Exact results for the Barabasi model of human dynamics

Human activity patterns display a bursty dynamics, with interevent times following a heavy tailed distribution. This behavior has been recently shown to be rooted in the fact that humans assign their active tasks different priorities, a process that can be modeled as a priority queueing system [A.-L. Barabasi, Nature 435, 207 (2005)]. In this work we obtain exact results for the Barabasi model with two tasks, calculating the priority and waiting time distribution of active tasks. We demonstrate that the model has a singular behavior in the extremal dynamics limit, when the highest priority task is selected first. We find that independently of the selection protocol, the average waiting time is smaller or equal to the number of active tasks, and discuss the asymptotic behavior of the waiting time distribution. These results have important implications for understanding complex systems with extremal dynamics.Comment: 4 pages, 4 figures, revte

Circuit QED with a Nonlinear Resonator : ac-Stark Shift and Dephasing

We have performed spectroscopic measurements of a superconducting qubit dispersively coupled to a nonlinear resonator driven by a pump microwave field. Measurements of the qubit frequency shift provide a sensitive probe of the intracavity field, yielding a precise characterization of the resonator nonlinearity. The qubit linewidth has a complex dependence on the pump frequency and amplitude, which is correlated with the gain of the nonlinear resonator operated as a small-signal amplifier. The corresponding dephasing rate is found to be close to the quantum limit in the low-gain limit of the amplifier.Comment: Paper : 4 pages, 3 figures; Supplementary material : 1 page, 1 figur

Carbon footprint in different beef production systems on a southern Brazilian farm: a case study.

The carbon footprint (CF) of beef production is one of the most widely discussed environmental issues within the current agricultural community due to its association with climate change. Because of these relevant and serious concerns, the beef cattle industry is under increasing pressure to reduce production or implement technological changes with significant consequences in terms of beef marketing. The goals of this study were to evaluate the CF per 1 kg of live weight gain (LWG) at the farm gate for different beef production systems in the southern part of Brazil. Aberdeen Angus beef-bred cattle were assigned to one of seven categories: natural grass; improved natural grass; natural grass plus ryegrass; improved natural grass plus sorghum; cultivated ryegrass and sorghum; natural grass supplemented with protein mineralised salt; and natural grass supplemented with protein-energetic mineralised salt. Monte Carlo analysis was employed to analyse the effect of variations of dry matter intake digestibility (DMID), total digestible nutrients (TDN) and crude protein (CP) parameters in methane (CH4) enteric, CH4 manure, nitrous oxide (N2O) manure and N2O N-fertiliser. The method used was a comparative life cycle assessment (LCA) centred on the CF. The CF varied from 18.3 kg CO2 equivalent/kg LWG for the ryegrass and sorghum pasture system to 42.6 kg CO2 equivalent/kg LWG for the natural grass system, including the contributions of cows, calves and steers. Among all grassland-based cattle farms, production systems with DMID from 52 to 59% achieved the lowest CO2 emissions and the highest feed conversion rate, thereby generating lower CH4 and N2O emissions per production system. Because the feed intake and feed conversion rate are one of the most important production parameters in beef cattle production with an obvious risk of data uncertainty, accurate feed data, which include quantity and quality, are important in estimates of CF for LWG. The choice of adequate feeding strategies to mitigate greenhouse gas (GHG) emissions may result in better environmental advantages

Role of Activity in Human Dynamics

The human society is a very complex system; still, there are several non-trivial, general features. One type of them is the presence of power-law distributed quantities in temporal statistics. In this Letter, we focus on the origin of power-laws in rating of movies. We present a systematic empirical exploration of the time between two consecutive ratings of movies (the interevent time). At an aggregate level, we find a monotonous relation between the activity of individuals and the power-law exponent of the interevent-time distribution. At an individual level, we observe a heavy-tailed distribution for each user, as well as a negative correlation between the activity and the width of the distribution. We support these findings by a similar data set from mobile phone text-message communication. Our results demonstrate a significant role of the activity of individuals on the society-level patterns of human behavior. We believe this is a common character in the interest-driven human dynamics, corresponding to (but different from) the universality classes of task-driven dynamics.Comment: 5 pages, 6 figures. Accepted by EP

Espectroscopia no infravermelho na análise da composição química de diferentes genótipos de Trifolium repens.

Abstract: White clover, Trifolium repens L., is a perennial legume with large forage importance. In the Embrapa Southern Livestock four genotypes has been studied (CPPSUL, Entrevero, Sintético 1 and Sintético 2) which none chemical characterization has been done. For another point of view, the infrared spectroscopy is a quickly, low cost method for identification of chemical compounds. Thereby, this work was made valuation of spectroscopy application and analyses composition of silica, condensates tannins and cellulose. Four genotypes were dry, 20 samples of which one were analyze separately on infrared spectrometer (Spectrum Perkin Elmer) and the graphical examined OriginLab software. The samples showed different intensity, therefore distinct compositions. The silica composition of Entrevero, Sintético 1 e Sintético 2 cooperating to CPPSUL was respectively 1.16, 1.14 e 1.37, for cellulose was 1.51, 1.08 e 2.07, and for condensates tannins 1.58 e 0.96 e 2.45. The infrared spectroscopy demonstrate like interesting analytical instrument for identification chemical composition being quickly, reproducible, without preparation and does not destroy the samples.5 p. Zootecnia Brasil 2018

Uso de sistema de informação para aprimorar o processo de informatização do herbário CNPO da Embrapa Pecuária Sul.

O trabalho objetivou a criação de um método de estruturação dos dados existentes no Herbário CNPO para possibilitar a sua integração ao banco de dados do Sistema de Informação da Biodiversidade Brasileira (SiBBr), bem como realizar o levantamento de Poaceae e Fabaceae inseridas no acervo.Claudia Cristina Gulias Gomes, editora técnica

Manutenção da variabilidade genética de acessos de Bromus auleticus.

Bromus auleticus Trin. ex Nees, cevadilha vacariana, é uma gramínea forrageira nativa considerada de ampla disseminação na América do Sul Temperada, porém de baixa frequência de ocorrência nos campos naturais

Introdução às ciências zootécnica e botânica para alunos do quarto ano em visita à Embrapa Pecuária Sul.

Abstract: Abstract: Research centers are very important to contribute and promote community scientific literacy of children impacts teaching in later grades, promotes the development of conscious citizens regarding the valuation of animal husbandry and food production. Thus, Embrapa has a vital role in society linked to food security through community interaction with agricultural research. The aim of this work was to connect local urban students with animal and botanical sciences and the origin of food, through sensorial and motor skills for a learning associated with daily life. A thematic visit was carried out by 50 students 9-11 years old from the Nossa Senhora Auxiliadora School, Bagé-RS, to Embrapa Southern Livestock, for a variety of forages and ruminants. The children attended the lecture in appropriate language about diet and animal category, different dairy products, animal fat where they saw flipcharts, manipulated dairy packaging, concentrate and roughage ingredients; asked the speakers more than 20 questions. Afterwards, they observed the germoplasm bank: exotic, white clover (Trifolium repens L.), Sudan grass (Sorghum sudanense (Piper) Stapf) BRS Birdsfoot Trefoil (Lotus corniculatus L.) BRS Posteiro; and Herbarium-CNPO with native exsiccates. The high participation of students demonstrated a good receptivity to the actives methodologies.5 p. Zootecnia Brasil 2018

Herbário CNPO e Banco Ativo de Germoplasma de Forrageiras do Sul do Brasil: interface para coleta, conservação e informatização.

Resumo.Fernando Flores Cardoso, Daniel Portella Montardo, José Carlos Ferrugem Moraes, Marcos Flávio Silva Borba, Sandro da Silva Camargo, editores técnicos

Manejo de campo nativo e levantamento de espécies em área experimental.

O campo nativo apresenta uma grande diversidade biológica, onde a maioria das espécies encontradas, além de constituir o patrimônio genético do Bioma Pampa, possui bom potencial forrageiro. O objetivo do presente trabalho foi realizar levantamentos de plantas com potencial forrageiro e as indesejáveis ocorrentes na área de estudo, bem como acompanhar a regeneração das espécies do banco de sementes local. O trabalho foi executado na Embrapa Pecuária Sul, Bagé-RS, no potreiro 13 A1, local onde desde a primavera de 2015 realiza-se o acompanhamento da ocorrência de espécies, as quais foram divididas em duas categorias: forrageiras e indesejáveis. Nos períodos setembro de 2015, abril e agosto de 2016 foi realizada a integração lavoura-pecuária (ILP), e o levantamento de espécies em três diferentes estações (primavera-após colheita da soja, em 2015; outono e inverno de 2016). Em 2015 o levantamento apontou que havia predominância de azevém, entretanto, no outono e inverno de 2016 foram identificadas 35 espécies. Na segunda etapa, em 2019, houve predominância significativa na observação de capim-annoni. Por outro lado, ocorreram em menor frequência 25 espécies: seis forrageiras e 19 indesejáveis. Dentre estas, as famílias de maior frequência foram Poaceae, Asteraceae e Fabaceae. Conclui-se que as espécies com bom potencial forrageiro foram regeneradas na área, sendo grande parte delas oriundas do banco de sementes do solo, além de outras plantas semeadas para o melhoramento do campo. Deve-se considerar a necessidade de um melhor acompanhamento da área, quantificando e aprofundando o estudo das espécies