Evolution of the bursting-layer wave during a Type 1 X-ray burst

In a popular scenario due to Heyl, quasi periodic oscillations (QPOs) which are seen during type 1 X-ray bursts are produced by giant travelling waves in neutron-star oceans. Piro and Bildsten have proposed that during the burst cooling the wave in the bursting layer may convert into a deep crustal interface wave, which would cut off the visible QPOs. This cut-off would help explain the magnitude of the QPO frequency drift, which is otherwise overpredicted by a factor of several in Heyl's scenario. In this paper, we study the coupling between the bursting layer and the deep ocean. The coupling turns out to be weak and only a small fraction of the surface-wave energy gets transferred to that of the crustal-interface wave during the burst. Thus the crustal-interface wave plays no dynamical role during the burst, and no early QPO cut-off should occur.Comment: 8 pages, submitted to MNRA

Discovery of coherent millisecond X-ray pulsations in Aql X-1

We report the discovery of an episode of coherent millisecond X-ray pulsation in the neutron star low-mass X-ray binary Aql X-1. The episode lasts for slightly more than 150 seconds, during which the pulse frequency is consistent with being constant. No X-ray burst or other evidence of thermonuclear burning activity is seen in correspondence with the pulsation, which can thus be identified as occurring in the persistent emission. The pulsation frequency is 550.27 Hz, very close (0.5 Hz higher) to the maximum reported frequency from burst oscillations in this source. Hence we identify this frequency with the neutron star spin frequency. The pulsed fraction is strongly energy dependent, ranging from 10% (16-30 keV). We discuss possible physical interpretations and their consequences for our understanding of the lack of pulsation in most neutron star low-mass X-ray binaries. If interpreted as accretion-powered pulsation, Aql X-1 might play a key role in understanding the differences between pulsating and non-pulsating sources.Comment: 5 pages, 3 figures, accepted by ApJ Letters after minor revisions. Slightly extended discussion. One author added. Uses emulateapj.cl

Necrotizing Fasciitis Post- Acute Appendicitis

A Fasceíte Necrotizante (FN) é um processo infeccioso da fascia profunda, de evolução rápida e progressiva com necrose secundária do tecido celular subcutâneo. Os autores apresentam um caso de FN da parede abdominal, como complicação extremamente rara de apendicite aguda. Trata-se de uma criança, apendicectomizada por apendicite aguda gangrenada, que evolui para quadro infeccioso grave, com dor e processo inflamatório da parede abdominal. Após diagnóstico, foi submetido a desbridamento cirúrgico da parede abdominal e drenagem de abcesso intraperitoneal. Realizada terapêutica antibiótica, desbridamentos cirúrgicos e pensos sucessivos da lesão e ao 22º dia efectuou-se enxerto dermo-epidérmico de área cruenta residual da parede abdominal. Porque o prognóstico está intimamente relacionado com o tempo decorrido até ao diagnóstico correcto e início de terapêutica adequada, é de extrema importância que este diagnóstico seja considerado

A complex state transition from the black hole candidate Swift J1753.5-0127

We present our monitoring campaign of the outburst of the black-hole candidate Swift J1753.5-0127, observed with the Rossi X-ray Timing Explorer and the Swift satellites. After ~4.5 years since its discovery, the source had a transition to the hard intermediate state. We performed spectral and timing studies of the transition showing that, unlike the majority of the transient black holes, the system did not go to the soft states but it returned to the hard state after a few months. During this transition Swift J1753.5-0127 features properties which are similar to those displayed by the black hole Cygnus X-1. We compared Swift J1753.5-0127 to one dynamically confirmed black hole and two neutron stars showing that its power spectra are in agreement with the binary hosting a black hole. We also suggest that the prolonged period at low flux that followed the initial flare is reminiscent of that observed in other X-ray binaries, as well as in cataclysmic variables.Comment: Accepted for publication in MNRA

Spectral evidence for jets from Accreting Millisecond X-ray Pulsars

Transient radio emission from X-ray binaries is associated with synchrotron emission from collimated jets that escape the system, and accreting millisecond X-ray pulsars (AMXPs) are no exception. Although jets from black hole X-ray binaries are well-studied, those from neutron star systems appear much fainter, for reasons yet uncertain. Jets are usually undetectable at higher frequencies because of the relative brightness of other components such as the accretion disc. AMXPs generally have small orbital separations compared with other X-ray binaries and as such their discs are relatively faint. Here, I present data that imply jets in fact dominate the radio-to-optical spectrum of outbursting AMXPs. They therefore may provide the best opportunity to study the behaviour of jets produced by accreting neutron stars, and compare them to those produced by black hole systems.Comment: 4 pages, 2 figures, to appear in the proceedings of "A Decade of Accreting Millisecond X-ray Pulsars", Amsterdam, April 2008, eds. R. Wijnands et al. (AIP Conf. Proc.

Reaction kinetics of muonium with the halogen gases (F2, Cl2, and Br2)

Copyright @ 1989 American Institute of PhysicsBimolecular rate constants for the thermal chemical reactions of muonium (Mu) with the halogen gases—Mu+X2→MuX+X—are reported over the temperature ranges from 500 down to 100, 160, and 200 K for X2=F2,Cl2, and Br2, respectively. The Arrhenius plots for both the chlorine and fluorine reactions show positive activation energies Ea over the whole temperature ranges studied, but which decrease to near zero at low temperature, indicative of the dominant role played by quantum tunneling of the ultralight muonium atom. In the case of Mu+F2, the bimolecular rate constant k(T) is essentially independent of temperature below 150 K, likely the first observation of Wigner threshold tunneling in gas phase (H atom) kinetics. A similar trend is seen in the Mu+Cl2 reaction. The Br2 data exhibit an apparent negative activation energy [Ea=(−0.095±0.020) kcal mol−1], constant over the temperature range of ∼200–400 K, but which decreases at higher temperatures, indicative of a highly attractive potential energy surface. This result is consistent with the energy dependence in the reactive cross section found some years ago in the atomic beam data of Hepburn et al. [J. Chem. Phys. 69, 4311 (1978)]. In comparing the present Mu data with the corresponding H atom kinetic data, it is found that Mu invariably reacts considerably faster than H at all temperatures, but particularly so at low temperatures in the cases of F2 and Cl2. The current transition state calculations of Steckler, Garrett, and Truhlar [Hyperfine Interact. 32, 779 (986)] for Mu+X2 account reasonably well for the rate constants for F2 and Cl2 near room temperature, but their calculated value for Mu+Br2 is much too high. Moreover, these calculations seemingly fail to account for the trend in the Mu+F2 and Mu+Cl2 data toward pronounced quantum tunneling at low temperatures. It is noted that the Mu kinetics provide a crucial test of the accuracy of transition state treatments of tunneling on these early barrier HX2 potential energy surfaces.NSERC (Canada), Donors of the Petroleum Research Fund, administered by the American Chemical Society, for their partial support of this research and the Canada Council

Parsec-Scale Bipolar X-ray Shocks Produced by Powerful Jets from the Neutron Star Circinus X-1

We report the discovery of multi-scale X-ray jets from the accreting neutron star X-ray binary, Circinus X-1. The bipolar outflows show wide opening angles and are spatially coincident with the radio jets seen in new high-resolution radio images of the region. The morphology of the emission regions suggests that the jets from Circinus X-1 are running into a terminal shock with the interstellar medium, as is seen in powerful radio galaxies. This and other observations indicate that the jets have a wide opening angle, suggesting that the jets are either not very well collimated or precessing. We interpret the spectra from the shocks as cooled synchrotron emission and derive a cooling age of approximately 1600 yr. This allows us to constrain the jet power to be between 3e35 erg/s and 2e37 erg/s, making this one of a few microquasars with a direct measurement of its jet power and the only known microquasar that exhibits stationary large-scale X-ray emission.Comment: 5 pages, 4 figures, to be published in the Astrophysical Journal Letter

Controlateral Symmetrisation in SRM for Breast Cancer: Now or Then? Immediate versus Delayed Symmetrisation in a Two-Stage Breast Reconstruction

Introduction: The timing of contralateral symmetrisation in patients with large and ptotic breasts undergoing a unilateral skin-reducing mastectomy (SRM) is one of the most debated topics in the reconstructive field. There is no evidence to support the advantage of immediate or delayed symmetrisation to help surgeons with this decision. The aim of this study was to investigate the clinical and aesthetic outcomes of immediate symmetrisation. Methods: A randomised observational study was conducted on patients who underwent an SRM for unilateral breast cancer. Based on a simple randomisation list, patients were divided into two groups: a delayed symmetrisation group versus an immediate symmetrisation group. The postoperative complications, BREAST-Q outcomes and reoperations were compared. Results: Out of a total of 84 patients undergoing an SRM between January 2018 and January 2021, 42 patients underwent immediate symmetrisation and 42 patients had delayed symmetrisation. Three implant losses (7.2%) were observed and we reported three wound dehiscences; one of these was in a contralateral breast reconstruction in the immediate symmetrisation group. The BREAST-Q patient-reported outcome measures recorded better aesthetic outcomes and a high patient satisfaction for the immediate symmetrisation group. Conclusions: Simultaneous controlateral symmetrisation is a good alternative to achieve better satisfaction and quality of life for patients; from a surgical point of view, it does not excessively impact on the second time of reconstruction