Compact Binaries in Star Clusters I - Black Hole Binaries Inside Globular Clusters

We study the compact binary population in star clusters, focusing on binaries containing black holes, using a self-consistent Monte Carlo treatment of dynamics and full stellar evolution. We find that the black holes experience strong mass segregation and become centrally concentrated. In the core the black holes interact strongly with each other and black hole-black hole binaries are formed very efficiently. The strong interactions, however, also destroy or eject the black hole-black hole binaries. We find no black hole-black hole mergers within our simulations but produce many hard escapers that will merge in the galactic field within a Hubble time. We also find several highly eccentric black hole-black hole binaries that are potential LISA sources, suggesting that star clusters are interesting targets for space-based detectors. We conclude that star clusters must be taken into account when predicting compact binary population statistics.Comment: 19 pages, 5 Tables, 12 Figures, updated in response to referee report, accepted for publication in MNRA

Urinary 11-dehydro-thromboxane B_{2} as a predictor of acute myocardial infarction outcomes : results of leukotrienes and thromboxane in myocardial infarction (LTIMI) study

BACKGROUND: Urinary 11‐dehydro‐thromboxane (TX)B(2) has been described as a potential predictive biomarker of major adverse cardiovascular events (MACEs) in high cardiac risk patients. This part of LTIMI (Leukotrienes and Thromboxane In Myocardial Infarction) study aimed to evaluate the relationship between 11‐dehydro‐TXB (2) and MACEs in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: LTIMI was an observational, prospective study in 180 consecutive patients with AMI type 1 referred for primary percutaneous coronary intervention. On admission and at follow‐up visits (1 month, 1 year), 11‐dehydro‐TXB (2) was measured in urinary samples by using high‐performance liquid chromatography–tandem mass spectrometry. The primary outcome was occurrence of composite MACEs during 1‐year after AMI. Left ventricular ejection fraction was assessed in echocardiography on admission and at 1‐year follow‐up. Analyses of 11‐dehydro‐TXB (2) (pg/mg creatinine) were performed on log‐transformed data and expressed as median with IQR (Q1–Q3). 11‐Dehydro‐TXB (2) level on admission was 7.39 (6.85–8.01) and decreased at 1 month (6.73, 6.27–7.12; P<0.001) and 1‐year follow‐up (6.37, 5.91–6.94; P<0.001). In univariate analysis, baseline 11‐dehydro‐TXB (2) was higher in patients with MACEs (n=60; 7.73, 7.07–8.60) compared with those without MACEs (n=119; 7.28, 6.68–7.79; P=0.002). In multivariate regression model, 11‐dehydro‐TXB (2) and 3 other variables (diabetes, multivessel disease, and left ventricular ejection fraction) were found to be best 1‐year cumulative MACE predictors with odds ratio for 11‐dehydro‐TXB (2) of 1.58 (95% CI 1.095–2.33; P=0.017) and area under the curve (in receiver operating characteristic analysis of 0.8). Baseline 11‐dehydro‐TXB (2) negatively correlated with both left ventricular ejection fraction on admission (R=−0.21; P=0.006) and after 1 year (R=−0.346; P<0.001). CONCLUSIONS: 11‐Dehydro‐TXB (2) predicts 1‐year cumulative MACEs in AMI patients and provides prognostic information on the left ventricular performance

Leukotriene biosynthesis in coronary artery disease : results of the Leukotrienes and Thromboxane In Myocardial Infarction (LTIMI) study

Leukotrienes (LTs) may be involved in atherosclerosis and may contribute to cardiovascular outcomes in CAD. We aimed to compare the baseline LT production in patients with stable CAD (sCAD) and myocardial infarction (MI), and to assess whether an increased LT production is associated with major adverse cardiovascular events (MACEs) at 1 year after MI. LTIMI (Leukotrienes and Thromboxane In Myocardial Infarction) was a single‑center, prospective, observational study of patients with stable sCAD and MI. Urinary leukotriene $E_{4}$ ($LTE_{4}$) levels were measured on admission, at 1 month, and at 1 year, using high‑performance liquid chromatography tandem mass spectrometry. Of the 404 patients screened, 289 were enrolled (110 with sCAD and 179 with MI; mean [SD] age, 63.9 [$^{10.9]}$ years). Patients with MI had higher median (interquartile range [IQR]) levels of log‑transformed $LTE_{4}$ ($logLTE_{4}$) than those with sCAD (4.74 pg/mg creatinine [$^{4_5.45]}$ vs 4.51 pg/mg creatinine [3.99=4.86], respectively; P <0.001). Median (IQR) $logLTE_{4}$ levels in patients with MI significantly decreased at 1 month to 4.37 pg/mg creatinine (3.81-4.95), and at 1 year to 4.16 pg/mg creatinine (3.55-4.85). The baseline urinary $logLTE_{4}$ levels were similar in patients with MACEs and those without MACEs (median [IQR], 4.78 pg/mg creatinine [4.01-5.56]) and 4.68 pg/mg creatinine [3.97-5.28], respectively; P >0.05). Multiple regression showed no relation between $LTE_{4}$ levels and the incidence of MACEs. LT production assessed by urinary $LTE_{4}$ excretion is higher in patients with MI than in those with sCAD; however, $LTE_{4}$ levels at baseline do not differ between patients with and without MACEs at 1 year after MI

Higher order moment models of dense stellar systems: Applications to the modeling of the stellar velocity distribution function

Dense stellar systems such as globular clusters, galactic nuclei and nuclear star clusters are ideal loci to study stellar dynamics due to the very high densities reached, usually a million times higher than in the solar neighborhood; they are unique laboratories to study processes related to relaxation. There are a number of different techniques to model the global evolution of such a system. In statistical models we assume that relaxation is the result of a large number of two-body gravitational encounters with a net local effect. We present two moment models that are based on the collisional Boltzmann equation. By taking moments of the Boltzmann equation one obtains an infinite set of differential moment equations where the equation for the moment of order $n$ contains moments of order $n+1$. In our models we assume spherical symmetry but we do not require dynamical equilibrium. We truncate the infinite set of moment equations at order $n=4$ for the first model and at order $n=5$ for the second model. The collisional terms on the right-hand side of the moment equations account for two-body relaxation and are computed by means of the Rosenbluth potentials. We complete the set of moment equations with closure relations which constrain the degree of anisotropy of our model by expressing moments of order $n+1$ by moments of order $n$. The accuracy of this approach relies on the number of moments included from the infinite series. Since both models include fourth order moments we can study mechanisms in more detail that increase or decrease the number of high velocity stars. The resulting model allows us to derive a velocity distribution function, with unprecedented accuracy, compared to previous moment models.Comment: Accepted for publication by MNRAS after minor correction

Collapse and Fragmentation of Rotating Magnetized Clouds. I. Magnetic Flux - Spin Relation

We discuss evolution of the magnetic flux density and angular velocity in a molecular cloud core, on the basis of three-dimensional numerical simulations, in which a rotating magnetized cloud fragments and collapses to form a very dense optically thick core of > 5 times 10 ^10 cm^-3 . As the density increases towards the formation of the optically thick core, the magnetic flux density and angular velocity converge towards a single relationship between the two quantities. If the core is magnetically dominated its magnetic flux density approaches 1.5 (n/5 times 10^10 cm^-3)^1/2 mG, while if the core is rotationally dominated the angular velocity approaches 2.57 times 10^-3, (n/5 times 10^10 cm^-3)^1/2 yr^-1, where n is the density of the gas. We also find that the ratio of the angular velocity to the magnetic flux density remains nearly constant until the density exceeds 5 times 10^10 cm^-3. Fragmentation of the very dense core and emergence of outflows from fragments are shown in the subsequent paper.Comment: 17 pages, 12 figures, accepted for publication in MNRA

Monte Carlo simulations of star clusters -- III. A million body star cluster

A revision of Stodolkiewicz's Monte Carlo code is used to simulate the evolution of million body star clusters. The new method treats each superstar as a single star and follows the evolution and motion of all individual stellar objects. A survey of the evolution of N-body systems influenced by the tidal field of a parent galaxy and by stellar evolution is presented. The process of energy generation is realized by means of appropriately modified versions of Spitzer's and Mikkola's formulae for the interaction cross section between binaries and field stars and binaries themselves. The results presented are in good agreement with theoretical expectations and the results of other methods. During the evolution, the initial mass function (IMF) changes significantly. The local mass function (LMF) around the half--mass radius closely resembles the actual global mass function (GMF). At the late stages of evolution the mass of the evolved stars inside the core can be as high as 97% of the total mass in this region. For the whole system, the evolved stars can compose up to 67% of the total mass. The evolution of cluster anisotropy strongly depends on initial cluster concentration, IMF and the strength of the tidal field. The results presented are the first step in the direction of simulating the evolution of real globular clusters by means of the Monte Carlo method.Comment: 12 pages, 11 figure