It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion ...stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Purpose
MMP9 is a matricellular protein associated with extracellular matrix (ECM) remodelling, that promotes tumour progression, and modulates the activity of cell adhesion molecules and cytokines. ...This study aims to assess the prognostic value of MMP9 and its association with cytoskeletal modulators in early-stage invasive breast cancer (BC).
Methods
MMP9 expression was evaluated by immunohistochemistry using a well-characterised series of primary BC patients with long-term clinical follow-up. Association with clinicopathological factors, patient outcome and ECM remodelling BC-biomarkers were investigated. METABRIC dataset, BC-GenExMiner v4.0 and TCGA were used for the external validation of
MMP9
expression. GSEA gene enrichment analyses were used to evaluate
MMP9
associated pathways.
Results
MMP9 immunopositivity was observed in the stroma and cytoplasm of BC cells. Elevated MMP9 protein levels were associated with high tumour grade, high Nottingham Prognostic Index, and hormonal receptor negativity. Elevated MMP9 protein expression correlated significantly with cytokeratin 17 (Ck17), Epidermal Growth Factor Receptor (EGFR), proliferation (Ki67) biomarkers, cell surface adhesion receptor (CD44) and cell division control protein 42 (CDC42). Cytoplasmic MMP9 expression was an independent prognostic factor associated with shorter BC-specific survival. In the external validation cohorts,
MMP9
expression was also associated with poor patients’ outcome. Transcriptomic analysis confirmed a positive association between
MMP9
and ECM remodelling biomarkers. GSEA analysis supports MMP9 association with ECM and cytoskeletal pathways.
Conclusion
This study provides evidence for the prognostic value of MMP9 in BC. Further functional studies to decipher the role of MMP9 and its association with cytoskeletal modulators in BC progression are warranted.
The source IGR J18245–2452 is the fifteenth discovered accreting millisecond X-ray pulsar and the first neutron star to show direct evidence of a transition between accretion- and rotation-powered ...emission states. These swings provided the strongest confirmation to date of the pulsar recycling scenario. During the two XMM-Newton observations that were carried out while the source was in outburst in April 2013, IGR J18245–2452 displayed a unique and peculiar X-ray variability. In this work, we report on a detailed analysis of the XMM-Newton data and focus on the timing and spectral variability of the source. In the 0.4–11 keV energy band, IGR J18245–2452 continuously switched between lower and higher intensity states, with typical variations in flux by factor of ~100 on time scales as short as a few seconds. These variations in the source intensity were sometimes accompanied by dramatic spectral hardening, during which the X-ray power-law photon index varied from Γ = 1.7 to Γ = 0.9. The pulse profiles extracted at different count-rates, hardnesses, and energies also showed a complex variability. These phenomena were never observed in accreting millisecond X-ray pulsars, at least not on such a short time-scale. Fast variability was also found in the 5.5 and 9 GHz ATCA radio observations that were carried out for about 6 h during the outburst. We interpret the variability observed from IGR J18245–2452 in terms of a hiccup accretion phase, during which the accretion of material from the inner boundary of the Keplerian disk is reduced by the onset of centrifugal inhibition of accretion, possibly causing the launch of outflows. Changes across accretion and propeller regimes have been long predicted and reproduced by magnetohydrodynamic simulations of accreting millisecond X-ray pulsars, but have never observed to produce as extreme a variability as that shown by IGR J18245–2452.
Context. Jets from rotation-powered pulsars so far have only been observed in systems moving subsonically through their ambient medium and/or embedded in their progenitor supernova remnant (SNR). ...Supersonic runaway pulsars are also expected to produce jets, but they have not been confirmed to so far. Aims. We investigated the nature of the jet-like structure associated with the INTEGRAL source IGR J11014-6103 (the “Lighthouse nebula”). The source is a neutron star escaping its parent SNR MSH 11-61A supersonically at a velocity exceeding 1000 km s-1. Methods. We observed the Lighthouse nebula and its jet-like X-ray structure through dedicated high spatial resolution observations in X-rays (with Chandra) and in the radio band (with ATCA). Results. Our results show that the feature is a true pulsar’s jet. It extends highly collimated over ≳11pc, displays a clear precession-like modulation, and propagates nearly perpendicular to the system direction of motion, implying that the neutron star’s spin axis in IGR J11014-6103 is almost perpendicular to the direction of the kick received during the supernova explosion. Conclusions. Our findings suggest that jets are common to rotation-powered pulsars, and demonstrate that supernovae can impart high kick velocities to misaligned spinning neutron stars, possibly through distinct, exotic, core-collapse mechanisms.
IGR J11014-6103 (also known as the Lighthouse Nebula) is composed of a bow-shock pulsar wind nebula (PWN) and large-scale X-ray jet-like features, all powered by PSR J1101-6101. Previous observations ...suggest that the jet features stem from a ballistic jet of relativistic particles. In order to confirm the nature of the jet and the counter-jet, we obtained a new deep 250 ks Chandra observation of the Lighthouse Nebula. We performed detailed spatial and spectral analysis of all X-ray components of the system. The X-ray PWN is now better resolved and shows a peculiar morphology resembling the shape of an arrow. The overall helical pattern of the main jet is confirmed. However, there are large deviations from a simple helical model at small and large scales. Significant extended emission is now detected, encompassing the main jet all along its length. The presence of an apparent gap along the main jet at ~50″ distance from the pulsar is confirmed; however, the surrounding extended emission prevents conclusions on the coherence at this position of the jet. The counter-jet is now detected at high statistical significance. In addition, we found two small-scale arcs departing from the pulsar towards the jets. We also looked for possible bow-shock emission due to the pulsar motion, with a short VLT/FORS2 H-α observation. No clear emission is found, most likely because of the contamination from a diffuse nebulosity. The results of our X-ray analysis show that both a ballistic jet scenario and an alternative scenario involving the diffusion of particles along pre-existing interstellar magnetic field lines are able to satisfactorily explain some of the observational evidence, but cannot fully reproduce the observations.
Objective
To evaluate feasibility and validate both safety and efficiency of radiological percutaneous periprosthetic bone cementoplasty (RPPBC) performed under local anesthesia as an alternative ...minimally invasive treatment of aseptic implant loosening.
Methods
In this case series, seven patients (mean age 81 years, range 73 to 89 years, 2 men and 5 women) were enrolled between February 2011 and January 2020 with confirmed aseptic loosening of orthopedic implants. One patient presented with tibial component loosening of an unicompartmental knee arthroplasty, one with glenoid component loosening from a reverse shoulder arthroplasty, one femoral gamma nail, and four presented with pedicle screw loosening after staged posterior lumbar interbody fusion. All patients underwent clinical, biochemical, and imaging assessments to confirm the diagnosis of aseptic loosening. All benefited from RPPBC under dual CT and fluoroscopic guidance. All procedures were performed under local anesthesia by an experienced radiologist. Preprocedural, immediate and 6-month post-cementoplasty pain levels on a visual analogue scale (VAS), and functional outcomes were evaluated. Immediate and 6-month postprocedural CTs were performed to evaluate the treated region.
Results
All RPPBC were well tolerated by patients throughout the procedure. None of the patients suffered from local or systemic infection post-RPPBC, or periprosthetic fractures. No recurrent implant loosening was observed. Six patients were pain free at 6 months. All patients expressed functional improvements during validated outcome score evaluations.
Conclusion
RPPBC appears to be an efficient and reliable treatment strategy for aseptic loosening of orthopedic implants in elderly patients deemed unfit for revision surgery.
Key Points
• Radiological percutaneous periprosthetic bone cementoplasty offers immediate and long-lasting pain relief in elderly frail patients, or those deemed unfit for revision surgery despite presenting with symptomatic aseptic loosening of orthopedic implants.
• Radiological percutaneous periprosthetic bone cementoplasty brings quick and long-lasting improvements in clinical functional outcomes and offer effective pain reduction, thereby improving the overall quality of life.
• Radiological percutaneous periprosthetic bone cementoplasty is a safe, quick, reliable, and well-tolerated minimally invasive procedure which can be easily performed under simple locoregional anesthesia and requires short-term hospital stay.
There is an increasing theoretical and observational evidence that the external magnetic field of magnetars may contain a toroidal component, likely of the same order of the poloidal one. Such ...‘twisted magnetospheres’ are threaded by currents flowing along the closed field lines which can efficiently interact with soft thermal photons via resonant cyclotron scatterings (RCS). Actually, RCS spectral models proved quite successful in explaining the persistent ∼1–10 keV emission from the magnetar candidates, the soft γ-ray repeaters (SGRs) and the anomalous X-ray pulsars (AXPs). Moreover, it has been proposed that, in the presence of highly relativistic electrons, the same process can give rise to the observed hard X-ray spectral tails extending up to ∼200 keV. Spectral calculations have been restricted up to now to the case of a globally twisted dipolar magnetosphere, although there are indications that the twist may be confined only to a portion of the magnetosphere, and/or that the large-scale field is more complex than a simple dipole. In this paper, we investigate multipolar, force–free magnetospheres of ultramagnetized neutron stars. We first discuss a general method to generate multipolar solutions of the Grad-Schlüter-Shafranov (GSS) equation, and analyse in detail dipolar, quadrupolar and octupolar fields. The spectra and lightcurves for these multipolar, globally twisted fields are then computed using a Monte Carlo code and compared with those of a purely dipolar configuration. Finally, the phase-resolved spectra and energy-dependent lightcurves obtained with a simple model of a locally sheared field are confronted with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the AXPs 1RXS J1708−4009 and 4U 0142+61. Results support a picture in which the field in these two sources is not globally twisted.
Melting of large Pt@MgO(1 0 0) icosahedra Rossi, K; Ellaby, T; Paz-Borbón, L O ...
Journal of physics. Condensed matter,
04/2017, Letnik:
29, Številka:
14
Journal Article
Recenzirano
Odprti dostop
On the basis of ab initio calculations, we present a new parametrisation of the Vervisch-Mottet-Goniakowski (VMG) potential (Vervisch et al 2002 Phys. Rev. B 24 245411) for modelling the oxide-metal ...interaction. Applying this model to mimic the finite temperature behaviour of large platinum icosahedra deposited on the pristine MgO(1 0 0), we find the nanoparticle undergoes two solid-solid transitions. At 650 K the 'squarisation' of the interface layer, while a full reshaping towards a fcc architecture takes place above 950 K. In between, a quite long-lived intermediate state with a (1 0 0) interface but with an icosahedral cap is observed. Our approach reproduces experimental observations, including wetting behaviour and the lack of surface diffusion.
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