Does gentrification of the Praga Północ district in Warsaw really exist?

Research on gentrification has been conducted for over 50 years by representatives of many disciplines. Modern gentrification is a process somewhat different from that originally described by R. Glass in 1964. Authors do not agree how to measure the process, nor how to explain its meaning (Bourne, 1993). Creating the right indicators is very difficult, especially if it is widely believed that gentrification, as a process identifying changes over time and a way of measuring dynamics, should enable the comparison of data from multiple years (Lees, 2010). The aim of this study was to identify the socio-spatial changes taking place in the Warsaw district of Praga Północ and to determine if it can be described as gentrification. The study area is a district stereotypically perceived as neglected, dangerous and deteriorated (e.g. Dudek-Mańkowska, 2011), at the same time subject to strong functional changes. Praga Północ is also an area of interest to many artists, creative industries and developers, and is undergoing gradual regeneration through municipal urban revitalization programs. It is also an area that the media portray as undergoing the process of gentrification. The results show that social and residential changes actually take place but the overall gentrification has not been felt by residents

All non-trivial variants of 3-LDT are equivalent

The popular 3-SUM conjecture states that there is no strongly subquadratic time algorithm for checking if a given set of integers contains three distinct elements that sum up to zero. A closely related problem is to check if a given set of integers contains distinct $x_1, x_2, x_3$ such that $x_1+x_2=2x_3$. This can be reduced to 3-SUM in almost-linear time, but surprisingly a reverse reduction establishing 3-SUM hardness was not known. We provide such a reduction, thus resolving an open question of Erickson. In fact, we consider a more general problem called 3-LDT parameterized by integer parameters $\alpha_1, \alpha_2, \alpha_3$ and $t$. In this problem, we need to check if a given set of integers contains distinct elements $x_1, x_2, x_3$ such that $\alpha_1 x_1+\alpha_2 x_2 +\alpha_3 x_3 = t$. For some combinations of the parameters, every instance of this problem is a NO-instance or there exists a simple almost-linear time algorithm. We call such variants trivial. We prove that all non-trivial variants of 3-LDT are equivalent under subquadratic reductions. Our main technical contribution is an efficient deterministic procedure based on the famous Behrend's construction that partitions a given set of integers into few subsets that avoid a chosen linear equation

Space dependent mean field approximation modelling

C. Zerafa and R. Cauchi acknowledge the support of the Strategic Educational Pathways Scholarship Scheme (Malta). These STEPS scholarships are part-financed by the European Union European Social Fund. B. Zapotoczny thanks for the PhD grant under Sub-Action 8.2.2 Regional Innovation Strategies, Activity 8.2 Know-How Transfer, Priority VIII Regional Business Personnel of the Human Capital Operational Programme, co-funded from the EU resources within the European Social Fund as well as the state budget and the Lubuskie Voivodship.It is shown that the self-consistency condition which is the basic equation for calculating the mean-field order parameter of any mean-field model Hamiltonian can be replaced by the standard Metropolis Monte Carlo scheme. The advantage of this method is its ease of implementation for both the homogeneous mean-field order parameter and the heterogeneous one. To be specific, the mean-field version of the Ising model spin system is discussed in detail and the resulting magnetization is the same as in the case of solving the respective mean-field self-consistency equation. In addition, it is shown that if a high temperature phase of such system is quenched below critical temperature then the mean field experienced by spins develops into a network of domains in analogous way as it happens with the spins in the case of the exact many-body Hamiltonian system and the coarsening processes start to take place. To show that the introduced Metropolis Monte Carlo method works also in case of the continuous variables the order parameter for the Maier-Saupe model for nematic liquid crystals has been calculated.peer-reviewe

Effect of day- and night-time admissions on long-term clinical outcomes of patients with acute myocardial infarction treated with percutaneous coronary intervention

INTRODUCTION It has been suggested that the time of admission during the day and night may influence the clinical outcomes of patients with acute myocardial infarction (AMI) treated with percutaneous coronary intervention (PCI). OBJECTIVES The aim of this study was to assess the impact of day- and night‑time admissions on the clinical outcomes of patients with AMI undergoing PCI. PATIENTS AND METHODS This retrospective cohort study was based on the data on PCIs performed in Poland from January 2014 to December 2017, prospectively collected in the National Registry of Invasive Cardiology Procedures (ORPKI). Day hours were defined as the time interval between 7:00 am and 10:59 pm. The study endpoints included the all‑cause in‑hospital mortality rate and major adverse cardiovascular and cerebrovascular events (MACCEs) at 30‑day, 12‑month, and 36‑month follow‑up. RESULTS A total of 2919 patients were included in the study (2462 [84.3%] treated during the day hours). ST‑segment elevation myocardial infarction (1993 [68.3%]) was the main indication for PCI. We demonstrated that the 30‑day mortality rate was significantly higher in patients treated during the night hours than during the day hours (P = 0.01). Night hours were also among the independent predictors of increased 30‑day mortality (hazard ratio, 1.54; 95% CI, 1.11–2.16; P = 0.01). No significant differences were observed in in‑hospital, 12‑month, and 36‑month mortality rates between patients treated during the night and day hours. There were no significant differences in the MACCE rates at the follow‑up timepoints. CONCLUSIONS Primary PCI for AMI is associated with increased 30‑day mortality among patients treated during the night hours compared with those managed during the day hours