Strain development and damage accumulation under ion irradiation of polycrystalline Ge-Sb-Te alloys

The atomic displacement produced by ion irradiation with 150 keV Ar+ ions has been studied in Ge1Sb2Te4 and Ge2Sb2Te5. Electrical, optical and structural measurements have been employed to characterize the induced electrical and structural modifications. At low temperature the amorphization threshold, evaluated by in situ reflectivity measurements, is independent of the composition and the crystalline structure, and it is equal to 1 x 1013 cm-2. At room temperature, at which dynamic annealing can take place, Ge2Sb2Te5 and Ge1Sb2Te4 in the rocksalt phase exhibit the same amorphization threshold (3 x 1013 cm-2). In the trigonal structure, instead, a higher fluence is required to amorphize the Ge1Sb2Te4, compared to Ge2Sb2Te5. The observed differences between the two compositions can be explained considering the effect of dynamic annealing during ion irradiation of the trigonal phase, which is characterized by the presence of van der Waals gaps. These may act as a preferential sink for the diffusion of the displaced atoms and the filling of these gaps tunes the electronic and structural properties. Filling of about 30% of the gaps produces an electronic transition from metallic to insulating behavior. By further increasing the disorder and filling more than 70% of the gaps the films convert into the rocksalt phase

Role of interfaces on the stability and electrical properties of Ge2Sb2Te5 crystalline structures

GeSbTe-based materials exhibit multiple crystalline phases, from disordered rocksalt, to rocksalt with ordered vacancy layers, and to the stable trigonal phase. In this paper we investigate the role of the interfaces on the structural and electrical properties of Ge2Sb2Te5. We find that the site of nucleation of the metastable rocksalt phase is crucial in determining the evolution towards vacancy ordering and the stable phase. By properly choosing the substrate and the capping layers, nucleation sites engineering can be obtained, thus promoting or preventing the vacancy ordering in the rocksalt structure or the conversion into the trigonal phase. The vacancy ordering occurs at lower annealing temperatures (170 °C) for films deposited in the amorphous phase on silicon (111), compared to the case of SiO2 substrate (200 °C), or in presence of a capping layer (330 °C). The mechanisms governing the nucleation have been explained in terms of interfacial energies. Resistance variations of about one order of magnitude have been measured upon transition from the disordered to the ordered rocksalt structure and then to the trigonal phase. The possibility to control the formation of the crystalline phases characterized by marked resistivity contrast is of fundamental relevance for the development of multilevel phase change data storage

Sinteza i antihipoksično djelovanje alifatskih i arilalifatskih amida kofein-8-tioglikolne kiseline

The synthesis of some aliphatic and arylaliphatic amides of caffeine-8-thioglycolic acid was studied. The structures of synthesized compounds were proved by microanalyses, IR- and 1H NMR data. Values of acute p.o. and i.p. toxicity in mice show lower toxicity compared to caffeine. Declines in spontaneous locomotor activity support the idea of depressive CNS activity of the compounds. Two compounds exhibited brain antihypoxic activity (5a and 5b against haemic and circulatory hypoxia, respectively).U radu je opisana sinteza alifatskih i arilalifatskih amida kofein-8-tioglikolne kiseline i njihova karakterizacija elementarnom analizom, IR- i 1H NMR spektroskopijom. Testiranja na miševima pokazuju da su sintetizirani spojevi primijenjeni p.o. i i.p. manje toksični od kofeina. Smanjenje lokomotoričke aktivnosti podupire ideju o njihovom depresivnom djelovanju na SŽS. Spojevi 5a i 5b djeluju antihipoksički u uvjetima krvne i cirkulacijske hipoksije u mozgu

Synthesis and antiprotozoal activity of oligomethylene- and p-phenylene-bis(methylene)-linked bis(+)-huprines.

We have synthesized a series of dimers of (+)-(7R,11R)-huprine Y and evaluated their activity against Trypanosoma brucei, Plasmodium falciparum, rat myoblast L6 cells and human acetylcholinesterase (hAChE), and their brain permeability. Most dimers have more potent and selective trypanocidal activity than huprine Y and are brain permeable, but they are devoid of antimalarial activity and remain active against hAChE. Lead optimization will focus on identifying compounds with a more favourable trypanocidal/anticholinesterase activity ratio

Laser-induced control of the optical response of aluminum phthalocyanine chloride complexes dissolved in ethanol

We show that absorption spectra of aluminum chloride phthalocyanine (AlClPc) in the liquid phase can be dynamically modified through the time-resolved interaction with a second laser pulse during a time window on the order of 100 fs. The observed effects can be explained by laser-induced coherent coupling dynamics between the ground state and a bath of excited states as reproduced by a few-level toy model. The presented results help to understand how intense laser fields interact with complex molecules in solution, but in their laser-controlled response still much alike isolated atoms in the gas phase. This understanding can, in the future, be used to modify and control the dynamics in complex systems

Signifikante Unterschiede in der schriftlichen Wissenskontrolle durch ein Blended-Learning-Konzept im Rahmen eines internistischen Untersuchungskurses: eine randomisiert-kontrollierte Pilotstudie

Background: Taking a medical history and performing a physical examination represent basic medical skills. However, numerous national and international studies show that medical students and physicians-to-be demonstrate substantial deficiencies in the proper examination of individual organ systems.Aim: The objective of this study was to conduct a randomized controlled pilot study to see if, in the context of a bedside clinical examination course in internal medicine, an additional app-based blended-learning strategy resulted in (a) higher satisfaction, better self-assessments by students when rating their history-taking skills (b1) and their ability to perform physical examinations (b2), as well as (c) higher multiple-choice test scores at the end of the course, when compared to a traditional teaching strategy.Methods: Within the scope of a bedside course teaching the techniques of clinical examination, 26 students out of a total of 335 students enrolled in the 2012 summer semester and 2012/2013 winter semester were randomly assigned to two groups of the same size. Thirteen students were in an intervention group (IG) with pre- and post-material for studying via an app-based blended-learning tool, and another 13 students were in a control group (CG) with the usual pre- and post-material (handouts). The IG was given an app specifically created for the history-taking and physical exam course, an application program for smartphones enabling them to view course material directly on the smartphone. The CG received the same information in the form of paper-based notes. Prior to course begin, all of the students filled out a questionnaire on sociodemographic data and took a multiple-choice pretest with questions on anamnesis and physical examination. After completing the course, the students again took a multiple-choice test with questions on anamnesis and physical examination.Results: When compared to the CG, the IG showed significantly more improvement on the multiple-choice tests after taking the clinical examination course (p=0.022). This improvement on the MC tests in the IG significantly correlated with the amount of time spent using the app (Spearman's rho=0.741, p=0.004).Conclusion: When compared to conventional teaching, an app-based blended-learning approach leads to improvement in test scores, possibly as a result of more intensive preparation for and review of the clinical examination course material.Hintergrund: Die Erhebung der Anamnese und die Durchführung körperlicher Untersuchungstechniken stellen eine grundlegende Kompetenz des ärztlichen Handelns dar. Allerdings zeigen zahlreiche nationale und internationale Studien, dass bei Medizinstudierenden und angehenden Ärzten erhebliche Defizite in der korrekten Durchführung der körperlichen Untersuchung einzelner Organsysteme vorliegen.Zielsetzung: Ziel der vorliegenden Studie war es, in einer randomisiert-kontrollierten Pilotstudie zu überprüfen, ob im Rahmen eines internistischen Bedside-Teaching ein zusätzliches App-basiertes Blended-Learning-Konzept im Vergleich zum klassischen Lehrkonzept (a) zu einer höheren Zufriedenheit, zu einer besseren Selbsteinschätzung der Studierenden bezüglich der Anamneseerhebung (b1) und der Durchführung der körperlichen Untersuchung (b2), als auch (c) zu besseren Multiple-Choice (MC)-Prüfungsergebnissen am Ende des Kurses führt.Methodik: Im Rahmen des internistischen Untersuchungskurses / Bedside-Teaching wurden von insgesamt 335 Studierenden des Sommersemesters 2012 und des Wintersemesters 2012/2013 26 Studierende randomisiert zwei gleich großen Gruppen zugewiesen: 13 Studierende einer Interventionsgruppe (IG) mit Vor- und Nachbereitungsmaterial anhand eines App-basierten Blended-Learning-Konzepts und 13 Studierende einer Kontrollgruppe (KG) mit konventionellem Vor- und Nachbereitungsmaterial (Handout). Die IG erhielt eine auf den Anamnese- und Untersuchungskurs zugeschnitte App, ein Anwendungsprogramm für Smartphones, das es ermöglicht, Lehrmaterial für den Untersuchungskurs direkt auf dem Smartphone einzusehen. Die KG erhielt dieselben Informationen anhand von Skripten. Vor Beginn des Untersuchungskurses füllten alle Studierenden Fragebögen zu soziodemographischen Daten aus und nahmen an einer Eingangs-MC-Klausur mit MC-Fragen zur Anamnese und körperlicher Untersuchung teil. Nach Abschluss des Untersuchungskurses nahmen die Studierenden erneut an einer MC-Klausur mit MC-Fragen zu Anamnese und körperlicher Untersuchung teil.Ergebnisse: Die IG zeigte im Vergleich zur KG eine signifikant höhere Verbesserung in den MC-Klausuren nach Durchlaufen des Untersuchungskurses (p=0,022). Die Verbesserung in den MC-Klausuren korrelierte in der IG signifikant mit der zeitlichen Beschäftigung mit der App (Spearmans rho=0.741, p=0.004). Schlussfolgerung: Ein App-basiertes Blended-Learning-Konzept führt im Vergleich zum klassischen Lehrkonzept, möglicherweise durch einer intensivere Vor- und Nachbereitung des klinischen Untersuchungskurses, zu einer Verbesserung in den Prüfungsergebnissen

Role of interfaces on the stability and electrical properties of Ge2Sb2Te5 crystalline structures

GeSbTe-based materials exhibit multiple crystalline phases, from disordered rocksalt, to rocksalt with ordered vacancy layers, and to the stable trigonal phase. In this paper we investigate the role of the interfaces on the structural and electrical properties of Ge2Sb2Te5. We find that the site of nucleation of the metastable rocksalt phase is crucial in determining the evolution towards vacancy ordering and the stable phase. By properly choosing the substrate and the capping layers, nucleation sites engineering can be obtained, thus promoting or preventing the vacancy ordering in the rocksalt structure or the conversion into the trigonal phase. The vacancy ordering occurs at lower annealing temperatures (170 °C) for films deposited in the amorphous phase on silicon (111), compared to the case of SiO2 substrate (200°C), or in presence of a capping layer (330°C). The mechanisms governing the nucleation have been explained in terms of interfacial energies. Resistance variations of about one order of magnitude have been measured upon transition from the disordered to the ordered rocksalt structure and then to the trigonal phase. The possibility to control the formation of the crystalline phases characterized by marked resistivity contrast is of fundamental relevance for the development of multilevel phase change data storage

Predicting the need of aortic valve surgery in patients with chronic aortic regurgitation: a comparison between cardiovascular magnetic resonance imaging and transthoracic echocardiography

Abstract To compare the ability of cardiac magnetic resonance tomography (CMR) and transthoracic echocardiography (TTE) to predict the need for valve surgery in patients with chronic aortic regurgitation on a mid-term basis. 66 individuals underwent assessment of aortic regurgitation (AR) both in CMR and TTE between August 2012 and April 2017. The follow-up rate was 76% with a median of 5.1 years. Cox proportional hazards method was used to assess the association of the time-to-aortic-valve-surgery, including valve replacement and reconstruction, and imaging parameters. A direct comparison of most predictive CMR and echocardiographic parameters was performed by using nested-factor-models. Sixteen patients (32%) were treated with aortic valve surgery during follow-up. Aortic valve insufficiency parameters, both of echocardiography and CMR, showed good discriminative and predictive power regarding the need of valve surgery. Within all examined parameters AR gradation derived by CMR correlated best with outcome [χ2 = 27.1; HR 12.2 (95% CI: 4.56, 36.8); (p < 0.0001)]. In direct comparison of both modalities, CMR assessment provided additive prognostic power beyond echocardiographic assessment of AR but not vice versa (improvement of χ2 from 21.4 to 28.4; p = 0.008). Nested model analysis demonstrated an overall better correlation with outcome by using both modalities compared with using echo alone with the best improvement in the moderate to severe AR range with an echo grade II out of III and a regurgitation fraction of 32% in CMR. This study corroborates the capability of CMR in direct quantification of AR and its role for guiding further treatment decisions particularly in patients with moderate AR in echocardiography