The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging

The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and is sensitive to large-scale and compact emission. It is, however, very challenging to synthesize thermal noise limited maps at full resolution, mainly because of the complexity of the low-frequency sky and the direction dependent effects (phased array beams and ionosphere). In this first paper of a series, we present a new calibration and imaging pipeline that aims at producing high fidelity, high dynamic range images with LOFAR High Band Antenna data, while being computationally efficient and robust against the absorption of unmodeled radio emission. We apply this calibration and imaging strategy to synthesize deep images of the Boötes and Lockman Hole fields at ∼150 MHz, totaling ∼80 and ∼100 h of integration, respectively, and reaching unprecedented noise levels at these low frequencies of .30 and .23 µJy beam−1 in the inner ∼3 deg2 . This approach is also being used to reduce the LOTSS-wide data for the second data release

Stellar dynamics in young clusters: the formation of massive runaways and very massive runaway mergers

In the present paper we combine an N-body code that simulates the dynamics of young dense stellar systems with a massive star evolution handler that accounts in a realistic way for the effects of stellar wind mass loss. We discuss two topics: 1. The formation and the evolution of very massive stars (with a mass >120 Mo) is followed in detail. These very massive stars are formed in the cluster core as a consequence of the successive (physical) collison of 10-20 most massive stars of the cluster (the process is known as runaway merging). The further evolution is governed by stellar wind mass loss during core hydrogen burning and during core helium burning (the WR phase of very massive stars). Our simulations reveal that as a consequence of runaway merging in clusters with solar and supersolar values, massive black holes can be formed but with a maximum mass of 70 Mo. In small metallicity clusters however, it cannot be excluded that the runaway merging process is responsible for pair instability supernovae or for the formation of intermediate mass black holes with a mass of several 100 Mo. 2. Massive runaways can be formed via the supernova explosion of one of the components in a binary (the Blaauw scenario) or via dynamical interaction of a single star and a binary or between two binaries in a star cluster. We explore the possibility that the most massive runaways (e.g., zeta Pup, lambda Cep, BD+433654) are the product of the collision and merger of 2 or 3 massive stars.Comment: Updated and final versio

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Fractal geometry of angular momentum evolution in near-Keplerian systems

In this Letter, we propose a method to study the nature of resonant relaxation in near-Keplerian systems. Our technique is based on measuring the fractal dimension of the angular momentum trails and we use it to analyse the outcome of N-body simulations. With our method, we can reliably determine the time-scale for resonant relaxation, as well as the rate of change of angular momentum in this regime. We find that growth of angular momentum is more rapid than random walk, but slower than linear growth. We also determine the presence of long-term correlations arising from the bounds on angular momentum growth. We develop a toy model that reproduces all essential properties of angular momentum evolution

Collisions Between Single Stars in Dense Clusters: Runaway Formation of a Massive Object

Using Monte Carlo codes, we follow the collisional evolution of clusters in a variety of scenarios. We consider the conditions under which a cluster of main-sequence stars may undergo rapid core collapse due to mass segregation, thus entering a phase of runaway collisions, forming a very massive star (VMS, M* > 1000Mo) through repeated collisions between single stars. Although collisional mass loss is accounted for realistically, we find that a VMS forms even in proto-galactic nuclei models with a high velocity dispersion (many 100 kms-1). Such a VMS may be a progenitor for an intermediate-mass black hole (M? >= 100Mo). In contrast, in galactic nuclei hosting a central massive black hole, collisions are found to be disruptive. The stars which are subject to collisions are progressively ground down by high-velocity collisions and a merger sequence appears impossible

In gesprek over methodieken rond diversiteit

NSVP - innovatiefinwerk.nl Auteurs: Daniel van Middelkoop, Gürkan Çelik, Ila Kasem, Lida van der Broek, Martha Meerman (red) Najat Bay, Olivia Andiel, Saskia Furrer Sonia Sjollema Samenvatting: Welke eisen stelt werken in een multiculturele omgeving aan professionals? Hoe kan integratie van arbeidsmigranten en vluchtelingen op een duurzame manier in organisaties plaatsvinden? Op welke manier kunnen ondernemers met een bi-culturele achtergrond hun innovatiekracht vergroten zodat ook de Nederlandse economie kan profiteren van de internationale netwerken die zij opbouwen? Het is een veelvoud van vragen op het snijvlak van organisatie en maatschappij waarvoor in de afgelopen jaren nieuwe methodieken zijn ontwikkeld, met financiële ondersteuning van de NSvP. Zo is een methodiek ontwikkeld om werkgevers te helpen om de kwaliteiten van vluchtelingen beter te onderkennen en te benutten, om het gesprek op gang te brengen om in onderwijs- en zorginstellingen de diversiteit in het primaire proces te begrijpen. Er is een project om jonge ondernemers met verschillende achtergronden meer met elkaar en met hun omgeving te verbinden. Het NSvP ondersteunde onderzoek naar Indiase verpleegkundigen die als arbeidsmigranten aan het werk gingen in een ziekenhuis. Het lijken allemaal zeer verschillende onderwerpen maar ze zijn allemaal gericht op het benutten van divers talent van werkende mensen

The role of azacitidine in the treatment of elderly patients with acute myeloid leukemia: Results of a retrospective multicenter study [Akut miyeloid lösemili yaşlı hastaların tedavisinde azasitidinin rolü: Retrospektif çok merkezli bir çalışmanın sonuçları]

PubMed ID: 27095141Objective: In this study, we aimed to investigate the efficacy and safety of azacitidine (AZA) in elderly patients with acute myeloid leukemia (AML), including patients with >30% bone marrow (BM) blasts. Materials and Methods: In this retrospective multicenter study, 130 patients of ?60 years old who were ineligible for intensive chemotherapy or had progressed despite conventional treatment were included. Results: The median age was 73 years and 61.5% of patients had >30% BM blasts. Patients received AZA for a median of four cycles (range: 1-21). Initial overall response [including complete remission (CR)/CR with incomplete recovery/partial remission] was 36.2%. Hematologic improvement (HI) of any kind was documented in 37.7% of all patients. HI was also documented in 27.1% of patients who were unresponsive to treatment. Median overall survival (OS) was 18 months for responders and 12 months for nonresponders (p=0.005). In the unresponsive patient group, any HI improved OS compared to patients without any HI (median OS was 14 months versus 10 months, p=0.068). Eastern Cooperative Oncology Group performance status of <2, increasing number of AZA cycles (?5 courses), and any HI predicted better OS. Age, AML type, and BM blast percentage had no impact. Conclusion: We conclude that AZA is effective and well tolerated in elderly comorbid AML patients, irrespective of BM blast count, and HI should be considered a sufficient response to continue treatment with AZA. © 2016, Turkish Society of Hematology. All rights reserved