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

Storage and Retrieval of a Microwave Field in a Spin Ensemble

We report the storage and retrieval of a small microwave field from a superconducting resonator into collective excitations of a spin ensemble. The spins are nitrogen-vacancy centers in a diamond crystal. The storage time of the order of 30 ns is limited by inhomogeneous broadening of the spin ensemble.Comment: 4 pages + supplementary material. Submitted to PR

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

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

Healthy Pacific Grandparents: A Participatory Action Research Project Exploring Ageing Well Amongst Pacific People in New Zealand

The New Zealand older adult population (aged 65+ years) is growing at a faster rate than the younger population, with many of those in the later years living much longer. The proportion of older Pacific people is forecast to reach 4.1% of the country’s total population within the next two decades, highlighting the importance of research focused on ageing Pacific populations. This article sets out the research protocol and methods for the Pacific Islands Families: Healthy Pacific Grandparents’ Study, which aims to investigate older Pacific people’s viewpoints on ageing to identify specific cultural values, perspectives and understandings as the Pacific population in New Zealand ages. The study will recruit and utilize participants from a grandparent cohort that is nested within the families of the longitudinal Pacific Islands Families Study. This study uses a Participatory Action Research approach to position the participants in a leadership role where they are co-researchers involved in both the research and the implementation of recommendations. Utilizing a transformative research process will bring older Pacific people together to define for themselves their needs and their experiences, identify any areas of shortcoming, and support the implementation of solutions through strategic and informed actions

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

Tumor Sink Effect with Prostate-Specific Membrane Antigen-Targeted Theranostics in Patients with Metastatic Castration-Resistant Prostate Cancer: Intra-Individual Evaluations

“Tumor sink effects”, decreased physiological uptake of radiopharmaceuticals due to sequestration by a tumor, may impact radioligand therapy (RLT) toxicity and dosing. We investigated these effects with prostate-specific membrane antigen (PSMA)-targeted radiopharmaceuticals in the healthy organs-at-risk (the parotid glands, kidneys, liver, and spleen) of 33 patients with metastatic castration-resistant prostate cancer (mCRPC). We retrospectively performed three intra-individual comparisons. First, we correlated changes from baseline to post-RLT (after two 177-lutetium (177Lu)-PSMA-617 cycles) in total lesional PSMA (∆TLP) and organ mean standardized uptake values (∆SUVmean). Second, in 25 RLT responders, we compared the organ SUVmean post-RLT versus that at baseline. Lastly, we correlated the baseline TLP and organ SUVmean. Data were acquired via 68-gallium-PSMA-11 positron emission tomography before the first and after the second 177Lu-PSMA-617 cycle. In the parotid glands and spleen, ∆TLP and ∆SUVmean showed a significant inverse correlation (r = −0.40, p = 0.023 and r = −0.36, p = 0.042, respectively). Additionally, in those tissues, the median organ SUVmean rose significantly from baseline after the response to RLT (p ≤ 0.022), and the baseline TLP and SUVmean were significantly negatively correlated (r = −0.44, p = 0.01 and r = −0.42, p = 0.016, respectively). These observations suggest tumor sink effects with PSMA-targeted radiopharmaceuticals in the salivary glands and spleen of patients with mCRPC

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

Modeling bursts and heavy tails in human dynamics

Current models of human dynamics, used from risk assessment to communications, assume that human actions are randomly distributed in time and thus well approximated by Poisson processes. We provide direct evidence that for five human activity patterns the timing of individual human actions follow non-Poisson statistics, characterized by bursts of rapidly occurring events separated by long periods of inactivity. We show that the bursty nature of human behavior is a consequence of a decision based queuing process: when individuals execute tasks based on some perceived priority, the timing of the tasks will be heavy tailed, most tasks being rapidly executed, while a few experiencing very long waiting times. We discuss two queueing models that capture human activity. The first model assumes that there are no limitations on the number of tasks an individual can hadle at any time, predicting that the waiting time of the individual tasks follow a heavy tailed distribution with exponent alpha=3/2. The second model imposes limitations on the queue length, resulting in alpha=1. We provide empirical evidence supporting the relevance of these two models to human activity patterns. Finally, we discuss possible extension of the proposed queueing models and outline some future challenges in exploring the statistical mechanisms of human dynamics.Comment: RevTex, 19 pages, 8 figure