The Euler characteristic as a topological marker for outbreaks in vector-borne disease

Abstract. Epidemic outbreaks represent a significant concern for the current state of global health, particularly in Brazil, the epicentre of several vector-borne disease outbreaks and where epidemic control is still a challenge for the scientific community. Data science techniques applied to epidemics are usually made via standard statistical and modelling approaches, which do not always lead to reli- able predictions, especially when the data lacks a piece of reliable surveillance information needed for precise parameter estimation. In particular, dengue out- breaks reported over the past years raise concerns for global health care, and thus novel data-driven methods are necessary to predict the emergence of out- breaks. In this work, we propose a parameter-free approach based on geometric and topological techniques, which extracts geometrical and topological invariants as opposed to statistical summaries used in established methods. Specifically, our procedure generates a time-varying network from a time-series of new epidemic cases based on synthetic time-series and real dengue data across several dis- tricts of Recife, the fourth-largest urban area in Brazil. Subsequently, we use the Euler characteristic (EC) to extract key topological invariant of the epidemic time-varying network and we finally compared the results with the effective reproduction number (Rt) for each data set. Our results unveil a strong cor- relation between epidemic outbreaks and the EC. In fact, sudden changes in the EC curve preceding and/or during an epidemic period emerge as a warn- ing sign for an outbreak in the synthetic data, the EC transitions occur close to the periods of epidemic transitions, which is also corroborated. In the real dengue data, where data is intrinsically noise, the EC seems to show a better sign-to-noise ratio once compared to Rt. In analogy with later studies on noisy data by using EC in positron emission tomography scans, the EC estimates the number of regions with high connectivity in the epidemic network and thus has potential to be a signature of the emergence of an epidemic state. Our results open the door to the development of alternative/complementary topological and geometrical data-driven methods to characterise vector-borne disease outbreaks, specially when the conventional epidemic surveillance methods are not effective in a scenario of extreme noise and lack of robustness in the data

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments : comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

Further advances inmagnetic hyperthermiamight be limited by biological constraints, such as using sufficiently low frequencies and low field amplitudes to inhibit harmfuleddy currents inside the patient’s body. These incite the need to optimize the heatingefficiency of the nano particles, referred to as the specific absorption rate (SAR).Among the several properties currently under research, one of particular importance is the transition from the linear to the non-linear regime that takes place as the field amplitude is increased, an aspect where the magnetic anisotropy is expected to play a fundamental role. In this paper we investigate the heating properties of cobalt ferrite and maghemite nano particles under the influence of a 500 kHz sinusoidal magneticfield with varying amplitude, up to 134 Oe. The particles were characterized byTEM, XRD, FMR and VSM, from which most relevant morphological, structural and magnetic properties were inferred. Both materials have similar size distributions and saturation magnetization, but strikingly different magnetic anisotropies. Frommagnetic hyperthermia experiments we found that, while at low fields maghemiteis the best nanomaterial for hyperthermia applications, above a critical field, close to the transition from the linear to the non-linear regime, cobalt ferrite becomesmore efficient. The results were also analyzed with respect to the energy conversionefficiency and compared with dynamic hysteresis simulations. Additional analysiswith nickel, zinc and copper-ferrite nanoparticles of similar sizes confirmed the importance of the magnetic anisotropy and the damping factor. Further, the analysis of the characterization parameters suggested core-shell nanostructures, probably due to a surface passivation process during the nanoparticle synthesis. Finally, we discussed the effect of particle-particle interactions and its consequences, in particular regarding discrepancies between estimated parameters and expected theoretical predictions

Anemia em escolares da primeira série do ensino fundamental da rede pública de Maceió, Alagoas, Brasil Anemia in public school first graders in the city of Maceió, Alagoas, Brazil

Realizou-se um estudo transversal com amostra probabilística de 426 alunos de 6 a 10 anos, da 1ª série do ensino fundamental das escolas públicas de Maceió, Alagoas, Brasil. O objetivo foi avaliar a prevalência da anemia e sua associação com o retardo de crescimento. Os dados foram coletados entre maio e julho de 2000. O sangue foi colhido por venipuntura e a dosagem de hemoglobina (Hb) foi realizada pelo contador Coulter STKS. Classificou-se a anemia por dois critérios estabelecidos pela Organização Mundial da Saúde: Hb <11,5g/dl e Hb <12,0g/dl. O retardo pondo-estatural foi diagnosticado quando os indicadores Altura/Idade (A/I), Peso/Idade (P/I) e Peso/Altura (P/A) se encontravam abaixo de -2,0 desvios-padrão da referência NCHS. A prevalência da anemia foi de 9,9%, considerando-se Hb <11,5g/dl e de 25,4%, utilizando-se Hb <12,0g/dl. O retardo do crescimento foi detectado em 6,2% segundo A/I, 4,0% pelo indicador P/I e 3,0% em relação a P/A. Não houve associação estatisticamente significativa entre as variáveis do estudo. Estes resultados confirmam os observados em outras pesquisas: prevalência de anemia muito superior à prevalência do retardo pondo-estatural. Conclui-se que as graves conseqüências da anemia nesta faixa etária, justificam a implementação de políticas de largo alcance para o enfrentamento do problema.<br>A cross-sectional study was conducted in a representative sample of 426 randomly selected first graders (ages 6 to 10 years) from public schools in Maceió, State of Alagoas, Brazil. The aim was to determine the prevalence of anemia, as well as its association with growth retardation. Data were collected from May to July 2000, and determination of hemoglobin (HGB) employed an STKS Coulter counter. Two cut-off points were used to classify anemia, both established by the World Health Organization: HGB < 11.5g/dl and HGB < 12.0g/dl. The indicators height/age (H/A), weight/age (W/A), and weight/height (W/H) below -2.0 standard deviations from the NCHS reference were diagnosed as growth retardation. Prevalence of anemia was 9.9% when HGB < 11.5g/dl was used, and 25.4% when the cut-off point was HGB < 12.0g/dl. Growth retardation was detected in 6.2% of children according to H/A, 4.0% for W/A, and 3.0% for W/H. There was no statistically significant association between the variables in the study. These findings confirm results of previous surveys where prevalence of anemia was much higher than that of growth retardation. The severe consequences of anemia in this age group justify the implementation of broad public policies to overcome this nutritional deficiency