The origin of RXJ1856.5-3754 and RXJ0720.4-3125 -- updated using new parallax measurements

RXJ1856 and RXJ0720 are the only young isolated radio-quiet neutron stars (NSs) for which trigonometric parallaxes were measured. Due to detection of their thermal emission in X-rays they are important to study NS cooling and to probe theoretical cooling models. Hence, a precise determination of their age is essential. Recently, new parallax measurements of RXJ1856 and RXJ0720 were obtained. Considering that NSs may originate from binary systems that got disrupted due to an asymmetric supernova, we attempt to identify runaway stars which may have been former companions to the NS progenitors. Such an identification would strongly support a particular birth scenario with time and place. We trace back each NS, runaway star and the centres of possible birth associations to find close encounters. The kinematic age is then given by the time since the encounter. We use Monte Carlo simulations to account for observational uncertainties. Using the most recent parallax measurement of 8.16+/-0.80 mas for RXJ1856, we find that it originated in the U Sco association 0.46+/-0.05 Myr ago. This is slightly larger than the value we reported earlier (0.3 Myr). Our result is strongly supported by its current radial velocity that we predict to be 6+19-20 km/s. This implies an inclination angle of 88+/-6 deg consistent with the bow shock. No suitable runaway star was found to be a potential former companion of RXJ1856. Making use of a recent parallax measurement for RXJ0720 of 3.6+/-1.6 mas, we find that this NS was possibly born in Tr 10 0.85+/-0.15 Myr ago. This is somewhat larger than the one obtained using the old parallax value (0.5 Myr). We suggest the B0 runaway supergiant HIP 43158 as a candidate for a former companion. Then, the current distance of RXJ0720 to the Sun should be 286+27-23 pc, in agreement with recent measurements. We then expect the radial velocity of RXJ0720 to be -76+34-17 km/s.Comment: accepted for publication in MNRAS additional supporting material can be found at http://www.astro.uni-jena.de/~nina/supporting_info.pdf the abstract has been adjusted to fit the length requirement (RXJ1856 = RXJ1856.5-3754, RXJ0720 = RXJ0720.4-3125, U Sco = Upper Scorpius, Tr 10 = Trumpler 10

New resampling method for evaluating stability of clusters

<p>Abstract</p> <p>Background</p> <p>Hierarchical clustering is a widely applied tool in the analysis of microarray gene expression data. The assessment of cluster stability is a major challenge in clustering procedures. Statistical methods are required to distinguish between real and random clusters. Several methods for assessing cluster stability have been published, including resampling methods such as the bootstrap.</p> <p>We propose a new resampling method based on continuous weights to assess the stability of clusters in hierarchical clustering. While in bootstrapping approximately one third of the original items is lost, continuous weights avoid zero elements and instead allow non integer diagonal elements, which leads to retention of the full dimensionality of space, i.e. each variable of the original data set is represented in the resampling sample.</p> <p>Results</p> <p>Comparison of continuous weights and bootstrapping using real datasets and simulation studies reveals the advantage of continuous weights especially when the dataset has only few observations, few differentially expressed genes and the fold change of differentially expressed genes is low.</p> <p>Conclusion</p> <p>We recommend the use of continuous weights in small as well as in large datasets, because according to our results they produce at least the same results as conventional bootstrapping and in some cases they surpass it.</p

Statistical tests for the comparison of two samples:the general alternative

It is common to test the null hypothesis that two samples were drawn from identical distributions; and the Smirnov (sometimes called Kolmogorov-Smirnov) test is conventionally applied. We present simulation results to compare the performance of this test with three recently introduced alternatives. We consider both continuous and discrete data. We show that the alternative methods preserve type I error at the nominal level as well as the Smirnov test but offer superior power. We argue for the routine replacement of the Smirnov test with the modified Baumgartner test according to Murakami (2006), or with the test proposed by Zhang (2006).</p

Early Clinical Outcomes of Surgical Myocardial Revascularization for Acute Coronary Syndromes Complicated by Cardiogenic Shock: A Report From the North-Rhine-Westphalia Surgical Myocardial Infarction Registry

Background-Coronary artery bypass grafting for acute coronary syndrome complicated by cardiogenic shock (CS) is associated with a high mortality. This registry study aimed to distinguish between early surgical outcomes of CS patients with non-ST-segment-elevation myocardial infarction (NSTEMI) and ST-segment-elevation myocardial infarction (STEMI). Methods and Results-Patients with NSTEMI (n=1218) or STEMI (n=618) referred for coronary artery bypass grafting were enrolled in a prospective multicenter registry between 2010 and 2017. CS was present in 227 NSTEMI (18.6%) and 243 STEMI patients (39.3%). Key clinical end points were in-hospital mortality (IHM) and major adverse cardiocerebral events (MACCEs). Predictors for IHM and MACCEs were identified using multivariable logistic regression analysis. STEMI patients with CS were younger, had a lower prevalence of diabetes mellitus and multivessel disease, and exhibited higher myocardial injury (troponin 9 +/- 17 versus 3 +/- 6 ng/mL) before surgery compared with patients with NSTEMI (P<0.05). Emergency coronary artery bypass grafting was performed more often in STEMI (58%) versus NSTEMI (40%; P=0.002). On-pump surgery with cardioplegia was the preferred surgical technique in CS. IHM and MACCE rates were 24% and 49% in STEMI patients with CS and were higher compared with NSTEMI (IHM 15% versus MACCE 34%; P<0.001). Predictors for IHM and MACCE in CS were a reduced ejection fraction and a higher European System for Cardiac Operative Risk Evaluation score. Conclusions-Surgical revascularization in NSTEMI and STEMI patients with CS is associated with a substantial but not prohibitive IHM and MACCE rate. Worse early outcomes were found for patients with STEMI complicated by CS compared with NSTEMI patients

Coronary Artery Bypass Graft Surgery in Patients With Acute Coronary Syndromes After Primary Percutaneous Coronary Intervention: A Current Report From the North-Rhine Westphalia Surgical Myocardial Infarction Registry

Background Coronary artery bypass grafting has remained an important treatment option for acute coronary syndromes, particularly in patients (1) with ongoing ischemia and large areas of jeopardized myocardium, if percutaneous coronary intervention (PCI) cannot be performed; (2) following successful PCI of the culprit lesion with further indication for coronary artery bypass grafting; and (3) where PCI is incomplete, not sufficient, or failed. Methods and Results We aimed to analyze coronary artery bypass grafting outcome following prior PCI in acute coronary syndromes from the North-Rhine-Westphalia surgical myocardial infarction registry comprising 2616 patients. Primary end points were in-hospital all-cause mortality and major adverse cardio-cerebral event. Patients were 68 +/- 11 years of age, had 3-vessel and left main-stem disease in 80.4% and 45.3%, presenting a logistic EuroSCORE of 15.1% in unstable angina, 20.3% in non-ST-segment-elevation myocardial infarction, and 23.5% in ST-segment-elevation myocardial infarction. A history of PCI was present in 36.2% and PCI was performed within 24 hours before surgery in 5.2% in unstable angina, 5.9% in non-ST-segment-elevation myocardial infarction, and 16.1% in ST-segment-elevation myocardial infarction. PCI failed in 5.3% in unstable angina, 6.8% in non-ST-segment-elevation myocardial infarction and 17.2% in ST-segment-elevation myocardial infarction, and 28.8% of patients presented with cardiogenic shock. In-hospital mortality without PCI was 7.4%, but increased to 8.7% with prior PCI >24 hours, 14.5% with prior PCI 24 hours, 25.6% with prior PCI <24 hours, and 41.3% with failed PCI (P=0.014). Multivariable logistic regression analysis showed prior PCI (P=0.039), as well as failed PCI (P=0.001) to be predictors for in-hospital all-cause mortality and major adverse cardio-cerebral event. Conclusions In the current PCI era, immediately prior or failed PCI before coronary artery bypass grafting in acute coronary syndromes is associated with high perioperative risk, cardiogenic shock, and increased morbidity and mortality