Diffusion and Contagion in Networks with Heterogeneous Agents and Homophily

We study how a behavior (an idea, buying a product, having a disease, adopting a cultural fad or a technology) spreads among agents in an a social network that exhibits segregation or homophily (the tendency of agents to associate with others similar to themselves). Individuals are distinguished by their types (e.g., race, gender, age, wealth, religion, profession, etc.) which, together with biased interaction patterns, induce heterogeneous rates of adoption. We identify the conditions under which a behavior diffuses and becomes persistent in the population. These conditions relate to the level of homophily in a society, the underlying proclivities of various types for adoption or infection, as well as how each type interacts with its own type. In particular, we show that homophily can facilitate diffusion from a small initial seed of adopters.Comment: 18 pages, 1 figur

Diffusion and contagion in networks with heterogeneous agents and homophily

We study how a behavior (an idea, buying a product, having a disease, adopting a cultural fad or a technology) spreads among agents in an a social network that exhibits segregation or homophily (the tendency of agents to associate with others similar to themselves). Individuals are distinguished by their types (e.g., race, gender, age, wealth, religion, profession, etc.) which, together with biased interaction patterns, induce heterogeneous rates of adoption. We identify the conditions under which a behavior diffuses and becomes persistent in the population. These conditions relate to the level of homophily in a society, the underlying proclivities of various types for adoption or infection, as well as how each type interacts with its own type. In particular, we show that homophily can facilitate diffusion from a small initial seed of adopters.Diffusion, Homophily, Segregation, Social Networks

A probable pre-main sequence chemically peculiar star in the open cluster Stock 16

We used the Ultraviolet and Visual Echelle Spectrograph of the ESO-Very Large Telescope to obtain a high resolution and high signal-to-noise ratio spectrum of Stock 16-12, an early-type star which previous Delta-a photometric observations suggest being a chemically peculiar (CP) star. We used spectral synthesis to perform a detailed abundance analysis obtaining an effective temperature of 8400 +/- 400 K, a surface gravity of 4.1 +/- 0.4, a microturbulence velocity of 3.4 +0.7/-0.3 km/s, and a projected rotational velocity of 68 +/- 4 km/s. We provide photometric and spectroscopic evidence showing the star is most likely a member of the young Stock 16 open cluster (age 3-8 Myr). The probable cluster membership, the star's position in the Hertzsprung-Russell diagram, and the found infrared excess strongly suggest the star is still in the pre-main-sequence (PMS) phase. We used PMS evolutionary tracks to determine the stellar mass, which ranges between 1.95 and 2.3 Msun, depending upon the adopted spectroscopic or photometric data results. Similarly, we obtained a stellar age ranging between 4 and 6 Myr, in agreement with that of the cluster. Because the star's chemical abundance pattern resembles well that known of main sequence CP metallic line (Am) stars, the object sets important constraints to the diffusion theory. Additional spectroscopic and spectropolarimetric data allowed us to conclude that the object is probably a single non-magnetic star.Comment: Accepted for publication in MNRAS; 8 pages, 5 figures, 1 tabl

The spectral type of CHS7797 - an intriguing very low mass periodic variable in the Orion Nebula Cluster

We present the spectroscopic characterization of the unusual high-amplitude very low mass pre-main-sequence periodic variable CHS7797. This study is based on optical medium-resolution (R=2200) spectroscopy in the 6450-8600 A range, carried out with GMOS-GEMINI-S in March 2011. Observations of CHS7797 have been carried out at two distinct phases of the 17.8d period, namely at maximum and four days before maximum. Four different spectral indices were used for the spectral classification at these two phases, all of them well-suited for spectral classification of young and obscured late M dwarfs. In addition, the gravity-sensitive NaI (8183/8195 A) and KI (7665/7699 A) doublet lines were used to confirm the young age of CHS7797. From the spectrum obtained at maximum light we derived a spectral type (SpT) of M6.05, while for the spectrum taken four days before maximum the derived SpT is M5.75. The derived SpTs confirm that CHS7797 has a mass in the stellar-substellar boundary mass range. In addition, the small differences in the derived SpTs at the two observed phases may provide indirect hints that CHS7797 is a binary system of similar mass components surrounded by a tilted circumbinary disk, a system similar to KH15D.Comment: 6 pages, accepted for publication A&

Atmospheric pressure gas chromatography-time-of-flight-mass spectrometry (APGC-ToF-MS) for the determination of regulated and emerging contaminants in aqueous samples after stir bar sorptive extraction (SBSE)

This work presents the development, optimization and validation of a multi-residue method for the simultaneous determination of 102 contaminants, including fragrances, UV filters, repellents, endocrine disruptors, biocides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and several types of pesticides in aqueous matrices. Water samples were processed using stir bar sorptive extraction (SBSE) after the optimization of several parameters: agitation time, ionic strength, presence of organic modifiers, pH, and volume of the derivatizing agent. Target compounds were extracted from the bars by liquid desorption (LD). Separation, identification and quantification of analytes were carried out by gas chromatography (GC) coupled to time-of-flight (ToF-MS) mass spectrometry. A new ionization source, atmospheric pressure gas chromatography (APGC), was tested. The optimized protocol showed acceptable recovery percentages (50–100%) and limits of detection below 1 ng L−1 for most of the compounds. Occurrence of 21 out of 102 analytes was confirmed in several environmental aquatic matrices, including seawater, sewage effluent, river water and groundwater. Non-target compounds such as organophosphorus flame retardants were also identified in real samples by accurate mass measurement of their molecular ions using GC-APGC–ToF-MS. To the best of our knowledge, this is the first time that this technique has been applied for the analysis of contaminants in aquatic systems. By employing lower energy than the more widely used electron impact ionization (EI), AGPC provides significant advantages over EI for those substances very susceptible to high fragmentation (e.g., fragrances, pyrethroids)

Microbiological, biochemical and biogenic amine profiles of Terrincho cheese manufactured in several dairy farms

Terrincho is a Portuguese traditional cheese, bearing a protected denomination of origin (PDO) status, which is manufactured from raw ewes’ milk and ripened for a minimum period of 30 d. The objectives of this research effort were to characterize the microbiological and biochemical profiles of this cheese, manufactured in several dairy farms during the winter cheesemaking season (December through March), and establish tentative correlations between these profiles and formation of biogenic amines. For this goal, 29 cheeses from five batches, manufactured in as many dairy farms located throughout the PDO region, were analysed. The viable numbers of the total (mesophilic) microflora, enterococci, lactococci, lactobacilli, enterobacteria, staphylococci, pseudomonads, yeasts and moulds were determined by 30 d, following classical plate counting on specific media. Free amino acid and biogenic amine contents were determined by reverse-phase high-pressure liquid chromatography. The concentration of biogenic amines correlated well with microbial viable numbers, in both qualitative and quantitative terms; significant correlations were observed between enterococci and phenylethylamine (r ¼ 0.868, po0.0001), and between lactococci and cadaverine (r = 0.646, p <0.002) and tyramine (r = 0.868, p<0.0001). On the other hand, 220 g of Terrincho cheese would have to be consumed at a given time if the threshold of worst case risk was to be attained, which appears unrealistic for a typically single-doses meal ingredient. This study has contributed to deepen the knowledge on the microbiological and biochemical features of a unique Portuguese cheese throughout ripening, and to rationalize its safe consumption in terms of biogenic amines

Desidratação osmótica de pêssego com calda açucarada e calda à base de mel.

Comunicação da qual só está disponível o resumo.A desidratação é um processo que consiste na eliminação de água de um produto por evaporação. Com o aumento da produção e sazonalidade de diversos frutos a produção de fruta desidratada pode ser uma alternativa para escoamento dos excedentes. Os produtos alimentares podem ser desidratados por processos baseados na vaporização, sublimação, remoção de água por solventes ou na adição de agentes osmóticos. Nos últimos anos, a desidratação de alimentos tem sido objeto de vários estudos no sentido de produzir alimentos desidratados, que conservem ou melhorem as características sensoriais e valor nutricional, garantindo um custo adequado. Este trabalho teve como objetivo avaliar os parâmetros de qualidade de rodelas de pêssego submetidas a desidratação osmótica utilizando dois tipos de caldas. Numa fase inicial foram realizados vários ensaios a fim de selecionar um programa de secagem adequado, que não proporcionasse alteração significativa da cor da fruta (determinado por colorímetro no sistema CIELAB), fosse adequado do ponto de vista microbiológico e tivesse a preferência dos provadores na avaliação sensorial. O programa de secagem selecionado tem a duração de 12 horas: 30 min até atingir a temperatura de 520C; 10,5 horas à temperatura de 520C; 1 hora para estabilização. De seguida foram testadas 4 caldas: calda açucarada com três concentrações diferentes de frutose (C1: 365 g/L, C2: 490 g/L e C3: 735 g/L) e uma calda à base de mel (diluição de 1:1 m/v); para desidratação osmótica seguida de secagem. Este programa de secagem teve a duração de 10 horas. Para estas 4 amostras foi efetuada uma prova de ordenação tendo a amostra C3 (735 g/L de frutose) obtido a maior pontuação. Para as amostras selecionadas de secagem simples e secagem com pré-tratamento de desidratação osmótica foram efetuadas as seguintes determinações: humidade (PT.LFQ.0135-Método interno); gordura (AOAC 2003.06); proteína (PT.LFQ.0105-Método interno); cinzas (AOAC 934.03); hidratos de carbono (cálculo); valor energético (cálculo); sódio (ICP-OES); sal (cálculo); glucose; frutose; sacarose; maltose; lactose (PT.LFQ.0129-Método interno). Os resultados demonstraram que o produto com pré-tratamento, embora mais apreciados pelos provadores apresenta um teor de açúcares (frutose) superior, inerente ao tratamento e um teor de humidade, gordura e proteína inferior. É de referir, no entanto, que este trabalho deve ser continuado de modo a aferir as melhores condições para a secagem após a desidratação osmótica (especialmente para a calda de mel) dado que os provadores gostaram do sabor da amostra tratada com mel mas pontuaram pior devido à elevada gomosidade que apresentava.info:eu-repo/semantics/publishedVersio

Iron complexation using spent yeast peptides for human supplementation

info:eu-repo/semantics/publishedVersio

Novel, edible melanin-protein-based bioactive films for cheeses: antimicrobial, mechanical and chemical characteristics

The cheese rind is the natural food packaging of cheese and is subject to a wide range of external factors that compromise the appearance of the cheese, including color defects caused by spoilage microorganisms. First, eight films based on whey protein isolate (WPI) coatings were studied, of which IS3CA (WPI 5% + sorbitol 3% + citric acid 3%) was selected for presenting better properties. From the IS3CA film, novel films containing melanin M1 (74 g/mL) and M2 (500 g/mL) were developed and applied to cheese under proof-of-concept and industrial conditions. After 40 days of maturation, M2 presented the lowest microorganism count for all the microbial parameters analyzed. The cheese with M2 showed the lowest lightness, which indicates that it is the darkest cheese due to the melanin concentration. It was found that the mechanical and colorimetric properties are the ones that contribute the most to the distinction of the M2 film in cheese from the others. Using FTIR-ATR, it was possible to distinguish the rinds of M2 cheeses because they contained the highest concentrations of melanin. Thus, this study shows that the film with M2 showed the best mechanical, chemical and antimicrobial properties for application in cheese.This work was financially supported by Fundação para a Ciência e Tecnologia (FCT) with financial support from IPCB-CERNAS (UID/AMB/00681/2020) Research Unit Grant from FCT, and from UIDB/00239/2020 (CEF). Work was supported by UIDB/04046/2020 and UIDP/04046/2020 Centre grants from FCT, Portugal (to BioISI). The work was co-funded by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. This work is the recipient of a project (PTDC/Bia- BQM/28355/2017) grant, and Ana Rita Ferraz acknowledges a Ph.D. fellowship (SFRH/BD/135692/2018) from FCT (Portugal).info:eu-repo/semantics/publishedVersio

Sensory evaluation of virgin olive oils from organic agriculture and integrated production

In the present work four olive groves were selected: two in organic agriculture and two in integrated production. Olives were handpicked at two ripening stages and processed by a low-scale mill with a working capacity of 0.05 tons h-1. Differences between olive oils were evaluated through a sensory quantitative descriptive analysis (QDA) for positive attributes; moreover, some chemical parameters that could be related with bitterness, like phenol content and the specific absorbance at 225 nm (K225), were determined as well. Some analyses were also conducted with an Alpha MOS electronic nose system, FOX 2000