Social networks: evolving graphs with memory dependent edges

The plethora, and mass take up, of digital communication tech- nologies has resulted in a wealth of interest in social network data collection and analysis in recent years. Within many such networks the interactions are transient: thus those networks evolve over time. In this paper we introduce a class of models for such networks using evolving graphs with memory dependent edges, which may appear and disappear according to their recent history. We consider time discrete and time continuous variants of the model. We consider the long term asymptotic behaviour as a function of parameters controlling the memory dependence. In particular we show that such networks may continue evolving forever, or else may quench and become static (containing immortal and/or extinct edges). This depends on the ex- istence or otherwise of certain infinite products and series involving age dependent model parameters. To test these ideas we show how model parameters may be calibrated based on limited samples of time dependent data, and we apply these concepts to three real networks: summary data on mobile phone use from a developing region; online social-business network data from China; and disaggregated mobile phone communications data from a reality mining experiment in the US. In each case we show that there is evidence for memory dependent dynamics, such as that embodied within the class of models proposed here.

Climate spectrum estimation in the presence of timescale errors.

We introduce an algorithm (called REDFITmc2) for spectrum estimation in the presence of timescale errors. It is based on the Lomb-Scargle periodogram for unevenly spaced time series, in combination with the Welch's Overlapped Segment Averaging procedure, bootstrap bias correction and persistence estimation. The timescale errors are modelled parametrically and included in the simulations for determining (1) the upper levels of the spectrum of the red-noise AR(1) alternative and (2) the uncertainty of the frequency of a spectral peak. Application of REDFITmc2 to ice core and stalagmite records of palaeoclimate allowed a more realistic evaluation of spectral peaks than when ignoring this source of uncertainty. The results support qualitatively the intuition that stronger effects on the spectrum estimate (decreased detectability and increased frequency uncertainty) occur for higher frequencies. The surplus information brought by algorithm REDFITmc2 is that those effects are quantified. Regarding timescale construction, not only the fixpoints, dating errors and the functional form of the age-depth model play a role. Also the joint distribution of all time points (serial correlation, stratigraphic order) determines spectrum estimation.

Modelling the time-evolution of phytoplankton size spectra from satellite remote sensing

A dynamic size-structured model is developed for phytoplankton and nutrients in the oceanic mixed layer and applied to extract phytoplankton biomass at discrete size fractions from remotely sensed, ocean-colour data. General relationships between cell size and biophysical processes (such as sinking, grazing, and primary production) of phytoplankton were included in the model through a bottom–up approach. Time-dependent, mixed-layer depth was used as a forcing variable, and a sequential data-assimilation scheme was implemented to derive model trajectories. From a given time-series, the method produces estimates of size-structured biomass at every observation, so estimates seasonal succession of individual phytoplankton size, derived here from remote sensing for the first time. From these estimates, normalized phytoplankton biomass size spectra over a period of 9 years were calculated for one location in the North Atlantic. Further analysis demonstrated that strong relationships exist between the seasonal trends of the estimated size spectra and the mixed-layer depth, nutrient biomass, and total chlorophyll. The results contain useful information on the time-dependent biomass flux in the pelagic ecosystem.

Aumento dos preços dos combustíveis no país: um processo decisório racional?

Decisões são tomadas de diversas formas e em todos os momentos, mas foi o francês Henry Fayol que propôs um modelo estruturado para essa tomada de decisão, definindo o papel dos dirigentes e suas responsabilidades na administração da empresa. No desenvolvimento do trabalho, foram estudados diversos modelos de processo decisório, como o modelo clássico racionalista, o modelo da racionalidade limitada, o modelo político, as coalizões envolvidas no processo, teorias de responsabilidade social corporativa, teorias de governança corporativa, entre outros. À luz destes modelos e baseado na missão da Petrobras, de ser uma empresa segura e rentável, o autor faz uma suposição e enquadra o processo decisório da empresa no modelo clássico racionalista, focado na maximização dos lucros e resultados. Devido ao tamanho da empresa e à diversidade de assuntos para a tomada de decisão, o autor foca seus estudos na área de Abastecimento da Petrobras e analisa o processo de tomada de decisão para o aumento dos preços dos combustíveis, com o objetivo de avaliar a veracidade da sua suposição. A metodologia de pesquisa é baseada em uma pesquisa bibliográfica e investigação documental para avaliar se o modelo de tomada de decisão é realmente racional, ou se existem influências ou fatores externos que levam a um novo modelo de processo decisório. Após comparar o modelo racional com os dados e realizações da empresa, o autor faz uma triangulação de métodos, incluindo uma pesquisa de campo para avaliar a percepção dos gestores e stakeholders sobre o modelo de tomada de decisão da empresa. O autor entrevista 11 funcionários da Petrobras e 10 stakeholders externos com o intuito de coletar percepções sobre o processo decisório da Cia., finalizando com uma análise qualitativa dos dados baseada na técnica de análise de conteúdo. Com os resultados da pesquisa, o autor comprova, por meio de documentos da empresa, que a Diretoria Executiva da Petrobras é a responsável pela aprovação da política de preços da Cia. Dentre os fatores de influência no processo decisório da empresa, a inflação foi a de maior destaque, mostrando o viés político na relação entre o governo e a empresa. A política de preços da Cia. continua sendo de médio e longo prazo, acarretando em prejuízos no curto prazo para a área de Abastecimento da Petrobras. Após alcançar todos os objetivos intermediários do trabalho, o autor conclui que a suposição inicial é falsa e que o processo decisório para o aumento dos preços dos combustíveis na Petrobras se aproxima muito mais dos modelos de racionalidade limitada e político, com enfoque nos stakeholders e na competitividade do que do modelo clássico racionalista.

Níveis de homocisteína e desempenho cognitivo em uma amostra populacional de idosos da cidade do Natal-RN

The imprecision of the frontier that separates those cognitive deficits inherent to the human physiological aging process from those which represent the early signs of nervous system degenerative pathologies ,very prevalent among the elderly, has brought attention to the need of studies aiming to establish clinical and/or laboratorial criteria to allow this differentiation. Elderly people living in poor and developing countries are frequently exposed to precarious socioeconomic conditions which facilitate the development of an array of pathologies which have metabolic and nutritional dysfunctions as the established or proposed etiological agents. The levels of certain micronutrients, such as the vitamins B12 and B9 (folic acid), and of some intermediary metabolites, such as homocysteine are being thought of as etiological factors and/or as biological markers of a group of alterations which affect the normal functioning of the nervous system with important reflexes upon cognitive performance. This study aims to investigate the influence of homocysteine, B12 vitamin and folic acid levels on the cognitive performance of the low income elderly population. This transversal study took place in Natal, Rio Grande do Norte State, Brazil, and involved 205 dwelling elderly people, users of the Programa de Saúde da Família, a public healthcare program, maintained by the city s health authorities. A multidimensional questionnaire was used to assess the socio-demographic aspects and the overall health and nutrition conditions. The cognitive performance was measured by the use of the Portuguese version of the Mini Mental State Exam (MMSE). The serum levels of homocysteine, B12 vitamin and folic acid were determined by chemiluminescence. The association between the socio-demographic and serum levels of Hcy, B12 vitamin and folic acid was determined by multiple linear regression. Serum levels higher than 13.5 μmol/l, indicative of hyperhomocysteinemia (HHcy), were found on 25.4% of the sample, being more prevalent in men (p<0.05). Deficitary levels of folic acid (<5ng/mol) and of B12 vitamin (<193 pg/ml) were found on 3.9% and 10.2% of the sample respectively. A negative correlation was found between cognitive performance with both age and HHcy and a positive correlation was found between cognitive performance and schooling. The isolated HHcy R2 values were an explanation to only 4% of the variance of the MMSE scores. However, when associated with schooling and age, this model explains about 25% of this association

Fatores de satisfação de empregados: um estudo com docentes de instituição de educação tecnológica

This Master of Science Thesis deals with investigating the factors affecting employees satisfaction studying the case of teachers on a technological education institution. It is surveyed teachers in a sample of size 42 out of 316. It is used a form that deploys a model of satisfaction antecedents factors comprised of work system, professional development, teaching activity, physical environment, pay, and problems management. The sample was found representative (χ2 test) based on genre, tenure, degrees, and age. The model for satisfaction with the institution presented a adjusted r2 > 0,80 and the main factors affecting it was found to be work system, professional development, and teaching activity. For the satisfaction with the career, the model results with a r2 > 0,70 and as main factors professional development, teaching activitiy and pay. The variables contribuition for the students education and use of suggestions were ones of the main variables appearing in the models. The results suggest an improvement in the model regarding the previous models used by Silva (2003) and Cruz Filho (2007) regarding model explicability of teacher satisfaction

Genetic parameter estimates and response to selection for weight and testicular traits in Nelore cattle

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fatores operacionais e cinética do processo fermentativo para otimização da produção de etanol em escala industrial

Pós-graduação em Microbiologia Agropecuária - FCAV

Estudo prospectivo do desenvolvimento biométrico de olhos com catarata congênita e do desenvolvimento

Pós-graduação em Pesquisa e Desenvolvimento (Biotecnologia Médica) - FMB

Hormonal contraceptive use before hCG remission does not increase the risk of gestational trophoblastic neoplasia following complete hydatidiform mole: a historical database review

To re-evaluate the safety of hormonal contraceptives (HC) after uterine evacuation of complete hydatidiform mole (CHM). Historical database review. Charing Cross Hospital Gestational Trophoblastic Disease Centre, London, United Kingdom. Two thousand four hundred and twenty-three women with CHM of whom 154 commenced HC while their human chorionic gonadotropin (hCG) was still elevated, followed between 2003 and 2012. We compared time to hCG remission between HC users and nonusers. The relationship between HC use and gestational trophoblastic neoplasia (GTN) development was assessed. The relationship between HC use and a high International Federation of Gynecology and Obstetrics (FIGO) risk score was determined. Time to hCG remission, risk of developing postmolar GTN and proportion of women with high FIGO risk score. No relationship was observed between HC use with mean time to hCG remission (HC users versus non-users: 12 weeks in both, P = 0.19), GTN development (HC users versus non-users: 20.1 and 16.7%, P = 0.26) or high-risk FIGO score (HC users versus nonusers: 0% and 8%, P = 0.15). Moreover, no association between HC and GTN development was found, even when an age-adjusted model was used (OR = 1.37, 95% CI 0.91-2.08, P = 0.13). The use of current HC is not associated with development of postmolar GTN or delayed time to hCG remission. Therefore, HC can be safely used to prevent a new conception following CHM regardless of hCG level. Non-concurrent cohort study to re-evaluate the safety of low dose HCs after uterine evacuation of CHM.

Gestão de riscos em projetos de inovação através da abordagem contingencial: análise conceitual e proposição de modelo estruturado para redução de incertezas em projetos complexos

A intensificação de atividades inovadoras nas organizações tem desencadeado o surgimento de projetos de alto risco e com determinado nível de complexidade e estimulado a busca por modelos que possam tornam gerenciável as incertezas e riscos destes projetos. Metodologias tradicionais já não são suficientes para asseguram o sucesso destes projetos. A premissa de que um conjunto de ferramentas e técnicas padronizadas possa ser aplicável a todos os tipos de projetos tem sido fortemente questionada, dadas às diferenças fundamentais existentes entre eles. Este artigo apresenta uma revisão e análise da literatura de gerenciamento de riscos projetos inovadores a partir de uma perspectiva contingencial. Foram levantados artigos nas bases de dados científicas considerando- se duas grandes vertentes: tipologia de projetos e metodologias para gerenciamento de riscos de projetos inovativos e complexos. Com base na análise crítica da literatura, realizou-se uma proposição de um modelo estruturado para o gerenciamento das incertezas e riscos de projetos inovativos e complexos

The stratigraphic record of the quaternary sea level fluctuations and the impact of the post-glacial sea level rise (Termination I) in the Adriatic basin (Mediterranean sea)

The modern stratigraphy of clastic continental margins is the result of the interaction between several geological processes acting on different time scales, among which sea level oscillations, sediment supply fluctuations and local tectonics are the main mechanisms. During the past three years my PhD was focused on understanding the impact of each of these process in the deposition of the central and northern Adriatic sedimentary successions, with the aim of reconstructing and quantifying the Late Quaternary eustatic fluctuations. In the last few decades, several Authors tried to quantify past eustatic fluctuations through the analysis of direct sea level indicators, among which drowned barrier-island deposits or coral reefs, or indirect methods, such as Oxygen isotope ratios (δ18O) or modeling simulations. Sea level curves, obtained from direct sea level indicators, record a composite signal, formed by the contribution of the global eustatic change and regional factors, as tectonic processes or glacial-isostatic rebound effects: the eustatic signal has to be obtained by removing the contribution of these other mechanisms. To obtain the most realistic sea level reconstructions it is important to quantify the tectonic regime of the central Adriatic margin. This result has been achieved integrating a numerical approach with the analysis of high-resolution seismic profiles. In detail, the subsidence trend obtained from the geohistory analysis and the backstripping of the borehole PRAD1.2 (the borehole PRAD1.2 is a 71 m continuous borehole drilled in -185 m of water depth, south of the Mid Adriatic Deep - MAD - during the European Project PROMESS 1, Profile Across Mediterranean Sedimentary Systems, Part 1), has been confirmed by the analysis of lowstand paleoshorelines and by benthic foraminifera associations investigated through the borehole. This work showed an evolution from inner-shelf environment, during Marine Isotopic Stage (MIS) 10, to upper-slope conditions, during MIS 2. Once the tectonic regime of the central Adriatic margin has been constrained, it is possible to investigate the impact of sea level and sediment supply fluctuations on the deposition of the Late Pleistocene-Holocene transgressive deposits. The Adriatic transgressive record (TST - Transgressive Systems Tract) is formed by three correlative sedimentary bodies, deposited in less then 14 kyr since the Last Glacial Maximum (LGM); in particular: along the central Adriatic shelf and in the adjacent slope basin the TST is formed by marine units, while along the northern Adriatic shelf the TST is represented by costal deposits in a backstepping configuration. The central Adriatic margin, characterized by a thick transgressive sedimentary succession, is the ideal site to investigate the impact of late Pleistocene climatic and eustatic fluctuations, among which Meltwater Pulses 1A and 1B and the Younger Dryas cold event. The central Adriatic TST is formed by a tripartite deposit bounded by two regional unconformities. In particular, the middle TST unit includes two prograding wedges, deposited in the interval between the two Meltwater Pulse events, as highlighted by several 14C age estimates, and likely recorded the Younger Dryas cold interval. Modeling simulations, obtained with the two coupled models HydroTrend 3.0 and 2D-Sedflux 1.0C (developed by the Community Surface Dynamics Modeling System - CSDMS), integrated by the analysis of high resolution seismic profiles and core samples, indicate that: 1 - the prograding middle TST unit, deposited during the Younger Dryas, was formed as a consequence of an increase in sediment flux, likely connected to a decline in vegetation cover in the catchment area due to the establishment of sub glacial arid conditions; 2 - the two-stage prograding geometry was the consequence of a sea level still-stand (or possibly a fall) during the Younger Dryas event. The northern Adriatic margin, characterized by a broad and gentle shelf (350 km wide with a low angle plunge of 0.02° to the SE), is the ideal site to quantify the timing of each steps of the post LGM sea level rise. The modern shelf is characterized by sandy deposits of barrier-island systems in a backstepping configuration, showing younger ages at progressively shallower depths, which recorded the step-wise nature of the last sea level rise. The age-depth model, obtained by dated samples of basal peat layers, is in good agreement with previous published sea level curves, and highlights the post-glacial eustatic trend. The interval corresponding to the Younger Dyas cold reversal, instead, is more complex: two coeval coastal deposits characterize the northern Adriatic shelf at very different water depths. Several explanations and different models can be attempted to explain this conundrum, but the problem remains still unsolved.

Rapid climate change during the Weichselian Lateglacial in Ireland: Chironomid-inferred summer temperatures from Fiddaun, Co. Galway

A lacustrine sediment core from Fiddaun, western Ireland was studied to reconstruct summer temperature changes during the Weichselian Lateglacial. This site is located close to the Atlantic Ocean; and so is potentially sensitive to climatic changes associated with changes in ocean circulation. The record, comprising the end of the Weichselian Pleniglacial to the early Holocene, was analysed for fossil chironomids, lithology, and oxygen and carbon isotopes in the sedimentary carbonates. These proxies clearly show rapid warming at the onset of the Lateglacial Interstadial, relatively high summer temperatures during the Interstadial, pronounced cooling during the Younger Dryas, and subsequent warming at the transition to the Holocene. Chironomid-inferred mean July air temperatures for the Interstadial are ~12.5–14.5 °C, ~7.5 °C for the Younger Dryas, and ~15.0 °C for the early Holocene. Furthermore, this research provides evidence for at least two cold events during the Interstadial. These more moderate temperature oscillations can be correlated to Greenland Interstadial events 1b and 1d, on the basis of the age-depth model for the Fiddaun sequence. Based on multiple proxies, the first cold oscillation (GI-1d) was the more severe of the two in Ireland.

Dementia severity of the care receiver predicts procoagulant response in Alzheimer caregivers

BACKGROUND: The procoagulant factor D-dimer has been shown to be associated with thrombus formation and degradation as seen with conditions such as myocardial infarction and unstable angina. Research has demonstrated that spousal dementia caregivers have elevated levels of D-dimer relative to their non-caregiving peers. OBJECTIVE: The objective of this study was to determine the relationship of basal level and laboratory stressor-induced concentration of D-dimer to severity of dementia in spousal care recipients. METHODS: Seventy-one elderly caregivers were compared with a comparison group of 37 non-caregivers (average age: 71 years). Clinical Dementia Rating (CDR), a global measure of dementia, was used to assess severity of spousal dementia. Plasma D-dimer was measured at baseline and in response to an acute speech stressor. RESULTS: Regression analysis revealed a significant positive association between severity of spousal dementia and caregiver D-dimer, both at baseline and in response to acute stress, while controlling for age. The model examined an exponential relationship, with D-dimer increasing progressively across the span of dementia stages. DISCUSSION: Dementia severity of the care recipient was associated with increasing hypercoagulability among elderly caregivers. Effect size estimates suggest that such D-dimer increases may have clinical implications, particularly among late-stage caregivers.

Distinguishing phenotypes of childhood wheeze and cough using latent class analysis

Airway disease in childhood comprises a heterogeneous group of disorders. Attempts to distinguish different phenotypes have generally considered few disease dimensions. The present study examines phenotypes of childhood wheeze and chronic cough, by fitting a statistical model to data representing multiple disease dimensions. From a population-based, longitudinal cohort study of 1,650 preschool children, 319 with parent-reported wheeze or chronic cough were included. Phenotypes were identified by latent class analysis using data on symptoms, skin-prick tests, lung function and airway responsiveness from two preschool surveys. These phenotypes were then compared with respect to outcome at school age. The model distinguished three phenotypes of wheeze and two phenotypes of chronic cough. Subsequent wheeze, chronic cough and inhaler use at school age differed clearly between the five phenotypes. The wheeze phenotypes shared features with previously described entities and partly reconciled discrepancies between existing sets of phenotype labels. This novel, multidimensional approach has the potential to identify clinically relevant phenotypes, not only in paediatric disorders but also in adult obstructive airway diseases, where phenotype definition is an equally important issue.