Unbiased approximations of products of expectations

We consider the problem of approximating the product of n expectations with respect to a common probability distribution μ⁠. Such products routinely arise in statistics as values of the likelihood in latent variable models. Motivated by pseudo-marginal Markov chain Monte Carlo schemes, we focus on unbiased estimators of such products. The standard approach is to sample N particles from μ and assign each particle to one of the expectations; this is wasteful and typically requires the number of particles to grow quadratically with the number of expectations. We propose an alternative estimator that approximates each expectation using most of the particles while preserving unbiasedness, which is computationally more efficient when the cost of simulations greatly exceeds the cost of likelihood evaluations. We carefully study the properties of our proposed estimator, showing that in latent variable contexts it needs only O(n) particles to match the performance of the standard approach with O(n^2) particles. We demonstrate the procedure on two latent variable examples from approximate Bayesian computation and single-cell gene expression analysis, observing computational gains by factors of about 25 and 450, respectively

FATORES CRÍTICOS DE SUCESSO DE PROGRAMAS DE EDUCAÇÃO A DISTÂNCIA VIA INTERNET

Empresas e instituições de ensino têm realizado investimentos significativos na implementação de programas de Educação a Distância (EAD), que utilizam a internet como principal tecnologia de informação e comunicação. O atual cenário econômico, cultural e tecnológico favorece a criação de um mercado eletrônico de aprendizagem, justificando tais investidas. A Educação a Distância aparenta mover-se em direção à internet, mas o caminho é difícil,por causa das muitas incertezas. Estas incertezas, com o grande número de variáveis envolvidas nos programas EAD via internet, dificultam para gestores que se mantenha o foco nos pontos essenciais. Assim, o objetivo deste trabalho é identificar os fatores críticos de sucesso dos programas de educação a distância via internet. Para isso foi realizado um questionário de perguntas com estudantes da UNIASSELVI (Polo de Porto Alegre), que responderam questões sobre o AVA (Ambiente Virtual de Aprendizagem), sobre a qualidade da informação, usabilidade, interatividade, velocidade, arquitetura da informação, confiabilidadee segurança. A partir destes resultados, teremos uma conclusão sobre a influência deste método de estudo e sua contribuição humana. Assim é mais seguro afirmar que, sem prestar atenção aos sete fatores críticos identificados, a probabilidade de que aconteçam problemas com um programa de educação a distância é alta

Pulverização pneumática eletrostática em videiras ‘Niágara Branca’ e ‘Rosada’

Vine cultivation is the target of several pathogens such as fungi, against which synthetic fungicides are commonly used, so studies have been made on methods to decrease the volume of pesticides to reduce problems such as phytotoxicity, costs and environmental damage. Thus, the objective of this research was to verify the effect of electrostatic pneumatic spraying on Niagara Branca and Rosada grapevines in Laranjeiras do Sul, PR. Fungicidal treatment was carried out on grapevine cultivars (Niagara Branca and Rosada), applying them with present and absent load. The application volume, the seed coat, the severity of diseases in plants and bunches, number of bunches and bunches with lesions per plant, number of berries per bunch, length and bunch diameter, fresh mass, soluble solids, titratable acidity, fruit epidermal coloring, total phenolic compounds, total anthocyanins, loss of mass, and determination of appearance. This study was conducted under a completely randomized blocks design, for field variable responses and physical-chemical and phytochemical characterization of fruits, consisting of two factors (2x2), a load factor and another cultivar. For the variables loss of mass and determination of appearance, the factorial scheme was 2x2x5, where Niagara cultivar and storage periods (0, 2, 4, 6 and 8 days) were a load factor. The data were subjected to analysis of variance, and when significant they were compared by the Tukey test (p<0.05) through the statistics software Assistat. Different cultivars showed mass of the affected fruits in different ways, as well as the appearance of the fruits, according to the storage periods evaluated. Spraying with the presence of filler had an effect on the color of the epidermis and bunch length on 'Niagara Branca', also promoted a higher content of anthocyanins and resulted in a lower volume of spray solution applied with indifferent coverage, and therefore electrostatic spraying showed an effect on the application.O cultivo de videira é alvo de diversos agentes patogênicos, como os fungos, para controle geralmente são utilizados fungicidas sintéticos, então pesquisas tem testado métodos para diminuir o volume de defensivos agrícolas para reduzir problemas como fitotoxidez, custos e danos ambientais. Assim, objetivou-se com este trabalho verificar o efeito da pulverização pneumática eletrostática em videiras cultivares Niágara Branca e Rosada em Laranjeiras do Sul, PR. Realizou-se tratamento fungicida em cultivares de videira (Niágara Branca e Rosada), aplicando-os com carga presente e ausente. Foi avaliado o volume de calda de aplicação, cobertura da calda, severidade de doenças nas plantas e cachos, número de cachos e de cachos com lesões por planta, número de bagas por cacho, comprimento e diâmetro de cacho, massa fresca, sólidos solúveis, acidez titulável, coloração da epiderme do fruto, compostos fenólicos totais, antocianinas totais, perda de massa e a determinação da aparência. O delineamento foi em blocos inteiramente casualizados, para variáveis respostas de campo e caracterização físico-química e fitoquímica das frutas, constou de dois fatores (2x2), um fator carga e outro cultivar. Para as variáveis perda de massa e determinação da aparência o esquema fatorial foi 2x2x5, sendo um fator carga, cultivar de Niágara e períodos de armazenamento (0, 2, 4, 6 e 8 dias). Os dados foram submetidos à análise de variância, quando significativos, comparados pelo teste de Tukey (p<0,05) através do software estatístico Assistat. Diferentes cultivares apresentaram massa dos frutos afetadas de maneiras distintas, assim como a aparência dos frutos, de acordo com os períodos de armazenagem avaliados. A pulverização com presença de carga atuou na coloração da epiderme e comprimento de cacho na ‘Niágara Branca’, também promoveu maior teor de antocianinas e resultou em menor volume de calda aplicado com cobertura indiferente, portanto a pulverização eletrostática demonstrou efeito na aplicação

GORA: Goodput Optimal Rate Adaptation for 802.11 using Medium Status Estimation,”

Abstract-Rate Adaptation for 802.11 has been deeply investigated in the past, but the problem of achieving optimal Rate Adaptation with respect not only to channel-related errors but also to contention-related issues (i.e., collisions and variations in medium access times) is still unsolved. In this paper we address this issue by proposing 1) a practical definition of the Medium Status in a multi-user 802.11 scenario in terms of channel errors, MAC collisions and packet service times, and a method for its estimation based on measurements; 2) an analytical model of the goodput performance as a function of the Medium Status; 3) a rate adaptation algorithm, called Goodput Optimal Rate Adaptation (GORA), which is based on this model. Unlike other Rate Adaptation schemes proposed in literature, which require either modifications to the IEEE 802.11 standard or cooperation among nodes, GORA is totally stand-alone and standard compliant. In fact, the Medium Status Estimation used by GORA is obtained by using standard MAC counters that are commonly collected by commercial MAC drivers, and no explicit interactions with the other devices in the network is required. Therefore, GORA offers the advantage of being readily deployable on real devices. The performance of GORA is evaluated through NS2 simulations which reveal that, as expected, GORA outperforms other wellknown Rate Adaptation algorithms in several scenarios and can be used as a new reference benchmark

Dataset of characteristic remanent magnetization and magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform)

This data article describes data of magnetic stratigraphy and anisotropy of isothermal remanent magnetization (AIRM) from "Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system" [1]. Acquisition of isothermal magnetization on pilot samples and anisotropy of isothermal remanent magnetization are reported as raw data; magnetostratigraphic data are reported as characteristic magnetization (ChRM).info:eu-repo/semantics/publishedVersio

Comparative transcriptome and metabolite survey reveal key pathways involved in the control of the chilling injury disorder superficial scald in two apple cultivars, ‘Granny Smith’ and ‘Ladina’

The low temperature normally applied to prevent fruit decay during the storage of apples, can also triggers the onset of a chilling injury disorder known as superficial scald. In this work, the etiology of this disorder and the mechanism of action of two preventing strategies, such as the application of 1-MCP (1-methylcyclopropene) and storage at low oxygen concentration in ‘Granny Smith’ and ‘Ladina’ apple cultivars were investigated. The metabolite assessment highlighted a reorganization of specific metabolites, in particular flavan-3-ols and unsaturated fatty acids, while the genome-wide transcriptomic analysis grouped the DEGs into four functional clusters. The KEGG pathway and GO enrichment analysis, together with the gene-metabolite interactome, showed that the treatment with 1-MCP prevented the development of superficial scald by actively promoting the production of unsaturated fatty acids, especially in ‘Granny Smith’. ‘Ladina’, more susceptible to superficial scald and less responsive to the preventing strategies, was instead characterized by a higher accumulation of very long chain fatty acids. Storage at low oxygen concentration stimulated a higher accumulation of ethanol and acetaldehyde together with the expression of genes involved in anaerobic respiration, such as malate, alcohol dehydrogenase and pyruvate decarboxylase in both cultivars. Low oxygen concentration, likewise 1-MCP, through a direct control on ethylene prevented the onset of superficial scald repressing the expression of PPO, a gene encoding for the polyphenol oxidase enzyme responsible of the oxidation of chlorogenic acid. Moreover, in ‘Granny Smith’ apple, the expression of three members of the VII subgroups of ERF genes, encoding for elements coordinating the acclimation process to hypoxia in plants was observed. The global RNA-Seq pattern also elucidated a specific transcriptomic signature between the two cultivars, disclosing the effect of the different genetic background in the control of this disorder