Wave localization in strongly nonlinear Hertzian chains with mass defect

We investigate the dynamical response of a mass defect in a one-dimensional non-loaded horizontal chain of identical spheres which interact via the nonlinear Hertz potential. Our experiments show that the interaction of a solitary wave with a light intruder excites localized mode. In agreement with dimensional analysis, we find that the frequency of localized oscillations exceeds the incident wave frequency spectrum and nonlinearly depends on the size of the intruder and on the incident wave strength. The absence of tensile stress between grains allows some gaps to open, which in turn induce a significant enhancement of the oscillations amplitude. We performed numerical simulations that precisely describe our observations without any adjusting parameters.Comment: 4 pages, 5 figures, submitted for publicatio

Revegetação da área de contribuição e estabilização de voçorocas através de práticas mecânicas e vegetativas.

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Embrapa Tabuleiros Costeiros produz rebanho de ovelhas Santa Inês com maior prolificidade.

Apesar do crescimento e do reconhecido valor sócio-econômico da atividade, a ovinocultura brasileira ainda apresenta, em muitos casos, reduzidos índices de produtividade em conseqüência do baixo desempenho reprodutivo e produtivo dos rebanhos. Entende-se como eficiência reprodutiva a somatória da fertilidade, da prolificidade e da sobrevivência dos cordeiros no sistema de produção. O número de cordeiros nascidos por ovelha acasalada é resultado da fertilidade e da prolificidade, e a sobrevivência desses cordeiros está principalmente na dependência da alimentação pré-parto, da habilidade materna e do manejo adequado da mãe e do cordeiro pós-parto. A otimização da eficiência reprodutiva depende do uso de melhores condições alimentares e de raças, cruzamentos ou animais mais eficientes para a produção sendo que a genética e a alimentação são as bases fundamentais do sistema tendo reflexo direto sobre a reprodução e podendo comprometer o seu desempenho (Pilar et al., 2002).bitstream/item/123112/1/Embrapa-Tabuleiros.pd

Academic Achievement in Physics-Chemistry: The Predictive Effect of Attitudes and Reasoning Abilities

Science education plays a critical role as political priority due to its fundamental importance in engaging students to pursue technological careers considered essential in modern societies, in order to face scientific development challenges. High-level achievement on science education and positive attitudes toward science constitutes a crucial challenge for formal education. Several studies indicate close relationships between students’ attitudes, cognitive abilities, and academic achievement. The main purpose of this study is to analyze the impact of student’s attitudes toward the school discipline of Physics and Chemistry and their reasoning abilities on academic achievement on that school subject, among Portuguese 9th grade students using the data collected during the Project Academic Performance and Development: a longitudinal study on the effects of school transitions in Portuguese students (PTDC/CPE-CED/104884/2008). The participants were 470 students (267 girls – 56.8% and 203 boys – 43.2%), aged 14–16 years old (m D 14.3 0.58). The attitude data were collected using the Attitude toward Physics-Chemistry Questionnaire (ATPCQ) and, the Reasoning Test Battery (RTB) was used to assess the students reasoning abilities. Achievement was measured using the students’ quarterly (9-week) grades in the physics and chemistry subject. The relationships between the attitude dimensions toward Physics-chemistry and the reasoning dimensions and achievement in each of the three school terms were assessed by multiple regression stepwise analyses and standardized regression coefficients (b), calculated with IBM SPSS Statistics 21 software. Both variables studied proved to be significant predictor variables of school achievement. The models obtained from the use of both variables were always stronger accounting for higher proportions of student’s grade variations. The results show that ATPCQ and RTB had a significantly positive relationship with student’s achievement in Physics-chemistry, indicating that both attitudinal and cognitive variables should be taken into account on science education as well as in educative intervention

Iron, copper and manganese complexes with in vitro superoxide dismutase and/or catalase activities that keep Saccharomyces cerevisiae cells alive under severe oxidative stress

Due to their aerobic lifestyle, eukaryotic organisms have evolved different strategies to overcome oxidative stress. The recruitment of some specific metalloenzymes such as superoxide dismutases (SODs) and catalases (CATs) is of great importance for eliminating harmful reactive oxygen species (hydrogen peroxide and superoxide anion). Using the ligand HPCINOL {1-[bis(pyridin-2-ylmethyl)amino]-3-chloropropan-2-ol}, we have synthesized three coordination compounds containing iron(III), copper(II), and manganese(II) ions, which are also present in the active site of the above-noted metalloenzymes. These compounds were evaluated as SOD and CAT mimetics. The manganese and iron compounds showed both SOD and CAT activities, while copper showed only SOD activity. The copper and manganese in vitro SOD activities are very similar (IC50 similar to 0.4 mu mol dm(-3)) and about 70-fold higher than those of iron. The manganese compound showed CAT activity higher than that of the iron species. Analyzing their capacity to protect Saccharomyces cerevisiae cells against oxidative stress (H2O2 and the O-2(center dot-) radical), we observed that all compounds act as antioxidants, increasing the resistance of yeast cells mainly due to a reduction of lipid oxidation. Especially for the iron compound, the data indicate complete protection when wild-type cells were exposed to H2O2 or O-2(center dot-) species. Interestingly, these compounds also compensate for both superoxide dismutase and catalase deficiencies; their antioxidant activity is metal ion dependent, in the order iron(III) > copper(II) > manganese(II). The protection mechanism employed by the complexes proved to be independent of the activation of transcription factors (such as Yap1, Hsf1, Msn2/Msn4) and protein synthesis. There is no direct relation between the in vitro and the in vivo antioxidant activities. (C) 2014 Elsevier Inc. All rights reserved

Prevalência de resistência antimicrobiana e características de virulência em Salmonella spp. isoladas de alimentos associados ou não com salmonelose no Brasil

Salmonella é o agente etiológico mais comumente envolvido em casos e surtos de doenças diarréicas de origem alimentar. A preocupação com este patógeno é, ainda, maior quando se verifica o surgimento e a disseminação de cepas multirresistentes e potencialmente mais patogênicas. Neste estudo, 237 cepas Salmonella spp., associadas ou não com casos ou surtos de salmonelose e pertencentes, principalmente, ao sorovar Enteritidis, foram avaliadas quanto ao perfil de susceptibilidade antimicrobiana e presença dos genes de virulência spvC, invA, sefA e pefA. Entre as cepas avaliadas, 46,8% foram sensíveis a todos os agentes antimicrobianos e 51,9% foram resistentes a pelo menos uma droga. Multirresistência foi observada em 10,5% das cepas. As maiores taxas de resistência foram observadas para estreptomicina (35,9%) e ácido nalidíxico (16,9%). Não foram detectadas cepas resistentes à cefoxitina, cefalotina, cefotaxima, amicacina, ciprofloxaxina e imipenem. O gene invA foi detectado em todas as cepas de Salmonella. Os genes spvC e pefA foram encontrados em 48,1% e 44,3% das cepas, respectivamente. O gene sefA foi detectado em 31,6% das cepas, estando presente somente entre as cepas de S. Enteritidis. Resistência antimicrobiana e marcadores de virulência foram detectados em cepas de Salmonella pertencentes a diversos sorovares. A alta taxa de resistência antimicrobiana verificada em cepas isoladas de frangos e derivados demonstra o potencial risco associado ao consumo destes produtos e a necessidade de se assegurar boas práticas de higiene em toda cadeia produtiva para reduzir a disseminação de patógenos relevantes para a saúde pública.Salmonella is the most common etiological agent of cases and outbreaks of foodborne diarrheal illnesses. The emergence and spread of Salmonella spp., which has become multi-drug resistant and potentially more pathogenic, have increased the concern with this pathogen. In this study, 237 Salmonella spp., associated or not with foodborne salmonellosis in Brazil, belonging mainly to serotype Enteritidis, were tested for antimicrobial susceptibility and the presence of the virulence genes spvC, invA, sefA and pefA. Of the isolates, 46.8% were sensitive to all antimicrobials and 51.9% were resistant to at least one antimicrobial agent. Resistance to more than one antimicrobial agent was observed in 10.5% of the strains. The highest rates of resistance were observed for streptomycin (35.9%) and nalidixic acid (16.9%). No strain was resistant to cefoxitin, cephalothin, cefotaxime, amikacin, ciprofloxacin and imipenem. The invA gene was detected in all strains. Genes spvC and pefA were found in 48.1% and 44.3% of strains, respectively. The gene sefA was detected in 31.6% of the strains and only among S. Enteritidis. Resistance and virulence determinants were detected in Salmonella strains belonging to several serotypes. The high rates of antibiotic-resistance in strains isolated from poultry products demonstrate the potential risk associated with the consumption of these products and the need to ensure good food hygiene practices from farm to table to reduce the spread of pathogens relevant to public health

Fitointoxicação causada por deriva de Glyphosate em soja convencional.

Para simular as conseqüências da deriva de glyphosate na soja convencional. BRS 232, foram conduzidos cinco experimentos, em Londrina, PR. Brasil. Os tratamentos contemplaram doses isoladas do herbicida e em mistura com sulfato de manganês. Estas doses correspondem à volumes que variaram de 0,6% a 38% da dose comumente indicada na soja resistente. Os resultados mostraram desde leve clorose até a morte de plantas na dose mais alta. Houve acúmulo de ácido chiquímico nas plantas tratadas com glifosate, tanto nos foliolos desenvolvidos como em desenvolvimento, sendo que nesse caso. esse acúmulo ocorreu no intervalo entre 1 e 10 dias após aplicação dos tratamentos (DAT). Apos 30 DAT, os níveis de ácido chiquímico retomaram ao normal, não diferindo significativamente daqueles observados nas plantas testemunha. Perdas de rendimento foram observadas a partir de 0,48 I de glyphosate p.c. ha-1 (0.31 g.La.ha-\ sugerindo que. caso ocorra deriva deste produto para lavouras de soja convencional a eliminação não é necessária na maioria dos casos, pois a cultura tem condições de se recuperar