Multiple cyclotron line-forming regions in GX 301-2

We present two observations of the high-mass X-ray binary GX 301-2 with NuSTAR, taken at different orbital phases and different luminosities. We find that the continuum is well described by typical phenomenological models, like a very strongly absorbed NPEX model. However, for a statistically acceptable description of the hard X-ray spectrum we require two cyclotron resonant scattering features (CRSF), one at ~35 keV and the other at ~50 keV. Even though both features strongly overlap, the good resolution and sensitivity of NuSTAR allows us to disentangle them at >=99.9% significance. This is the first time that two CRSFs are seen in GX 301-2. We find that the CRSFs are very likely independently formed, as their energies are not harmonically related and, if it were a single line, the deviation from a Gaussian shape would be very large. We compare our results to archival Suzaku data and find that our model also provides a good fit to those data. We study the behavior of the continuum as well as the CRSF parameters as function of pulse phase in seven phase bins. We find that the energy of the 35 keV CRSF varies smoothly as function of phase, between 30-38 keV. To explain this variation, we apply a simple model of the accretion column, taking the altitude of the line-forming region, the velocity of the in-falling material, and the resulting relativistic effects into account. We find that in this model the observed energy variation can be explained simply due to a variation of the projected velocity and beaming factor of the line forming region towards us.Comment: 18 pages, 10 figures, accepted for publication in A&

A Probabilistic Analysis of Kademlia Networks

Kademlia is currently the most widely used searching algorithm in P2P (peer-to-peer) networks. This work studies an essential question about Kademlia from a mathematical perspective: how long does it take to locate a node in the network? To answer it, we introduce a random graph K and study how many steps are needed to locate a given vertex in K using Kademlia's algorithm, which we call the routing time. Two slightly different versions of K are studied. In the first one, vertices of K are labelled with fixed IDs. In the second one, vertices are assumed to have randomly selected IDs. In both cases, we show that the routing time is about c*log(n), where n is the number of nodes in the network and c is an explicitly described constant.Comment: ISAAC 201

Associations of cardiac structure with obesity, blood pressure, inflammation, and insulin resistance in African-American adolescents.

To determine if obesity, blood pressure (BP), markers of inflammation, and insulin resistance are associated with cardiac structure in African-American adolescents, a cross-sectional study was performed on a cohort oversampled for high BP and obesity. Measurements included the following: anthropometrics, BP, homeostasis model assessment (HOMA) to assess insulin resistance, high-sensitivity C-reactive protein, and plasma adipokines (adiponectin, interleukin-6, plasminogen activator inhibitor-1). Echocardiogram measurements were left-ventricular mass index (LVMI) (g/m(2.7)), LV relative wall thickness (LVRWT), left-atrial diameter index [LADI (mm/m)], and LV diastolic time intervals. LADI (r (2) = 0.25) was associated with body mass index (BMI) systolic BP (SBP) and female sex. LVMI (r (2) = 0.35) variation was associated with BMI SBP, heart rate, age, and male sex. LVRWT (r (2) = 0.05) was associated with HOMA. Tissue diastolic intervals were not associated with any risk factor. Inflammatory markers and adipokines were associated with BMI but were not independently associated with any echocardiographic measures. In African-American adolescents, BMI and SBP, but not inflammatory markers or adipokines, are important correlates of LA size and LVM

Unifying static and dynamic approaches to evolution through the Compliant Systems Architecture

©2004 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.Support for evolution can be classified as static or dynamic. Static evolvability is principally concerned with structuring systems as separated abstractions. Dynamic evolvability is concerned with the means by which change is effected. Dynamic evolution provides the requisite flexibility for application evolution, however, the dynamic approach is not scalable in the absence of static measures to achieve separation of abstractions. This separation comes at a price in that issues of concern become trapped within static abstraction boundaries, thereby inhibiting dynamic evolution. The need for a unified approach has long been recognised but existing systems that attempt to address this need do so in an ad-hoc manner. The principal reason for this is that these approaches fail to resolve the incongruence in the underlying models. Our contention is that this disparity is incidental rather than fundamental to the problem. To this end we propose an alternative model based on the Compliant Systems Architecture (CSA), a structuring methodology for constructing software systems. The overriding benefit of this work is increased flexibility. Specifically our contribution is an instantiation of the CSA that supports unified static and dynamic evolution techniques. Our model is explored through a worked example in which we evolve an application’s concurrency model.Falkner, K.; Detmold, H.; Howard, D.; Munro, D.S.; Morrison, R.; Norcross, S

Pensamentos em ação

Two musician sociologists asked themselves this question: how can four guys who have never met and who have no written music, meet, shake hands, and start playing in a way that sounds like they’ve been working together for years. Faulkner and Becker decided to answer this question with field research. Because they lived 3,000 miles apart they cooperated via e-mail, thus preserving a record of the creative scientific process as it really occurs.Key words: music, repertoire, fieldwork methods.Dois músicos sociólogos se fizeram a seguinte pergunta: como quatro caras que nunca se encontraram e que não têm nenhuma música escrita, apertam as mãos, e começam a tocar de uma forma que parece que eles estão trabalhando juntos há anos? Faulkner e Becker decidiram responder a pergunta com pesquisa de campo. Porque viviam a 3.000 milhas de distância eles cooperaram via email, preservando, assim, um registro do processo científico criativo como ele realmente ocorre.Palavras-chave: música, repertório, métodos depesquisa de campo

A double-blind randomized trial of fish oil to lower triglycerides and improve cardiometabolic risk in adolescents.

OBJECTIVES: To determine the efficacy of 4 g/day fish oil to lower triglycerides and impact lipoprotein particles, inflammation, insulin resistance, coagulation, and thrombosis. STUDY DESIGN: Participants (n = 42, age 14 ± 2 years) with hypertriglyceridemia and low-density lipoprotein (LDL) cholesterol/dL were enrolled in a randomized, double-blind, crossover trial comparing 4 g of fish oil daily with placebo. Treatment interval was 8 weeks with a 4-week washout. Lipid profile, lipoprotein particle distribution and size, glucose, insulin, high-sensitivity C-reactive protein, interleukin-6, fibrinogen, plasminogen activator inhibitor-1, and thrombin generation were measured. RESULTS: Baseline lipid profile was total cholesterol 194 (5.4) mg/dL (mean [SE]), triglycerides 272 (21) mg/dL, high-density lipoprotein cholesterol 39 (1) mg/dL, and LDL cholesterol 112 (3.7) mg/dl. LDL particle number was 1614 (60) nmol/L, LDL size was 19.9 (1.4) nm, and large very low-density lipoprotein/chylomicron particle number was 9.6 (1.4) nmol/L. Triglycerides decreased on fish oil treatment but the difference was not significant compared with placebo (-52 ± 16 mg/dL vs -16 ± 16 mg/dL). Large very low-density lipoprotein particle number was reduced (-5.83 ± 1.29 nmol/L vs -0.96 ± 1.31 nmol/L; P \u3c .0001). There was no change in LDL particle number or size. There was a trend towards a lower prothrombotic state (lower fibrinogen and plasminogen activator inhibitor-1; .10 \u3e P \u3e .05); no other group differences were seen. CONCLUSIONS: In children, fish oil (4 g/day) lowers triglycerides slightly and may have an antithrombotic effect but has no effect on LDL particles

Formation of phase lags at the cyclotron energies in the pulse profiles of magnetized, accreting neutron stars

Context: Accretion-powered X-ray pulsars show highly energy-dependent and complex pulse-profile morphologies. Significant deviations from the average pulse profile can appear, in particular close to the cyclotron line energies. These deviations can be described as energy-dependent phase lags, that is, as energy-dependent shifts of main features in the pulse profile. Aims: Using a numerical study we explore the effect of cyclotron resonant scattering on observable, energy-resolved pulse profiles. Methods: We generated the observable emission as a function of spin phase, using Monte Carlo simulations for cyclotron resonant scattering and a numerical ray-tracing routine accounting for general relativistic light-bending effects on the intrinsic emission from the accretion columns. Results: We find strong changes in the pulse profile coincident with the cyclotron line energies. Features in the pulse profile vary strongly with respect to the average pulse profile with the observing geometry and shift and smear out in energy additionally when assuming a non-static plasma. Conclusions: We demonstrate how phase lags at the cyclotron energies arise as a consequence of the effects of angular redistribution of X-rays by cyclotron resonance scattering in a strong magnetic field combined with relativistic effects. We also show that phase lags are strongly dependent on the accretion geometry. These intrinsic effects will in principle allow us to constrain a system's accretion geometry.Comment: 4 pages, 4 figures; updated reference lis