Variational inference and sparsity in high-dimensional deep Gaussian mixture models

Gaussian mixture models are a popular tool for model-based clustering, and mixtures of factor analyzers are Gaussian mixture models having parsimonious factor covariance structure for mixture components. There are several recent extensions of mixture of factor analyzers to deep mixtures, where the Gaussian model for the latent factors is replaced by a mixture of factor analyzers. This construction can be iterated to obtain a model with many layers. These deep models are challenging to fit, and we consider Bayesian inference using sparsity priors to further regularize the estimation. A scalable natural gradient variational inference algorithm is developed for fitting the model, and we suggest computationally efficient approaches to the architecture choice using overfitted mixtures where unnecessary components drop out in the estimation. In a number of simulated and two real examples, we demonstrate the versatility of our approach for high-dimensional problems, and demonstrate that the use of sparsity inducing priors can be helpful for obtaining improved clustering results.Peer Reviewe

Variational Inference and Sparsity in High-Dimensional Deep Gaussian Mixture Models

Gaussian mixture models are a popular tool for model-based clustering, and mixtures of factor analyzers are Gaussian mixture models having parsimonious factor covariance structure for mixture components. There are several recent extensions of mixture of factor analyzers to deep mixtures, where the Gaussian model for the latent factors is replaced by a mixture of factor analyzers. This construction can be iterated to obtain a model with many layers. These deep models are challenging to fit, and we consider Bayesian inference using sparsity priors to further regularize the estimation. A scalable natural gradient variational inference algorithm is developed for fitting the model, and we suggest computationally efficient approaches to the architecture choice using overfitted mixtures where unnecessary components drop out in the estimation. In a number of simulated and two real examples, we demonstrate the versatility of our approach for high-dimensional problems, and demonstrate that the use of sparsity inducing priors can be helpful for obtaining improved clustering results

Deep mixture of linear mixed models for complex longitudinal data

Mixtures of linear mixed models are widely used for modelling longitudinal data for which observation times differ between subjects. In typical applications, temporal trends are described using a basis expansion, with basis coefficients treated as random effects varying by subject. Additional random effects can describe variation between mixture components, or other known sources of variation in complex experimental designs. A key advantage of these models is that they provide a natural mechanism for clustering, which can be helpful for interpretation in many applications. Current versions of mixtures of linear mixed models are not specifically designed for the case where there are many observations per subject and a complex temporal trend, which requires a large number of basis functions to capture. In this case, the subject-specific basis coefficients are a high-dimensional random effects vector, for which the covariance matrix is hard to specify and estimate, especially if it varies between mixture components. To address this issue, we consider the use of recently-developed deep mixture of factor analyzers models as the prior for the random effects. The resulting deep mixture of linear mixed models is well-suited to high-dimensional settings, and we describe an efficient variational inference approach to posterior computation. The efficacy of the method is demonstrated on both real and simulated data

Efeitos do desmatamento no microclima em uma área de Transição Cerrado-Amazônia

The Cerrado-Amazon Transition region has a high deforested area in Brazil. Given the importance of the forest in maintaining the climate of this region, were evaluated the patterns of micrometeorological variables in forested and deforested areas in the Cerrado-Amazon Transition region in Mato Grosso, Brazil. Precipitation, solar radiation, average, minimum and maximum air temperature, relative air humidity, soil temperature and wind speed were measured into a forest (FOR) and in a deforested area (DEF). Precipitation in the studied region has a hyper-seasonal pattern with 95% of the volume in the wet season (October to April), which influenced the seasonality of the micrometeorological variables. Solar radiation in DEF was 8-folds higher than in FOR, air temperature in DEF was up to 11% higher than in FOR, relative humidity in FOR was up to 14% higher than in DEF, soil temperature in DEF was 18% greater than in FOR and wind speed in DEF was 22-folds greater than in FOR. Deforestation significantly influenced the seasonality and magnitude of the analyzed micrometeorological variables.La región de Transición Cerrado-Amazonía tiene una alta área deforestada en Brasil. Dada la importancia del bosque en el mantenimiento del clima de esta región, evaluamos los patrones de variables micrometeorológicas en áreas boscosas y deforestadas en la región de Transición Cerrado-Amazonía en Mato Grosso, Brasil. Se midió la precipitación, la radiación solar, la temperatura del aire media, mínima y máxima, la humedad relativa del aire, la temperatura del suelo y la velocidad del viento dentro de un bosque (FOR) y en un área deforestada (DEF). La precipitación en la región de estudio presenta un patrón hiperestacional con 95% del volumen en la época de lluvias (octubre a abril), lo que influyó en la estacionalidad de las variables micrometeorológicas. La radiación solar en DEF fue 8 veces mayor que en STR, la temperatura del aire en DEF fue hasta un 11% mayor que en STR, la humedad relativa en FOR fue hasta un 14% mayor que en DEF, la temperatura del suelo en DEF fue de 18 % mayor que en STR y la velocidad del viento en DEF fue 22 veces mayor que en STR. La deforestación influyó significativamente en la estacionalidad y magnitud de las variables micrometeorológicas analizadas.A região de Transição Cerrado-Amazônia possui uma elevada área desmatada no Brasil. Dada a importância da floresta na manutenção do clima desta região, foram avaliados os padrões de variáveis micrometeorológicas em áreas florestadas e desmatadas na região de Transição Cerrado-Amazônia em Mato Grosso, Brasil. A precipitação, radiação solar, temperatura média, mínima e máxima do ar, umidade relativa do ar, temperatura do solo e velocidade do vento foram medidas no interior de uma floresta (FOR) e em uma área desmatada (DEF). A precipitação na região estudada apresenta um padrão hipersazonal com 95% do volume na estação chuvosa (outubro a abril), o que influenciou na sazonalidade das variáveis micrometeorológicas. A radiação solar em DEF foi 8 vezes maior que em FOR, a temperatura do ar em DEF foi até 11% maior que em FOR, a umidade relativa em FOR foi até 14% maior que em DEF, a temperatura do solo em DEF foi 18% maior que em FOR e a velocidade do vento em DEF foi 22 vezes maior do que em FOR. O desmatamento influenciou significativamente a sazonalidade e magnitude das variáveis micrometeorológicas analisadas

Isotopic and DNA analyses reveal multiscale PPNB mobility and migration across Southeastern Anatolia and the Southern Levant

Growing reliance on animal and plant domestication in the Near East and beyond during the Pre-Pottery Neolithic B (PPNB) (the ninth to eighth millennium BC) has often been associated with a “revolutionary” social transformation from mobility toward more sedentary lifestyles. We are able to yield nuanced insights into the process of the Neolithization in the Near East based on a bioarchaeological approach integrating isotopic and archaeogenetic analyses on the bone remains recovered from Nevalı Çori, a site occupied from the early PPNB in Turkey where some of the earliest evidence of animal and plant domestication emerged, and from Ba'ja, a typical late PPNB site in Jordan. In addition, we present the archaeological sequence of Nevalı Çori together with newly generated radiocarbon dates. Our results are based on strontium (87Sr/86Sr), carbon, and oxygen (δ18O and δ13Ccarb) isotopic analyses conducted on 28 human and 29 animal individuals from the site of Nevalı Çori. 87Sr/86Sr results indicate mobility and connection with the contemporaneous surrounding sites during the earlier PPNB prior to an apparent decline in this mobility at a time of growing reliance on domesticates. Genome-wide data from six human individuals from Nevalı Çori and Ba'ja demonstrate a diverse gene pool at Nevalı Çori that supports connectedness within the Fertile Crescent during the earlier phases of Neolithization and evidence of consanguineous union in the PPNB Ba'ja and the Iron Age Nevalı Çori

Surface albedo and temperature models for surface energy balance fluxes and evapotranspiration using SEBAL and Landsat 8 over Cerrado-Pantanal, Brazil

The determination of the surface energy balance fluxes (SEBFs) and evapotranspiration (ET) is fundamental in environmental studies involving the effects of land use change on the water requirement of crops. SEBFs and ET have been estimated by remote sensing techniques, but with the operation of new sensors, some variables need to be parameterized to improve their accuracy. Thus, the objective of this study is to evaluate the performance of algorithms used to calculate surface albedo and surface temperature on the estimation of SEBFs and ET in the Cerrado-Pantanal transition region of Mato Grosso, Brazil. Surface reflectance images of the Operational Land Imager (OLI) and brightness temperature (Tb) of the Thermal Infrared Sensor (TIRS) of the Landsat 8, and surface reflectance images of the MODIS MOD09A1 product from 2013 to 2016 were combined to estimate SEBF and ET by the surface energy balance algorithm for land (SEBAL), which were validated with measurements from two flux towers. The surface temperature (Ts) was recovered by different models from the Tb and by parameters calculated in the atmospheric correction parameter calculator (ATMCORR). A model of surface albedo (asup) with surface reflectance OLI Landsat 8 developed in this study performed better than the conventional model (acon) SEBFs and ET in the Cerrado-Pantanal transition region estimated with asup combined with Ts and Tb performed better than estimates with acon. Among all the evaluated combinations, SEBAL performed better when combining asup with the model developed in this study and the surface temperature recovered by the Barsi model (Tsbarsi ). This demonstrates the importance of an asup model based on surface reflectance and atmospheric surface temperature correction in estimating SEBFs and ET by SEBAL

INDIOS TUPI DO INTERIOR DA PARAÍBA E SEUS FLUXOS MIGRATÓRIOS

Consolidou-se, entre as cátedras da historiografia brasileira, a concepção de que existia uma separaçãoconsolidada entre os índios que povoavam o território que hoje denominámos Brasil, nos tempos dacolonização lusa: os chamados Tapuios ocupavam as sertanias, ao passo que os Tupi limitavam-se aolitoral. Isso posto, o artigo a seguir tem como objetivo apresentar, sintética e introdutoriamente, as novasevidências arqueológicas que atestam a presença inequívoca de índios Tupis no interior da Paraíba. Naliteratura de época colonial, ademais, encontramos documentos que comprovam a presença de aldeias Tupisem localidades no interior do que hoje é o Nordeste do Brasil, como as Aldeias de Tabajaras na Serra daIbiapaba no Ceará e posteriormente, na própria Paraíba (Capitania Real da Parahyba). Assim, com base nosmais recentes achados arqueológicos do interior da Paraíba (em cidades do Alto Sertão, inclusivamente,conhecidos redutos Cariri/Tarairiu) nomeadamente urnas funerárias Tupi, é possível pôr em causa a jáconsolidada tese, o que suscita novos questionamentos, em especial a razão da escassa documentaçãoatestando tal prolífica presença, impondo também dúvida sobre as formas e rotas dessa ocupação Tupi dassertanias, outrora tida como inexistente ou demasiado rara. O trabalho que se segue não traz respostaspara tais questões, uma vez que ainda não as tem. Com o desenvolvimento das pesquisas, no entanto,espera-se que mais esta faceta da Paraíba pretérita seja suficientemente elucidada nos vindouros anos

INDIOS TUPI DO INTERIOR DA PARAÍBA E SEUS FLUXOS MIGRATÓRIOS

Consolidou-se, entre as cátedras da historiografia brasileira, a concepção de que existia uma separaçãoconsolidada entre os índios que povoavam o território que hoje denominámos Brasil, nos tempos dacolonização lusa: os chamados Tapuios ocupavam as sertanias, ao passo que os Tupi limitavam-se aolitoral. Isso posto, o artigo a seguir tem como objetivo apresentar, sintética e introdutoriamente, as novasevidências arqueológicas que atestam a presença inequívoca de índios Tupis no interior da Paraíba. Naliteratura de época colonial, ademais, encontramos documentos que comprovam a presença de aldeias Tupisem localidades no interior do que hoje é o Nordeste do Brasil, como as Aldeias de Tabajaras na Serra daIbiapaba no Ceará e posteriormente, na própria Paraíba (Capitania Real da Parahyba). Assim, com base nosmais recentes achados arqueológicos do interior da Paraíba (em cidades do Alto Sertão, inclusivamente,conhecidos redutos Cariri/Tarairiu) nomeadamente urnas funerárias Tupi, é possível pôr em causa a jáconsolidada tese, o que suscita novos questionamentos, em especial a razão da escassa documentaçãoatestando tal prolífica presença, impondo também dúvida sobre as formas e rotas dessa ocupação Tupi dassertanias, outrora tida como inexistente ou demasiado rara. O trabalho que se segue não traz respostaspara tais questões, uma vez que ainda não as tem. Com o desenvolvimento das pesquisas, no entanto,espera-se que mais esta faceta da Paraíba pretérita seja suficientemente elucidada nos vindouros anos

Estudos das Itacoatiaras da Paraíba: Pedra do Ingá e Pedra de Retumba

Trabalho apresentado no Simpósio 1 da VI Reunião da SAB Nordeste 202