The December 2015 re-brightening of V404 Cyg: Variable absorption from the accretion disc outflow

In December 2015 the black hole binary V404 Cyg underwent a secondary outburst after the main June 2015 event. We monitored this re-brightening with the INTEGRAL and Swift satellites, and in this paper we report the results of the time-resolved spectral analysis of these data. The December outburst shared similar characteristics with the June one. The well sampled INTEGRAL light curve shows up to 10 Crab flares, which are separated by relatively weak non-flaring emission phases when compared to the June outburst. The spectra are well described by absorbed Comptonization models, with hard photon indices, $\Gamma \lesssim 2$, and significant detections of a high-energy cut-off only during the bright flares. This is in contrast to the June outburst, where the Comptonization models gave electron temperatures mostly in the 30--50 keV range, while some spectra were soft ($\Gamma \sim 2.5$) without signs of any spectral cut-off. Similarly to the June outburst, we see clear sings of a variable local absorber in the soft energy band covered by Swift/XRT and INTEGRAL/JEM-X, which causes rapid spectral variations observed during the flares. During one flare, both Swift and INTEGRAL captured V404 Cyg in a state where the absorber was nearly Compton thick, $N_\textrm{H} \approx 10^{24}\,\textrm{cm}^{-2}$, and the broad band spectrum was similar to obscured AGN spectra, as seen during the "plateaus" in the June outburst. We conclude that the spectral behaviour of V404 Cyg during the December outburst was analogous with the first few days of the June outburst, both having hard X-ray flares that were intermittently influenced by obscuration due to nearly Compton-thick outflows launched from the accretion disc.Comment: 9 pages, 6 figures, accepted to A&

Cellulolytic ability of Penicillium strains isolated from soil of the Brazilian Atlantic forest

Penicillium spp. are capable of degrading plant wastes by producing large amounts of enzymes such as cellulases. These form a complex capable of acting on cellulosic materials and producing sugars with industrial interest (e.g., ethanol production). Cellulases are also used for (a) pulp and paper industry (b) in the textile industry. The aim of this study was to evaluate the cellulolytic capability of 17 strains of Penicillium isolated from soil of the Brazilian Atlantic Forest and conserved under mineral oil at the URM Culture Collection. All strains were re-grown from mineral oil and re-identifiied. Each strain was grown in synthetic medium with carboxymethylcellulose as the carbon source and incubated for 5 days at 28°C. Strains were subjected to heat shock for 16h at 50°C. Thereafter, onto each colony was added 5 ml of Congo red stain solution in Tris-HCl. After 30 min this solution was removed and the cultures were washed and submerged under 0.1 M NaCl aqueous solution for 5 min. Finally, an enzymatic index was calculated from the ratio of the diameter of the halo around each colony to the diameter of the colony. All of the 17 strains tested showed a halo of cellulose degradation, indicating enzyme production. The enzymatic ratios varied between 0.2 (Penicillium brevicompactum URM5994) and 3.3 (Penicillium glabrum URM6009). Thus, Penicillium glabrum URM6009 is evaluated as a high producer of cellulase. It was selected for quantitative production of this enzyme and additional studies are taking place in order to verify potential industrial application for clarification of fruit juices

Rapid spectral transition of the black hole binary V404 Cyg

During the June 2015 outburst of the black hole binary V404 Cyg, rapid changes in the X-ray brightness and spectra were common. The INTEGRAL monitoring campaign detected spectacular Eddington-limited X-ray flares, but also rapid variations at much lower flux levels. On 2015 June 21 at 20 h 50 min, the 3-10 keV JEM-X data as well as simultaneous optical data started to display a gradual brightening from one of these low-flux states. This was followed 15 min later by an order-of-magnitude increase of flux in the 20-40 keV IBIS/ISGRI light curve in just 15 s. The best-fitting model for both the pre- and post-transition spectra required a Compton-thick partially covering absorber. The absorber parameters remained constant, but the spectral slope varied significantly during the event, with the photon index decreasing from $\Gamma \approx 3.7$ to $\Gamma \approx 2.3$. We propose that the rapid 20-40 keV flux increase was either caused by a spectral state transition that was hidden from our direct view, or that there was a sudden reduction in the amount of Compton down-scattering of the primary X-ray emission in the disk outflow.Comment: 6 pages, 2 figures, accepted to A&

Detection of Very Low-Frequency Quasi-Periodic Oscillations in the 2015 Outburst of V404 Cygni

In June 2015, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift/XRT, Fermi/GBM, Chandra/ACIS, INTEGRAL's IBIS/ISGRI and JEM-X, and NuSTAR. We report the detection of a QPO at 18 mHz simultaneously with both Fermi/GBM and Swift/XRT, another example of a rare but slowly growing new class of mHz-QPOs in BHXRBs linked to sources with a high orbital inclination. Additionally, we find a duo of QPOs in a Chandra/ACIS observation at 73 mHz and 1.03 Hz, as well as a QPO at 136 mHz in a single Swift/XRT observation that can be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is significant structure in the broadband power, with a strong feature observable in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the context of current models for QPO formation.Comment: 17 pages, 9 figures, published in Ap

Late-onset neonatal sepsis in preterm infants with birth weight under 1.500g

Objective: the research objective was to characterize preterm infants with birth weight under 1500 g, and to identify the incidence of late-onset neonatal sepsis among this population. Methods: a prospective cohort study with a sample of 30 preterm newborns that weighed under 1500 g and were hospitalized in the NICU of the university hospital. Data were collected from January to December 2013 using a structured instrument. Results: of the 30 neonates included in the study, 14 developed late-onset neonatal sepsis with a prevalence of coagulase-negative staphylococci. Conclusions: the incidence of late-onset neonatal sepsis indicates a vulnerability in preterm infants due to immunological immaturity. These results reveal that knowledge of the profi le of newborn infants admitted to the NICU and the risk factors to which they are exposed are central to the planning of nursing care for these patients. Future studies should address strategies for preventing nosocomial infection

The optical counterpart of the bright X-ray transient Swift J1745-26

We present a 30-day monitoring campaign of the optical counterpart of the bright X-ray transient Swift J1745-26, starting only 19 minutes after the discovery of the source. We observe the system peaking at i' ~17.6 on day 6 (MJD 56192) to then decay at a rate of ~0.04 mag/day. We show that the optical peak occurs at least 3 days later than the hard X-ray (15-50 keV) flux peak. Our measurements result in an outburst amplitude greater than 4.3 magnitudes, which favours an orbital period < 21 h and a companion star with a spectral type later than ~ A0. Spectroscopic observations taken with the GTC-10.4 m telescope reveal a broad (FWHM ~ 1100 km/s), double-peaked H_alpha emission line from which we constrain the radial velocity semi-amplitude of the donor to be K_2 > 250 km/s. The breadth of the line and the observed optical and X-ray fluxes suggest that Swift J1745-26 is a new black hole candidate located closer than ~7 kpc.Comment: 5 pages, 4 figures, accepted for publication in MNRA

Avaliação de cultivares de milho no Território Federal de Rondônia.

Procurou-se identificar melhores cultivares de milho para uso imediato dos agricultores. Os experimentos foram instalados em Ouro Preto, RO, no periodo de 1977/78, com dois ensaios, sendo um de milho normal e outro braquitico. O solo foi do tipo Podzolico Vermelho Amarelo distrofico. Foi feita adubacao mineral de NPK, 60-60-60. Resultados demonstram que as melhores cultivares de milho normal foram: Composto Dentado, Centralmex, Poza Rica e Yousafwala 7428 e Composto A; Milho braquitico: Composto Dentado Brachitico, Piranao e Composto Dentado Braquitico x Composto Flint Braquitico.bitstream/item/46846/1/COT-8-19790001.pd

Enhancement of Friction between Carbon Nanotubes: An Efficient Strategy to Strengthen Fibers

Interfacial friction plays a crucial role in the mechanical properties of carbon nanotube based fibers, composites, and devices. Here we use molecular dynamics simulation to investigate the pressure effect on the friction within carbon nanotube bundles. It reveals that the intertube frictional force can be increased by a factor of 1.5 ~ 4, depending on tube chirality and radius, when all tubes collapse above a critical pressure and when the bundle remains collapsed with unloading down to atmospheric pressure. Furthermore, the overall cross-sectional area also decreases significantly for the collapsed structure, making the bundle stronger. Our study suggests a new and efficient way to reinforce nanotube fibers, possibly stronger than carbon fibers, for usage at ambient conditions.Comment: revtex, 5 pages, accepted by ACS Nano 10 Dec 200