuntos
Infecções por HIV/transmissão , Infecções por HIV/virologia , HIV-1/classificação , Adulto , Teorema de Bayes , China/epidemiologia , Epidemias , Feminino , Genótipo , Infecções por HIV/epidemiologia , HIV-1/genética , HIV-1/isolamento & purificação , Heterossexualidade , Humanos , Funções Verossimilhança , Masculino , Pessoa de Meia-Idade , Epidemiologia Molecular , Filogenia , Filogeografia
5.
Science ; 370(6516): 571-575, 2020 10 30.
Artigo em Inglês | MEDLINE | ID: mdl-32913002

RESUMO

After its emergence in Wuhan, China, in late November or early December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus rapidly spread globally. Genome sequencing of SARS-CoV-2 allows the reconstruction of its transmission history, although this is contingent on sampling. We analyzed 453 SARS-CoV-2 genomes collected between 20 February and 15 March 2020 from infected patients in Washington state in the United States. We find that most SARS-CoV-2 infections sampled during this time derive from a single introduction in late January or early February 2020, which subsequently spread locally before active community surveillance was implemented.


Assuntos
Betacoronavirus/genética , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/transmissão , Genoma Viral , Pneumonia Viral/epidemiologia , Pneumonia Viral/transmissão , Teorema de Bayes , Humanos , Funções Verossimilhança , Pandemias , Filogenia , Washington/epidemiologia
6.
PLoS One ; 15(9): e0239003, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32915903

RESUMO

This research mainly aims to develop a generalized cure rate model, estimate the proportion of cured patients and their survival rate, and identify the risk factors associated with infectious diseases. The generalized cure rate model is based on bounded cumulative hazard function, which is a non-mixture model, and is developed using a two-parameter Weibull distribution as the baseline distribution, to estimate the cure rate using maximum likelihood method and real data with R and STATA software. The results showed that the cure rate of tuberculosis (TB) patients was 26.3%, which was higher than that of TB patients coinfected with human immunodeficiency virus (HIV; 23.1%). The non-parametric median survival time of TB patients was 51 months, while that of TB patients co-infected with HIV was 33 months. Moreover, no risk factors were associated with TB patients co-infected with HIV, while age was a significant risk factor for TB patients among the suspected risk factors considered. Furthermore, the bounded cumulative hazard function was extended to accommodate infectious diseases with co-infections by deriving an appropriate probability density function, determining the distribution, and using real data. Governments and related health authorities are also encouraged to take appropriate actions to combat infectious diseases with possible co-infections.


Assuntos
Doenças Transmissíveis/terapia , Modelos Biológicos , Coinfecção/mortalidade , Coinfecção/terapia , Controle de Doenças Transmissíveis , Doenças Transmissíveis/mortalidade , Feminino , Infecções por HIV/complicações , Infecções por HIV/mortalidade , Infecções por HIV/terapia , Humanos , Estimativa de Kaplan-Meier , Funções Verossimilhança , Masculino , Nigéria/epidemiologia , Modelos de Riscos Proporcionais , Fatores de Risco , Estatísticas não Paramétricas , Tuberculose Pulmonar/complicações , Tuberculose Pulmonar/mortalidade , Tuberculose Pulmonar/terapia
7.
Math Biosci Eng ; 17(4): 3512-3519, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32987541

RESUMO

The coronavirus disease 2019 (COVID-19) emerged in Wuhan, China in the end of 2019, and soon became a serious public health threat globally. Due to the unobservability, the time interval between transmission generations (TG), though important for understanding the disease transmission patterns, of COVID-19 cannot be directly summarized from surveillance data. In this study, we develop a likelihood framework to estimate the TG and the pre-symptomatic transmission period from the serial interval observations from the individual transmission events. As the results, we estimate the mean of TG at 4.0 days (95%CI: 3.3-4.6), and the mean of pre-symptomatic transmission period at 2.2 days (95%CI: 1.3-4.7). We approximate the mean latent period of 3.3 days, and 32.2% (95%CI: 10.3-73.7) of the secondary infections may be due to pre-symptomatic transmission. The timely and effectively isolation of symptomatic COVID-19 cases is crucial for mitigating the epidemics.


Assuntos
Betacoronavirus , Infecções por Coronavirus/transmissão , Pandemias , Pneumonia Viral/transmissão , Número Básico de Reprodução/estatística & dados numéricos , China/epidemiologia , Infecções por Coronavirus/epidemiologia , Humanos , Funções Verossimilhança , Conceitos Matemáticos , Modelos Biológicos , Pandemias/estatística & dados numéricos , Pneumonia Viral/epidemiologia , Fatores de Tempo
8.
PLoS One ; 15(8): e0237462, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853259

RESUMO

In the present study, a new class of heavy tailed distributions using the T-X family approach is introduced. The proposed family is called type-I heavy tailed family. A special model of the proposed class, named Type-I Heavy Tailed Weibull (TI-HTW) model is studied in detail. We adopt the approach of maximum likelihood estimation for estimating its parameters, and assess the maximum likelihood performance based on biases and mean squared errors via a Monte Carlo simulation framework. Actuarial quantities such as value at risk and tail value at risk are derived. A simulation study for these actuarial measures is conducted, proving that the proposed TI-HTW is a heavy-tailed model. Finally, we provide a comparative study to illustrate the proposed method by analyzing three real data sets from different disciplines such as reliability engineering, bio-medical and financial sciences. The analytical results of the new TI-HTW model are compared with the Weibull and some other non-nested distributions. The Baysesian analysis is discussed to measure the model complexity based on the deviance information criterion.


Assuntos
Modelos Estatísticos , Economia , Engenharia , Funções Verossimilhança , Método de Monte Carlo , Farmacologia , Projetos de Pesquisa
9.
Nat Commun ; 11(1): 4031, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32788582

RESUMO

Calcium (Ca2+) influx into mitochondria occurs through a Ca2+-selective uniporter channel, which regulates essential cellular processes in eukaryotic organisms. Previous evolutionary analyses of its pore-forming subunits MCU and EMRE, and gatekeeper MICU1, pinpointed an evolutionary paradox: the presence of MCU homologs in fungal species devoid of any other uniporter components and of mt-Ca2+ uptake. Here, we trace the mt-Ca2+ uniporter evolution across 1,156 fully-sequenced eukaryotes and show that animal and fungal MCUs represent two distinct paralogous subfamilies originating from an ancestral duplication. Accordingly, we find EMRE orthologs outside Holoza and uncover the existence of an animal-like uniporter within chytrid fungi, which enables mt-Ca2+ uptake when reconstituted in vivo in the yeast Saccharomyces cerevisiae. Our study represents the most comprehensive phylogenomic analysis of the mt-Ca2+ uptake system and demonstrates that MCU, EMRE, and MICU formed the core of the ancestral opisthokont uniporter, with major implications for comparative structural and functional studies.


Assuntos
Canais de Cálcio/genética , Evolução Molecular , Proteínas Fúngicas/genética , Sequência de Aminoácidos , Cálcio/metabolismo , Canais de Cálcio/química , Quitridiomicetos/genética , Proteínas Fúngicas/química , Células HeLa , Humanos , Funções Verossimilhança , Filogenia , Especificidade da Espécie
10.
PLoS Comput Biol ; 16(8): e1008065, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32797037

RESUMO

Inference of admixture proportions is a classical statistical problem in population genetics. Standard methods implicitly assume that both parents of an individual have the same admixture fraction. However, this is rarely the case in real data. In this paper we show that the distribution of admixture tract lengths in a genome contains information about the admixture proportions of the ancestors of an individual. We develop a Hidden Markov Model (HMM) framework for estimating the admixture proportions of the immediate ancestors of an individual, i.e. a type of decomposition of an individual's admixture proportions into further subsets of ancestral proportions in the ancestors. Based on a genealogical model for admixture tracts, we develop an efficient algorithm for computing the sampling probability of the genome from a single individual, as a function of the admixture proportions of the ancestors of this individual. This allows us to perform probabilistic inference of admixture proportions of ancestors only using the genome of an extant individual. We perform extensive simulations to quantify the error in the estimation of ancestral admixture proportions under various conditions. To illustrate the utility of the method, we apply it to real genetic data.


Assuntos
Genética Populacional/métodos , Avós , Pais , Linhagem , Bases de Dados Genéticas , Humanos , Funções Verossimilhança , Cadeias de Markov
11.
Nat Commun ; 11(1): 3861, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32737316

RESUMO

Integrating results from genome-wide association studies (GWASs) and gene expression studies through transcriptome-wide association study (TWAS) has the potential to shed light on the causal molecular mechanisms underlying disease etiology. Here, we present a probabilistic Mendelian randomization (MR) method, PMR-Egger, for TWAS applications. PMR-Egger relies on a MR likelihood framework that unifies many existing TWAS and MR methods, accommodates multiple correlated instruments, tests the causal effect of gene on trait in the presence of horizontal pleiotropy, and is scalable to hundreds of thousands of individuals. In simulations, PMR-Egger provides calibrated type I error control for causal effect testing in the presence of horizontal pleiotropic effects, is reasonably robust under various types of model misspecifications, is more powerful than existing TWAS/MR approaches, and can directly test for horizontal pleiotropy. We illustrate the benefits of PMR-Egger in applications to 39 diseases and complex traits obtained from three GWASs including the UK Biobank.


Assuntos
Pleiotropia Genética , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla/estatística & dados numéricos , Análise da Randomização Mendeliana/estatística & dados numéricos , Modelos Genéticos , Transcriptoma , Doenças Cardiovasculares/diagnóstico , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/patologia , Simulação por Computador , Bases de Dados Factuais , Gastroenteropatias/diagnóstico , Gastroenteropatias/genética , Gastroenteropatias/patologia , Humanos , Doenças do Sistema Imunitário/diagnóstico , Doenças do Sistema Imunitário/genética , Doenças do Sistema Imunitário/patologia , Funções Verossimilhança , Doenças Metabólicas/diagnóstico , Doenças Metabólicas/genética , Doenças Metabólicas/patologia , Herança Multifatorial , Neoplasias/diagnóstico , Neoplasias/genética , Neoplasias/patologia , Doenças Neurodegenerativas/diagnóstico , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/patologia
12.
Epidemiol Infect ; 148: e166, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32753078

RESUMO

Following the importation of coronavirus disease (COVID-19) into Nigeria on 27 February 2020 and then the outbreak, the question is: How do we anticipate the progression of the ongoing epidemic following all the intervention measures put in place? This kind of question is appropriate for public health responses and it will depend on the early estimates of the key epidemiological parameters of the virus in a defined population.In this study, we combined a likelihood-based method using a Bayesian framework and compartmental model of the epidemic of COVID-19 in Nigeria to estimate the effective reproduction number (R(t)) and basic reproduction number (R0) - this also enables us to estimate the initial daily transmission rate (ß0). We further estimate the reported fraction of symptomatic cases. The models are applied to the NCDC data on COVID-19 symptomatic and death cases from 27 February 2020 and 7 May 2020.In this period, the effective reproduction number is estimated with a minimum value of 0.18 and a maximum value of 2.29. Most importantly, the R(t) is strictly greater than one from 13 April till 7 May 2020. The R0 is estimated to be 2.42 with credible interval: (2.37-2.47). Comparing this with the R(t) shows that control measures are working but not effective enough to keep R(t) below 1. Also, the estimated fraction of reported symptomatic cases is between 10 and 50%.Our analysis has shown evidence that the existing control measures are not enough to end the epidemic and more stringent measures are needed.


Assuntos
Número Básico de Reprodução/estatística & dados numéricos , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Epidemias/prevenção & controle , Pandemias/prevenção & controle , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Prática de Saúde Pública , Teorema de Bayes , Humanos , Funções Verossimilhança , Nigéria/epidemiologia
13.
Zhonghua Liu Xing Bing Xue Za Zhi ; 41(7): 1000-1003, 2020 Jul 10.
Artigo em Chinês | MEDLINE | ID: mdl-32741161

RESUMO

Objectives: The COVID-19 has been the public health issues of global concern, but the incubation period was still under discussion. This study aimed to estimate the incubation period distribution of COVID-19. Methods: The exposure and onset information of COVID-19 cases were collected from the official information platform of provincial or municipal health commissions. The distribution of COVID-19 incubation period was estimated based on the Log- normal, Gamma and Weibull distribution by interval-censored data estimation method. Results: A total of 109 confirmed cases were collected, with an average age of 39.825 years. The median COVID-19 incubation period based on Log-normal, Gamma, and Weibull distribution were 4.958 (P(25)-P(75): 3.472-7.318) days, 5.083 (P(25)-P(75): 3.511-7.314) days, and 5.695 (P(25)-P(75): 3.675-7.674) days, respectively. Gamma distribution had the largest log-likelihood result. Conclusions: The distribution of COVID-19 incubation period followed the Gamma distribution, and the interval-censored data estimation method can be used to estimate the incubation period distribution.


Assuntos
Infecções por Coronavirus/epidemiologia , Período de Incubação de Doenças Infecciosas , Pneumonia Viral/epidemiologia , Adulto , Humanos , Funções Verossimilhança , Pandemias
14.
PLoS One ; 15(8): e0237832, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32841283

RESUMO

This paper analyses the evolution of COVID-19 in Cameroon over the period March 6-April 2020 using SIR models. Specifically, we 1) evaluate the basic reproduction number of the virus, 2) determine the peak of the infection and the spread-out period of the disease, and 3) simulate the interventions of public health authorities. Data used in this study is obtained from the Cameroonian Public Health Ministry. The results suggest that over the identified period, the reproduction number of COVID-19 in Cameroon is about 1.5, and the peak of the infection should have occurred at the end of May 2020 with about 7.7% of the population infected. Furthermore, the implementation of efficient public health policies could help flatten the epidemic curve.


Assuntos
Número Básico de Reprodução , Infecções por Coronavirus/epidemiologia , Progressão da Doença , Pneumonia Viral/epidemiologia , Algoritmos , Betacoronavirus , Camarões/epidemiologia , Simulação por Computador , Infecções por Coronavirus/prevenção & controle , Humanos , Funções Verossimilhança , Modelos Estatísticos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle
16.
PLoS One ; 15(8): e0232030, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32745104

RESUMO

The Interpersonal Needs Questionnaire (INQ) assesses Thwarted Belongingness (TB) and Perceived Burdensomeness (PB), two predictors of suicidal thoughts. Up to now, the use of item response theory (IRT) for the evaluation of the INQ has been restricted to a single study with clinically depressed and suicidal youth. Therefore, the psychometric properties of the two INQ-15-subscales TB and PB were now evaluated in a general population sample (N = 2508) and a clinical adult population sample (N = 185) using IRT, specifically the Rasch model (RM) and the graphical log-linear Rasch model (GLLRM). Of special interest was whether the INQ-subscales displayed differential item functioning (DIF) across the two different samples and how well the subscales were targeted to the two sample populations. For the clinical sample, fit to a GLLRM could be established for the PB-subscale and fit to a RM was established for a five-item version of the TB-subscale. In contrast, for the general population sample fit to a GLLRM could only be achieved for the PB-subscale. Overall, there was strong evidence of local dependence (LD) across items and of some age- and gender-related DIF. Both subscales exhibited massive DIF related to the sample, indicating that they don't work the same across the general population and clinical sample. As expected, targeting of both INQ-subscales was much better for the clinical population. Further investigations of the INQ-15 under the Rasch approach in a large clinical population are recommended to determine and optimize the scale performance.


Assuntos
Psicometria/métodos , Ideação Suicida , Suicídio , Inquéritos e Questionários , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Alemanha , Humanos , Funções Verossimilhança , Masculino , Pessoa de Meia-Idade , Modelos Psicológicos , Modelos Estatísticos , Suicídio/psicologia , Suicídio/estatística & dados numéricos , Inquéritos e Questionários/estatística & dados numéricos , Adulto Jovem
17.
PLoS One ; 15(8): e0236954, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760106

RESUMO

To infer the parameters of mechanistic models with intractable likelihoods, techniques such as approximate Bayesian computation (ABC) are increasingly being adopted. One of the main disadvantages of ABC in practical situations, however, is that parameter inference must generally rely on summary statistics of the data. This is particularly the case for problems involving high-dimensional data, such as biological imaging experiments. However, some summary statistics contain more information about parameters of interest than others, and it is not always clear how to weight their contributions within the ABC framework. We address this problem by developing an automatic, adaptive algorithm that chooses weights for each summary statistic. Our algorithm aims to maximize the distance between the prior and the approximate posterior by automatically adapting the weights within the ABC distance function. Computationally, we use a nearest neighbour estimator of the distance between distributions. We justify the algorithm theoretically based on properties of the nearest neighbour distance estimator. To demonstrate the effectiveness of our algorithm, we apply it to a variety of test problems, including several stochastic models of biochemical reaction networks, and a spatial model of diffusion, and compare our results with existing algorithms.


Assuntos
Algoritmos , Teorema de Bayes , Biometria/métodos , Fenômenos Bioquímicos , Simulação por Computador , Funções Verossimilhança , Cadeias de Markov , Redes e Vias Metabólicas , Modelos Biológicos , Modelos Estatísticos , Método de Monte Carlo , Análise de Regressão , Processos Estocásticos
18.
PLoS One ; 15(8): e0236979, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760110

RESUMO

The aim of this study is to identify the dynamic explicit and implicit information factors which displayed on the webpage of platforms that influence backers' investment decision-making behavior. We analyze the connections among these factors by collecting the longitudinal dataset from reward-based crowdfunding platform. Based on ELM model, we establish Fixed Estimation Panel Data Model respectively according to explicit and implicit factors and take Funding Status (crowdfunding results) as the moderating variable to observe the goal gradient effect. Results indicate that most variables in the central route affect backers' investment behavior positively, while most variables in the periphery route have a negative impact on backers' investment behavior. The Funding Status has a significant negative moderating effect on the explicit variables, and has no significant moderating effect on the implicit information variables of the project. In addition, we upgrade the econometric method used by previous scholars, which could improve the accuracy of the FE model. Furthermore, we find strong support for the herding effect in reward-based crowdfunding and the intensity tends to decrease before the funding goal draws near.


Assuntos
Crowdsourcing/economia , Investimentos em Saúde , Comunicação Persuasiva , Recompensa , Bases de Dados Factuais , Tomada de Decisões , Humanos , Internet , Funções Verossimilhança , Modelos Econômicos , Modelos Psicológicos
19.
PLoS One ; 15(8): e0237882, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32845927

RESUMO

Phylogenetic positions of the genus Longgenacris and one of its members, i.e. L. rufiantennus are controversial. The species boundaries within both of L. rufiantennus+Fruhstorferiola tonkinensis and F. viridifemorata species groups are unclear. In this study, we explored the phylogenetic positions of the genus Longgenacris and the species L. rufiantennus and the relationships among F. viridifemorata group based on the 658-base fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) barcode and the complete sequences of the internal transcribed spacer regions (ITS1 and ITS2) of the nuclear ribosomal DNA. The phylogenies were reconstructed in maximum likelihood framework using IQ-TREE. K2P distances were used to assess the overlap range between intraspecific variation and interspecific divergence. Phylogenetic species concept and NJ tree, K2P distance, the statistical parsimony network as well as the generalized mixed Yule coalescent model (GMYC) were employed to delimitate the species boundaries in L. rufiantennus+F. tonkinensis and F. viridifemorata species groups. The results demonstrated that the genus Longgenacris should be placed in the subfamily Melanoplinae but not Catantopinae, and L. rufiantennus should be a member of the genus Fruhstorferiola but not Longgenacris. Species boundary delimitation confirmed the presence of oversplitting in L. rufiantennus+F. tonkinensis and F. viridifemorata species groups and suggested that each group should be treated as a single species.


Assuntos
Gafanhotos/classificação , Gafanhotos/genética , Filogenia , Animais , Complexo IV da Cadeia de Transporte de Elétrons/genética , Variação Genética , Gafanhotos/anatomia & histologia , Haplótipos/genética , Funções Verossimilhança , Masculino , Modelos Teóricos , Especificidade da Espécie , Dente/anatomia & histologia
20.
PLoS One ; 15(8): e0237146, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32857756

RESUMO

The Global Navigation Satellite System is vulnerable to interference signals that can potentially disable the system, because the signal strength tends to be very weak. Interference such as jamming, which disables the receiver via excessively high signal strength in the satellite navigation frequency band, and spoofing, which induces the receiver to output erroneous position and time data via signals similar to actual navigation signals, disrupt satellite navigation systems. As the threat of interference is increasing, considerable research effort has been expended in an attempt to deal with it in various ways. Spoofing attacks are especially difficult to detect. This paper deals with a technique to detect a spoofing signal and to mitigate attacks on satellite navigation systems. The satellite navigation signal is influenced by the navigation satellite itself and errors due to environmental factors, and spoofing signal detection should be well reflected in the navigation signal. Especially, in the case of mobile receivers, it is not easy to detect a spoofing signal because the exact position of the receiver cannot be known. To detect a spoofing signal, additional hardware may be required; in some cases, heterogeneous sensors, such as inertial sensors, may be used. The technique introduced in this paper effectively discriminates spoofing signals based only on receiver measurements, without the need for additional devices. It generates test statistics based on the pseudorange, which is the measured value of the receiver position, and detects spoofing signals by setting the monitoring interval according to a "sliding window". Because the proposed method uses output data and measurements obtained from the receiver, it can be applied to general receivers at low cost.


Assuntos
Comunicações Via Satélite , Aeronaves , Algoritmos , Distribuição de Qui-Quadrado , Confiabilidade dos Dados , Meio Ambiente , Funções Verossimilhança , Ondas de Rádio , Processamento de Sinais Assistido por Computador
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