Mathematical hybrid models for image segmentation.

Two hybrid image segmentation models that are able to process a wide variety of images are proposed. The models take advantage of global (region) and local (edge) data of the image to be segmented. The first one is a region-based PDE model that incorporates a combination of global and local statistics. The influence of each statistic is controlled using weights obtained via an asymptotically stable exponential function. Through incorporation of edge information, the second model extends the capabilities of a strictly region-based variational formulation, making it able to process more general images. Several examples are provided showing the improvements of the proposed models over recent methods along with an application to dermoscopy imaging. A number of avenues for future research are also discussed

Improvement and analysis of a pseudo random bit generator by means of cellular automata

In this paper, we implement a revised pseudo random bit generator based on a rule-90 cellular automaton. For this purpose, we introduce a sequence matrix H_N with the aim of calculating the pseudo random sequences of N bits employing the algorithm related to the automaton backward evolution. In addition, a multifractal structure of the matrix H_N is revealed and quantified according to the multifractal formalism. The latter analysis could help to disentangle what kind of automaton rule is used in the randomization process and therefore it could be useful in cryptanalysis. Moreover, the conditions are found under which this pseudo random generator passes all the statistical tests provided by the National Institute of Standards and Technology (NIST)Comment: 20 pages, 12 figure

A Comparison of Individual Versus Community Influences on Youth Smoking Behaviours: A Cross-Sectional Observational Study

Objectives: To compare individual with community risk factors for adolescent smoking. Design: A cross-sectional observational study with multivariate analysis.Setting: National telephone survey.Participants: 3646 US adolescents aged 13–18 years in 2007 recruited through a random digit-dial survey

Efecto de la fertilización y época de corte de las paniculas sobre la producción de semilla de pasto Guinea (Panicum maximum Jacq.)

En el Centro Experimental Nataima, localizado en el municipio de Espinal, Tolima, temperatura media de 27 C. precipitación promedia anual de 1.551,9 mm y altura de 385 m.s.n.m., se efectuó un ensayo de campo con el objeto de determinar el efecto de Ia fertilización con N, P y K y época de corte de las panículas sobre Ia producción de semilla de pasto guinea (Panicum maximum Jacq.). Se observó que el intervalo entre cortes y dosis de N afectaron significativamente tanto Ia producción total de semillas como Ia mayoría de los componentes del rendimiento. Los rendimientos en semilla desgranada y sin desgranar (peso fresco), número de macollas y panículas por planta y peso de semilla por panícula. se afectaron en forma altamente significativa según Ia frecuencia en los cortes de Ia panícula y las diferentes dosis de N. La fertilización con P y K no fue significativa para ninguna de [as evaluaciones mencionadas. De acuerdo a las regresiones y correlaciones se deduce que los factores que más contribuyeron al rendimiento fueron el número de macollas y el número de panículas por planta y que éstas a su vez presentaron una correlación altamente significativa con el peso de semilla llena por panícula.A field experiment was conducted to study the effect of N, P and K fertilization and time of cutting of the panicle, on seed production of guinea grass. Panicum maximum Jacq., the trial was conducted at Nataima Agricultural Experiment Station in Espinal, Tohma, with a mean temperature of 27°C, 1.552 mm of precipitation and 385 meters of altitude. The data obtained showed that cut interval and N fertilization significatively affected total seed production as well as the mejority of yield components. It was observed that the shelling and non shelling seed production (fresh weight), number of panicles and stalks per plant and seed weight per panicle were highly significant affected by frecuency of cutting and N levels. Fertilization with P and K did not significantly affected the studied parameters. According to the regression and correlation analysis, it is concluded that the most contributing factors to seed yields were the number of bunch stalks and the number of panicles per plant. These two variables showed a highly significant correlation with seed weight per panicle.Ganado de doble propósito-Ganaderia doble proposit

Current in coherent quantum systems connected to mesoscopic Fermi reservoirs

We study particle current in a recently proposed model for coherent quantum transport. In this model, a system connected to mesoscopic Fermi reservoirs (meso-reservoir) is driven out of equilibrium by the action of super-reservoirs thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. We compare exact (numerical) results with theoretical expectations based on the Landauer formula

Factors associated with producing a scientific publication during medical training: evidence from a cross-sectional study of 40 medical schools in Latin America [version 2; peer review: 2 approved]

"Background: Scientific publication during medical training is key to promoting enduring cutting-edge knowledge. The promotion of science among medical students in Latin America is a multisectoral issue that is hampered by the lack of governmental knowledge to invest in national research, as well as by the lack of support from local universities. This study aims to determine the factors associated with the production of a scientific publication during medical training among Latin American medical students of local scientific societies. Methods: This is a secondary data analysis of a cross-sectional study conducted in 2016 that assessed the use of information and communication technologies (ICTs) among medical students from 40 local scientific societies of medical students affiliated with FELSOCEM. Teams from each local scientific society surveyed self-reported scientific publications and explored their association with socioeconomic, academic, and research training conditions. We applied nested models to identify the covariates associated with selfreported scientific publication, obtaining a parsimonious mixedeffects multilevel model grouped by medical scientific society. Results: Of 11,587 participants, the prevalence of scientific publications increased in 36% among medical students affiliated to a Scientific Society of Medical Students [parsimonious prevalence ratio (pPR)=1.36, 95%CI=1.16–1.59], 51% among medical students with advanced English proficiency [pPR=1.51, 95%CI=1.21 – 1.87], 85% among medical students who attended a scientific writing skills course [pPR=1.85, 95%CI=1.59–2.15], 81% among medical students who use Sci-Hub [pPR=1.81, 95%CI=1.50–2.20], and 108% among medical students who have access to a pirated academic account [pPR=2.08, 95%CI=1.83–2.36]. Conclusions: Producing a scientific publication among medical students is associated with being affiliated to a scientific society of medical students, English proficiency, training in scientific writing, use of Sci-Hub, and pirated academic accounts. The results will help clinical educators and medical programs improve resources for training students in high-quality research

Impact in hospitalization costs of a cardiovascular risk management program in Colombia: a propensity score matching model

Cardiovascular diseases (CVD) are the leading cause of death and burden of disease in Colombia and globally. In 2017, CVD represented the 12% of total DALYs. CVD is a costly disease from patient, family and societal perspectives. Effective prevention and risk management programs reduces the incidence of CVD by as much as 80%. We aimed to estimate the impact of direct medical hospitalization costs related to adherence in a risk management program in Colombia, 2018. We retrospectively collected data from 6,243 patients with data of enrollment in a cardiovascular risk management program (DTC, in Spanish) of a subsidized insurer, who presented arterial hypertension (AH) or AH+ type 2 diabetes mellitus (DM2). 1,065 were identified adherent to the program (treated) and 5.178 non adherent (controls). We designed a propensity score matching model adjusted with confounding variables to estimate the effect of treatment (program adherence) over hospitalization cost. Costs were calculated based on hospitalization invoices and expressed in Colombian pesos (COP) 2018. DTC has an average negative effect on cost of treated population. Being treated avoids hospitalization costs; these results were statistically significant at the 5% and 10% level (with 95%CI that goes through zero). Hence, being in the DTC program reduces hospital costs that ranges from COP-$11,346,372 to -$ 799,259 (95%CI) compared to the average cost. The overall impact on program costs is a significant saving of COP583,670 per event-year. If all members of the DTC program fulfilled its activities by more than 80%, the savings generated by the program would be close to COP$ 6.85 billion. DTC risk management program reduces direct hospitalization costs of events associated to CVD. Our results are important to design policies focused on the cost and risk management of patients with CVD in poor population