Random barrier double-well model for resistive switching in tunnel barriers

The resistive switching phenomenon in MgO-based tunnel junctions is attributed to the effect of charged defects inside the barrier. The presence of electron traps in the MgO barrier, that can be filled and emptied, locally modifies the conductance of the barrier and leads to the resistive switching effects. A double-well model for trapped electrons in MgO is introduced to theoretically describe this phenomenon. Including the statistical distribution of potential barrier heights for these traps leads to a power-law dependence of the resistance as a function of time, under a constant bias voltage. This model also predicts a power-law relation of the hysteresis as a function of the voltage sweep frequency. Experimental transport results strongly support this model and in particular confirm the expected power laws dependencies of resistance. They moreover indicate that the exponent of these power laws varies with temperature as theoretically predicted.Comment: 18 pages, 5 figures, final versio

Study of molecular spin-crossover complex Fe(phen)2(NCS)2 thin films

We report on the growth by evaporation under high vacuum of high-quality thin films of Fe(phen)2(NCS)2 (phen=1,10-phenanthroline) that maintain the expected electronic structure down to a thickness of 10 nm and that exhibit a temperature-driven spin transition. We have investigated the current-voltage characteristics of a device based on such films. From the space charge-limited current regime, we deduce a mobility of 6.5x10-6 cm2/V?s that is similar to the low-range mobility measured on the widely studied tris(8-hydroxyquinoline)aluminium organic semiconductor. This work paves the way for multifunctional molecular devices based on spin-crossover complexes

Characterization of the newly isolated lytic bacteriophages KTN6 and KT28 and their efficacy against Pseudomonas aeruginosa biofilm

We here describe two novel lytic phages, KT28 and KTN6, infecting Pseudomonas aeruginosa, isolated from a sewage sample from an irrigated field near Wroclaw, in Poland. Both viruses show characteristic features of Pbunalikevirus genus within the Myoviridae family with respect to shape and size of head/tail, as well as LPS host receptor recognition. Genome analysis confirmed the similarity to other PB1-related phages, ranging between 48 and 96%. Pseudomonas phage KT28 has a genome size of 66,381 bp and KTN6 of 65,994 bp. The latent period, burst size, stability and host range was determined for both viruses under standard laboratory conditions. Biofilm eradication efficacy was tested on peg-lid plate assay and PET membrane surface. Significant reduction of colony forming units was observed (70-90%) in 24 h to 72 h old Pseudomonas aeruginosa PAO1 biofilm cultures for both phages. Furthermore, a pyocyanin and pyoverdin reduction tests reveal that tested phages lowers the amount of both secreted dyes in 48-72 h old biofilms. Diffusion and goniometry experiments revealed the increase of diffusion rate through the biofilm matrix after phage application. These characteristics indicate these phages could be used to prevent Pseudomonas aeruginosa infections and biofilm formation. It was also shown, that PB1-related phage treatment of biofilm caused the emergence of stable phage-resistant mutants growing as small colony variants

Production of L3 Vowels: Is it Possible to Separate them from L1 and L2 Sounds?

It is incontrovertible that acquisition of a sound system of a second language is always a complex phenomenon and presents a great challenge for L2 learners (e.g. Rojczyk, 2010a). There are numerous studies (e.g. Nowacka, 2010; Flege, 1991) which show that L2 learners whose first language has a scarce number of sounds, have problems to distinguish L2 sound categories and tend to apply their L1 segments to new contexts. It may be easily detectable in the case of vowels. There is abundance of studies examining L2 learners’ successes and failures in production of L1 and L2 vowels (e.g. Flege, 1992; Nowacka, 2010; Rojczyk, 2010a). Usually such projects show how difficult it is for L2 learners to separate “old” and “new” vowel categories. However, the situation becomes much more complicated when we think of third language (L3) production. While in the case of L2 segmental production the number of factors affecting L2 sounds is rather limited (either interference from learners’ L1 or some kind of L2 intralingual influence), in the case of L3 segmental production we may encounter L1→L3, L2→L3 or L3 intralingual interference. This makes separation of L3 sounds a much more complex process. The aim of this study is to examine whether speakers of L1 Polish, L2 English and L3 German are able to separate new, L3 vowel categories from their native and L2 categories. Being a part of a larger project, this time the focus is on German /œ/. This vowel was chosen since it is regarded as especially difficult for Polish learners of German and it is frequently substituted with some other sounds. A group of English philology (Polish-English-German translation and interpretation programme) students was chosen to participate in this project. They were advanced speakers of English who did not encounter any difficulties in communication with native speakers of this language and upper-intermediate users of German. They had been taught both English and German pronunciation/practical phonetics during their studies at the University of Silesia. The subjects were asked to produce words containing analysed vowels, namely: P /u/, P /ɔ/, P /ɛ/, E /u/, E /ɔ / and G /œ/. All examined vowels were embedded in a /bVt/ context. The target /bVt/ words were then embedded in carrier sentences I said /bVt/ this time in English, Ich sag’ /bVt/ diesmal in German and Mówię /bVt/ teraz in Polish, in a non-final position. The sentences were presented to subjects on a computer screen and the produced chunks were stored in a notebook’s memory as .wav files ready for inspection. The Praat 5.3.12 speech-analysis software package (Boersma, 2001) was used to scroll through the audio files in order to locate an onset and offset of target vowels, measure the F1 and F2 frequencies and plot vowels on the plane. All analyses were also performed using Praat. The obtained results shed new light on L3 segmental production and L1 and L2 interference

Gender differences in language acquisition and learning

The present article was selected by me for inclusion in this volume as it discusses the issues connected with gender differences in language acquisition and learning that have been the major concern of my academic research over the past years. The article presents an overview of well‑known studies on gender as well as those not generally known. I also report in this article on my contribution to this area of research on language acquisition. The issue of gender is discussed here from psycholinguistic, neurolinguistic and sociolinguistic perspectives

A proposed integrated approach for the preclinical evaluation of phage therapy in Pseudomonas infections

Bacteriophage therapy is currently resurging as a potential complement/alternative to antibiotic treatment. However, preclinical evaluation lacks streamlined approaches. We here focus on preclinical approaches which have been implemented to assess bacteriophage efficacy against Pseudomonas biofilms and infections. Laser interferometry and profilometry were applied to measure biofilm matrix permeability and surface geometry changes, respectively. These biophysical approaches were combined with an advanced Airway Surface Liquid infection model, which mimics in vitro the normal and CF lung environments, and an in vivo Galleria larvae model. These assays have been implemented to analyze KTN4 (279,593 bp dsDNA genome), a type-IV pili dependent, giant phage resembling phiKZ. Upon contact, KTN4 immediately disrupts the P. aeruginosa PAO1 biofilm and reduces pyocyanin and siderophore production. The gentamicin exclusion assay on NuLi-1 and CuFi-1 cell lines revealed the decrease of extracellular bacterial load between 4 and 7 logs and successfully prevents wild-type Pseudomonas internalization into CF epithelial cells. These properties and the significant rescue of Galleria larvae indicate that giant KTN4 phage is a suitable candidate for in vivo phage therapy evaluation for lung infection applications

Acquiring meaning of foreign vocabulary

Artykuł traktuje o przyswajaniu znaczenia słów obcojęzycznych, jako jednego z elementów przyswajaniasłownictwa obcojęzycznego. Jest to więc przyswajanie mówionej raczej niż pisanej formysłowa wraz z jego znaczeniem. Proces ten przebiega etapami; poprzez połączenie struktury fonologicznejze strukturą semantyczną, a następnie zapamiętanie tego związku, przechowanie gow pamięci i wydobycie go z pamięci. Poszczególne etapy przyswajania słownictwa zostały omówionepo kolei. Główny nacisk położono na techniki zapamiętywania obcojęzycznej struktury,która – jak w przypadku nazwiska – trudna jest do zapamiętywania, gdyż – tak jak nazwiska – nietworzy skojarzeń, nie ma bowiem znaczenia. Techniki tworzenia skojarzeń, służące zapamiętywaniui wydobywaniu z pamięci, omówiono wraz z objaśnieniem procesów skojarzeniowych. Mowatu o procesach skojarzeniowych interjęzykowych, które występują przy zapamiętywaniu wyrazówobcojęzycznych

Control of defect-mediated tunneling barrier heights in ultrathin MgO films

The impact of oxygen vacancies on local tunneling properties across rf-sputtered MgO thin films was investigated by optical absorption spectroscopy and conducting atomic force microscopy. Adding O$_2$ to the Ar plasma during MgO growth alters the oxygen defect populations, leading to improved local tunneling characteristics such as a lower density of current hotspots and a lower tunnel current amplitude. We discuss a defect-based potential landscape across ultrathin MgO barriers.Comment: 4 pages, 4 figure

Gender differences in language acquisition and learning

W rozdziale zaprezentowano przegląd badań z zakresu różnic w przyswajaniu języka drugiego i obcego przez kobiety i mężczyzn. Wyniki pierwszych badań w tej dziedzinie wskazywały na przewagę kobiet, uzasadniając ją różnicami biologicznymi oraz poznawczymi między przedstawicielami obydwu płci. Kobiety, u których częściej występuje dominacja lewej półkuli mózgu, przejawiają większe zdolności językowe niż mężczyźni, u których częściej występuje dominacja prawopółkulowa. Również w procesie ewolucji kobiety jako matki lepiej wykształciły sprawności językowe. Późniejsze badania, uwzględniające nowe metody i interpretacje, nie potwierdzają takich różnic między przedstawicielami obydwu płci. Rozdział zawiera opis dwóch badań przeprowadzonych przez Autora. Pierwsze z nich dotyczyło różnic między dziewczętami a chłopcami w wieku licealnym w zakresie stosowania strategii uczenia się, drugie natomiast percepcji obcojęzycznych głosek wśród dzieci w wieku przedszkolnym. Przykładem nowej metodologii stosowanej przy interpretacji różnic między kobietami a mężczyznami w przyswajaniu języka obcego są badania dotyczące nauki czytania w języku obcym przeprowadzone wśród młodzieży szkolnej (w wieku 15 lat). Wykazano w nich, że różnice dotyczą nie samej płci, lecz jej immanentnych cech, np. gustów literackich, stosunku do czytania, korzystania z komputera itp. Cechy te korelują ze skutecznością rozwijania sprawności czytania w języku obcym