Direct epitaxial growth of polar Hf0.5 Zr0.5 O2 films on corundum

Single-phase epitaxial Hf0.5 Zr0.5 O2 films with non-centrosymmetric orthorhombic structure have been grown directly on electrode-free corundum (a-Al2 O3) substrates by pulsed laser deposition. A combination of high-resolution X-ray diffraction and X-ray absorption spectroscopy confirms the epitaxial growth of high-quality films belonging to the Pca21 space group, with 111] out-of-plane orientation. The surface of a 7-nm-thick sample exhibits an atomic step-terrace structure with a corrugation of the order of one atomic layer, as proved by atomic force microscopy. Scanning transmission electron microscopy reveals that it consists of grains with around 10 nm lateral size. The polar nature of this film has been corroborated by pyroelectric measurements. These results shed light on the mechanisms of the epitaxial stabilization of the ferroelectric phase of hafnia. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Integer part independent polynomial averages and applications along primes

Exploiting the equidistribution properties of polynomial sequences, following the methods developed by Leibman (2005) and Frantzikinakis (2009, 2010), we show that the ergodic averages with iterates given by the integer parts of strongly independent real valued polynomials converge in the mean to the expected limit. These results have, via Furstenberg’s correspondence principle, immediate combinatorial applications, while combining these results with methods of Frantzikinakis et al. (2013) and Koutsogiannis (2018) we get the expected limits and combinatorial results for multiple averages for a single sequence, as well as for several sequences along prime numbers. © Instytut Matematyczny PAN, 201

The Iraq war as curricular knowledge:From the political to the pedagogic divide

The paper deals with educational discourse concerning the recent Iraq war in an attempt to explore how broader political issues, such as the Iraq war, are materialised in everyday classroom practices. It analyses lesson plans, aimed to be used by US educators of primary and secondary schools, from two Internet sites: one supporting the official position of US to go to war and the other taking a position against the war. The paper suggests that the lesson plans in the two sites constitute materialisations of two general approaches to education, the dominant and the critical, which do not simply adopt opposing views concerning the war but which, most importantly, contribute to the construction of different pedagogic subjects: in one case, there is an attempt towards ‘compulsory patriotism’, whereas in the other an attempt towards a ‘compulsory’ challenging of the war. The ideals which are in fact recontextualised here are that of nation and justice, the pedagogisation of which seems to raise much more questions than to provide answers. © 2005 John Benjamins Publishing Company

Recent climate trends over Greece

Temperature and humidity play a key role in climate change assessment. This study focuses on the analysis of surface and upper-air temperature and humidity trends for a domain centered over the Greek region in the Eastern Mediterranean. The main purpose of this work is to investigate whether possible changes in the climate of the greater Greek region exist over the recent years. ERA-Interim reanalysis, surface and radiosonde observational data of air temperature, specific and relative humidity are used for a 39-year period (1979–2017). Through the spatial distribution of their trends, at different atmospheric pressure levels and seasons, it is possible to detect statistically significant spatial and temporal changes in the troposphere and stratosphere above the examined domain. Statistically significant warming trends at the 99% level are found at the surface over land and at the 95% level over sea during spring and summer for Greece; less pronounced and more sparsely distributed trends are identified during autumn and winter. Additionally, positive trends prevail throughout the entire extent of the troposphere, more pronounced during summer, whereas the stratosphere is characterized by negative trends. Trends derived from the reanalysis and observational data exhibit high degree of correlation both at surface and at upper atmospheric levels. In accordance, specific humidity has generally increased in the lower troposphere. Relative humidity time series demonstrate trends, which vary seasonally and geographically, due to its relationship with specific humidity and temperature. © 2019 Elsevier B.V

Multifractal Detrended Fluctuation Analysis of temperature reanalysis data over Greece

The Multifractal Detrended Fluctuation Analysis (MF-DFA) is used to examine the scaling behavior and the multifractal characteristics of the mean daily temperature time series of the ERA-Interim reanalysis data for a domain centered over Greece. The results showed that the time series from all grid points exhibit the same behavior: they have a positive long-term correlation and their multifractal structure is insensitive to local fluctuations with a large magnitude. Special emphasis was given to the spatial distribution of the main characteristics of the multifractal spectrum: the value of the Hölder exponent, the spectral width, the asymmetry, and the truncation type of the spectra. The most interesting finding is that the spatial distribution of almost all spectral parameters is decisively determined by the land-sea distribution. The results could be useful in climate research for examining the reproducibility of the nonlinear dynamics of reanalysis datasets and model outputs. © 2019 by the authors