Sub-second periodicity in a fast radio burst.

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light years1. The nature of their progenitors and their emission mechanism remain open astrophysical questions2. Here we report the detection of the multicomponent FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5σ. The long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere3,4, as opposed to emission regions located further away from the star, as predicted by some models5.

Comparison of different chemical treatments of brush and flat carbon electrodes to improve performance of microbial fuel cells.

Anodes in microbial fuel cells (MFCs) can be chemically treated to improve performance but the impact of treatment on power generation has not been examined for different electrode base materials. Brush or flat anodes were chemically treated and then compared in identical two-chambered MFCs using the electrode potential slope (EPS) analysis to quantify the anode resistances. Flat carbon cloth anodes modified with carbon nanotubes (CNTs) produced 1.42 ± 0.06 W m-2, which was 3.2 times more power than the base material (0.44 ± 0.00 W m-2), but less than the 2.35 ± 0.1 W m-2 produced using plain graphite fiber brush anodes. An EPS analysis showed that there was a 90% decrease in the anode resistances of the CNT-treated carbon cloth and a 5% decrease of WO3 nanoparticle-treated brushes compared to unmodified controls. Certain chemical treatments can therefore improve performance of flat anodes, but plain brush anodes achieved the highest power densities.

Searching for Gravitational Waves from Cosmological Phase Transitions with the NANOGrav 12.5-Year Dataset.

We search for a first-order phase transition gravitational wave signal in 45 pulsars from the NANOGrav 12.5-year dataset. We find that the data can be modeled in terms of a strong first order phase transition taking place at temperatures below the electroweak scale. However, we do not observe any strong preference for a phase-transition interpretation of the signal over the standard astrophysical interpretation in terms of supermassive black hole mergers; but we expect to gain additional discriminating power with future datasets, improving the signal to noise ratio and extending the sensitivity window to lower frequencies. An interesting open question is how well gravitational wave observatories could separate such signals.

Relaçäo entre frequência das mamadas a dor, fissuras dos mamilos e volume de secreçäo láctea / Relation between suckling frequency, pain, nipple fissures and volume of milks secretion

Apresenta-se uma investigaçäo, à fim de determinar os efeitos da freqüência das mamas na incidência da dor, na ocorrência de fissura do mamilo e na produçäo de leite pela nutriz. Foram estudadas 30 mäes durante os primeiros 15 dias após o parto. As mäes foram orientadas segundo a rotina da maternidade do hospital escola a adotarem um horário livre de mamadas ao peito para os seus recém-nascidos. Durante os primeiros 14 dias após o parto todas as mäes anotaram em folhas especiais a freqüência das mamadas diàriamente, assim como o aparecimento e intensidade da dor dos mamilos e a ocorrência de fissura no mesmo. O volume de leite foi avaliado de forma subjetiva pela mäe, também em regime de observaçäo diária (24 h). Os resultados desta investigaçäo demonstraram que o aumento na freqüência das mamadas, numa fase inicial da amamentaçäo ao peito: 1) näo acarreta necessariamente um aumento da dor nos mamilos e na ocorrência de fissura dos mesmos, 2) leva a um significativo aumento da quantidade de leite segundo relato da nutriz