Discrete breathers in thermal equilibrium: distributions and energy gaps

We study a discrete two-dimensional nonlinear system that allows for discrete breather solutions. We perform a spectral analysis of the lattice dynamics at thermal equilibrium and use a cooling technique to measure the amount of breathers at thermal equilibrium. Our results confirm the existence of an energy threshold for discrete breathers. The cooling method provides with a novel computational technique of measuring and analyzing discrete breather distribution properties in thermal equilibrium.Comment: 20 pages, 14 figure

The purchasing power parity fallacy: time to reconsider the PPP hypothesis

This is a post-peer-review, pre-copyedit version of an article published in Open Economic Reviews. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11079-017-9473-9Traded good prices affect the real exchange rate first through their effect on the overall price level and second through their effect on the nominal exchange rate. Whereas the price level effect, which is positive in sign, is universally recognized, the nominal exchange rate effect, which is negative in sign, is routinely ignored. We calculate to which extent real exchange rate changes are accounted for by traded good prices and other components of the real exchange rate. We find that the nominal exchange rate effect neutralizes the price level effect entirely, suggesting that, contrary to popular belief, good market arbitrage is not conducive to purchasing power parity (the purchasing power parity fallacy). Rather than traded or non-traded good prices, the main driving force behind the real exchange rate is currency market pressure, a variable that, as we argue, is largely determined by the cumulative trade and capital flows of a countr

Dissipative breathers in rf SQUID metamaterials

The existence and stability of dissipative breathers in rf SQUID (Superconducting Quantum Interference Device) arrays is investigated numerically. In such arrays, the nonlinearity which is intrinsic to each SQUID, along with the weak magnetic coupling of each SQUID to its nearest neighbors, result in the formation of discrete breathers. We analyze several discrete breather excitations in rf SQUID arrays driven by alternating flux sources in the presence of losses. The delicate balance between internal power losses and input power, results in the formation of dissipative discrete breather (DDB) structures up to relatively large coupling parameters. It is shown that DDBs may locally alter the magnetic response of an rf SQUID array from paramagnetic to diamagnetic or vice versa.Comment: 5 pages, 4 figure

Monetary policy rules in the pre-EMU era: Is there a common rule?

Despite the great importance and final success of the convergence process that led to the establishment of the European Monetary Union, there is no clear agreement regarding the monetary policy pursued in the member countries during the convergence process. This paper contributes to the literature with an empirical analysis of the period from 1993 to 1998 that encompasses eleven EMU countries. In particular, Taylor type interest rate rules are estimated with monthly national data to find that, despite certain similarities and exceptions, the rule followed by each country is distinct and differs substantially from the standard Taylor rule. However, for most countries, the parameter estimates reflect the principles proclaimed by the monetary policy authorities and, in addition, it is shown that in most cases the estimated rules reproduce the policy setting quite closely. JEL Classification: E58, F41ERM, monetary policy, output gap, Taylor rule

The role of TET2 protein and oxidised forms of 5-methylcytosine in brain tumours

DNA methylation (5-methylcytosine, 5mC) is the major epigenetic modification involved in transcriptional regulation. Ten-eleven translocation (TET) proteins can enzymatically oxidise 5mC producing 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). According to several reports, 5hmC levels are reduced in human tumours; however, the distribution and the exact biological role of TET-dependent oxidation to 5fC and 5caC in cancers is poorly studied. Here, using a range of techniques including, immunocytochemistry, 2 dimensional ultra-performance liquid chromatography coupled with tandem mass-spectrometry (2D-UPLC–MS/MS) and CRISPR/Cas9 gene editing we studied the presence and the distribution of 5caC/5hmC in brain tumours cell lines. Our ultimate goal was to examine the role of TET2 in the oxidation of 5mC to 5hmC/5caC in glioblastoma multiforme (GBM) pathogenesis and the role of 5caC potential readers in the interpretation of active DNA demethylation in medulloblastoma (MB) (paediatric brain tumour) cell lines. We found that, while GBM cell lines exhibit low levels of 5hmC, they are, rather unexpectedly, characterised by detectable 5caC levels. Remarkably, 5caC content in GBM corresponds to elevated levels of TET2 transcript. We next used CRISPR/Cas9 to knockout (KO) TET2 in the LN18 GBM cell line. 5hmC levels were significantly reduced in TET2 KO cell line. Moreover, we showed significantly reduced tumorigenic ability of TET2 KO cells in parallel with the reduction of the transcript levels of key glial cancer stem cell markers. We also showed that SMARCC2 and RCOR2 transcription factors with unique roles in neurogenesis, are highly expressed in paediatric brain tumours, while their transient knockdown resulted at impaired 5caC levels in MB cell lines; indicating their role as 5caC readers. Our compiled data show the unique epigenetic signatures of adult and paediatric brain tumours, the role of TET2 in active DNA demethylation and its potential contribution to tumorigenesis

Surface magnetoinductive breathers in two-dimensional magnetic metamaterials

We study discrete surface breathers in two-dimensional lattices of inductively coupled split-ring resonators with capacitive nonlinearity. We consider both conservative (Hamiltonian) and analyze the properties of the modes localized in space and periodic in time (discrete breathers) located in the corners and on the edges of the lattice. We find that surface breathers in the Hamiltonian systems have lower energy than their bulk counterparts and they are generally more stable

Enhancing children’s early language and emergent literacy in a Greek pre-kindergarten heritage language classroom through a translingual and transcultural stance

Situated at the intersection of the emergent field of early heritage language education and pedagogy, this paper reports on a participatory action research project at a pre-kindergarten classroom in a Greek community school in Switzerland. Adopting a translingual and transcultural orientation to language and language learning, it scrutinizes the multilingual, multimodal, and multisensorial resources the children draw upon in their creative text-making and talk about texts and interrogates how these early language and emergent literacy practices open a space for children to articulate their agentive voices. It demonstrates that while emphasising Greek language learning, their other languages and lived experiences are listened to and honoured

Relationships between sixth grade students’ cognitive development and their collaborative processes during solving numerical puzzle Sudoku

Η παρούσα έρευνα μελετά τη σχέση που έχει η γνωστική ανάπτυξη στην επίλυση προβλημάτων σε δυάδες ή ατομικά, σε μαθητές έκτης δημοτικού με τη χρήση του αριθμητικού γρίφου Sudoku. Στόχος της μικτής αυτής έρευνας ήταν να διαφανεί αν οι μαθητές έχουν καλύτερα αποτελέσματα κατά την επίλυση του γρίφου Sudoku, όταν τοποθετηθούν σε ομοιογενείς ή ανομοιογενείς ομάδες. Συγκεκριμένα, τα ερωτήματα της έρευνας ήταν: πρώτο, ποιος τύπος δυάδας (ομοιογενής ή ανομοιογενής) είναι αποτελεσματικότερος, δεύτερο, όταν τα άτομα εργάζονται ατομικά ποιος τύπος γνωστικής ανάπτυξης επιφέρει τα καλύτερα δυνατά αποτελέσματα στην επίλυση του Sudoku και τρίτο, ποιος ήταν ο βαθμός συνεργασίας των δυάδων. Τα δύο πρώτα ερωτήματα απαντήθηκαν ποσοτικά, ενώ το τρίτο απαντήθηκε ποιοτικά. Στην έρευνα συμμετείχαν 220 μαθητές από 13 διαφορετικές τάξεις της έκτης δημοτικού συμπλήρωσαν το εργαλείο γνωστικής ανάπτυξης Group Assessment of Logical Thinking (GALT), που κατασκευάστηκε από τους Roadrangka, Yeany και Padilla (1983). Στη συνέχεια, 60 μαθητές επέλυσαν τον γρίφο Sudoku ατομικά και άλλοι 160 μαθητές τον έλυσαν σε δυάδες. Ένα από τα κύρια ευρήματα της έρευνας ήταν η μη ανάπτυξη συνεργασίας ανάμεσα στις δυάδες, με αποτέλεσμα οι επιδόσεις στην ατομική ικανότητα επίλυσης προβλήματος να μη διαφέρουν μεταξύ των ατόμων που εργάστηκαν ατομικά και των ατόμων που εργάστηκαν μέσα σε δυάδα στα αντίστοιχα επίπεδα γνωστικής ανάπτυξης.Collaborative learning is a subject that has occupied many researchers throughout the world. Many researchers have maintained that when students of all school stages, from kindergarten to higher education work in teams, this leads to high performance (Johnson, Skon, & Johnson, 1980), but also has a positive impact emotionally and psychologically (Schmitz & Winskel, 2008). However, there have been studies claiming that teamwork does not actually result in any substantive improvement in students’ efficiency (Samuelsson, 2010), or that only some students gain from this method of learning (Sears & Reagin, 2013). The present study explores how cognitive development relates to problem solving in pairs or individually, in students of the sixth grade in school using the numerical puzzle Sudoku. More specifically, the study explored four different types of pairs of two, according to the level of cognitive development (high – high, high – low, average – average and low – low) and three different types of units (high, average, low), all taken from sixth graders of a public elementary school. Additionally, the research studied whether solving Sudoku was more effective in pairs rather than individually. The sample of this research included thirteen sixth grade classes from a public elementary school in a city in Cyprus. The city was intentionally selected to facilitate the research. Two hundred twenty students completed the tool of cognitive development Group Assessment of Logical Thinking (GALT). Then, 60 students individually solved the Sudoku puzzle, while 160 students solved the puzzle in pairs. The results of the qualitative study showed that there were differences between the four types of pairs in terms of how they collaborated. Although students showed interest or even enthusiasm in solving the Sudoku puzzle, the majority of them did not work together so as to improve their performance. The results of the quantitative study confirmed that students failed to cooperate. The performance of the Individual Problem Solving Ability was not different among the four types of pairs. The majority of high-level cognitive development pairs started to solve the puzzle competitively. However, in the process they worked together to solve the puzzle correctly. They also behaved in an intensely self-centred way. In non-homogeneous pairs, low-performing students had a passive role in the group. Additionally, it seemed that the level of cooperation was related to high performance. The research demonstrated that students had difficulty in developing combinational thinking. This was the reason they could not solve the puzzle. Pairs did not cooperate, despite the fact that they had clear guidelines to do that. This finding should be a concern for teachers and the educational system of Cyprus, in general. The role of the teacher should be supportive in helping students overcome their difficulties, considering the theory of Vygotsky (2012) on systematic facilitating, development, and the Zone of Proximal Development