Ranking and clustering of nodes in networks with smart teleportation

Random teleportation is a necessary evil for ranking and clustering directed networks based on random walks. Teleportation enables ergodic solutions, but the solutions must necessarily depend on the exact implementation and parametrization of the teleportation. For example, in the commonly used PageRank algorithm, the teleportation rate must trade off a heavily biased solution with a uniform solution. Here we show that teleportation to links rather than nodes enables a much smoother trade-off and effectively more robust results. We also show that, by not recording the teleportation steps of the random walker, we can further reduce the effect of teleportation with dramatic effects on clustering.Comment: 10 pages, 7 figure

No-horizon theorem for spacetimes with spacelike G1 isometry groups

We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike $G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on ${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent horizons. Given any (3+1) spacetime with spacelike translational isometry, the no-horizon condition can be readily tested without the need for dimensional reduction. This provides thus a useful and encompassing apparent horizon test for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence towards the validity of the hoop conjecture, and signals possible violations of strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra

A closer look at the U(1)B−LU(1)_{B-L} explanation of the ATOMKI nuclear anomalies

We revisit the gauged $U(1)_{B-L}$ explanation of the ATOMKI nuclear anomalies, in which the new gauge boson is the hypothetical $X(17)$ particle. It is known that the vanilla $B-L$ scenario is unable to account for appropriate couplings, namely the suppression of the couplings of $X(17)$ to neutrinos, which motivates adding vector-like leptons. The simplest case, in which the new fields have $B-L$ charges equal to $1$, is highly disfavoured since it requires large mixing with the Standard Model fields. One solution recently put forward is to consider large $B-L$ charges to counterbalance small mixing. We show that, in this scenario, and after taking into account several phenomenological constraints, the dominant contribution to the muon anomalous magnetic moment $(g-2)_\mu$ is expected to be extremely large and with a negative sign, being thus excluded by experiment.Comment: 15 LaTeX pages, 4 figure

Produção de lipase a partir de leveduras não convencionais isoladas do bagaço de caju

As lipases (E.C. 3.1.1.3) são uma classe de enzimas que catalisam a hidrólise dos triglicerídeos de ácidos gordos livres e glicerol. Essas enzimas encontram uma grande aplicação nas indústrias de alimentos, detergentes, cosméticos, síntese orgânica e farmacêutica. Neste trabalho, as leveduras Candida tropicalis e Meyerozyma caribbica isoladas do bagaço de caju foram testadas quanto à sua capacidade de produção de lipase. As fermentações foram conduzidas em agitador rotatório a 30 °C e 170 rpm. A medida da atividade foi feita através da hidrólise com o pNFL (p-nitrofenil laurato). Para a produção da enzima foi utilizado um meio de cultura contendo resíduos agroindustriais, nomeadamente melaço 10 g/L, milhocina 4 g/L, águas russas 1,0 % (v/v). A atividade do sobrenadante da C. tropicalis foi 233 ± 10 U/L e da M. caribbica foi 146 ± 7,30 U/L em 24 h de fermentação. Esses resultados mostram o potencial dessas estirpes para a produção da enzima lipase a partir de resíduos agroalimentares

Produção de lipase a partir de Candida rugosa NRRL Y-95 utilizando meio de cultura contendo resíduos agroindustriais

As lipases (E.C. 3.1.1.3) são um grupo de enzimas capazes de catalisar a hidrólise da ligação éster de triacilgliceróis, gerando ácidos graxos livres e glicerol. As lipases microbianas são muito utilizadas nas aplicações industriais nas áreas de alimentos, síntese orgânica e farmacêutica. Neste trabalho, visando à produção de lipase a partir da levedura Candida rugosa foram utilizados meios de cultura alternativos compostos por melaço, milhocina e águas russas. As fermentações foram conduzidas em agitador rotatório a 30 °C e 170 rpm. Testaram-se quatro meios contendo diferentes combinações dos resíduos acima mencionados. O meio contendo melaço 10 g/L, milhocina 4 g/L e águas russas 1,0 %(v/v) foi o que propiciou a produção de enzima com maior atividade intracelular 269 ± 10 U/L frente ao substrato pNFL (p-nitrofenil laurato). Esses resultados demonstram que o referido meio alternativo contendo resíduos agroindustriais é adequado para a produção de lipase

MATHEMATICAL MODELING AND SIMULATION OF CO2 REMOVAL FROM AN ALKALINE SOLUTION FOR FUEL CELLS APPLICATIONS

In order to reduce oil dependency and reduce CO2 emissions stabilizing the greenhouse effect on the planet, the search for new renewable energy sources has been intensified, with a particular interest in hydrogen based solutions. Hydrogen can be used in fuel cells, which have several applications. Fuel Cells are among the environmentally friendly energy conversion systems for the 21st century with simple components such as membrane, catalyst, rearrangeable configurations that allow them to accommodate space limitations, and their use of hydrogen and oxygen. There are many types of fuel cells that are distinguished by the electrolyte type and their operating temperature. Alkaline Membrane Fuel Cells (AMFCs) and Proton-Exchange Membrane Fuel Cells (PEMFCs) are major types that work in low temperatures and produce only H2O and electricity as part of the electrochemical reaction. AMFC is a fuel cell that has more affordable membranes, when compared to the PEMFC that uses a polymeric membrane with high cost, making applications more expensive. In AMFCs, the alkaline membrane used, is a simple filter paper saturated with KOH solution that allows ions to pass through the membrane, however, suffers CO2 poisoning when it gets in contact to the carbon dioxide present in the air, reacting in the KOH and capturing hydroxyl ions. The poisoning will generate chemical compounds that will interfere with the energy generation and efficiency of the fuel cell. The main cause of the decreasing performance of carbonate formation is the precipitation of large metal carbonate crystals such as K2CO3 and the formation of H2O in the membrane, decreasing KOH concentration. If not addressed, this issue will limit the use of AMFC to pure oxygen applications only, instead of the air itself, which restricts the applicability of the technology. This study presents a mathematical model of a purifier that reduces the concentration of CO2 present in the air, improving conditions to be used in AMFC for mobile applications as automotive vehicles and without the need to use pure oxygen

Metazoários parasitos de Hoplias malabaricus (Erythrinidae) da Bacia Igarapé Fortaleza, Estado do Amapá, Norte do Brasil.

PAR110

Endohelmintos de Metynnis hypsauchen da Bacia do Rio Jari, Estado do Amapá, Brasil.

PAR057

Helmintos endoparasitos de Mylossoma duriventris da Bacia do Rio Jari, Estado do Amapá, Brasil.

PAR058