Near-equilibrium measurement of quantum size effects using Kelvin probe force microscopy

In nano-structures such as thin films electron confinement results in the quantization of energy levels in the direction perpendicular to the film. The discretization of the energy levels leads to the oscillatory dependence of many properties on the film thickness due to quantum size effects. Pb on Si(111) is a specially interesting system because a particular relationship between the Pb atomic layer thickness and its Fermi wavelength leads to a periodicity of the oscillation of two atomic layers. Here, we demonstrate how the combination of scanning force microscopy (SFM) and Kelvin probe force microscopy (KPFM) provides a reliable method to monitor the quantum oscillations in the work function of Pb ultra-thin film nano-structures on Si(111). Unlike other techniques, with SFM/KPFM we directly address single Pb islands, determine their height while suppressing the influence of electrostatic forces, and, in addition, simultaneously evaluate their local work function by measurements close to equilibrium, without current-dependent and non-equilibrium effects. Our results evidence even-odd oscillations in the work function as a function of the film thickness that decay linearly with the film thickness, proving that this method provides direct and precise information on the quantum states.Comment: This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Nanoscale, copyright Royal Society of Chemistry after peer review. To access the final edited and published work see doi belo

Atomically resolved scanning force studies of vicinal Si(111)

Well-ordered stepped semiconductor surfaces attract intense attention owing to the regular arrangements of their atomic steps that makes them perfect templates for the growth of one- dimensional systems, e.g. nanowires. Here, we report on the atomic structure of the vicinal Si(111) surface with 10 degree miscut investigated by a joint frequency-modulation scanning force microscopy (FM-SFM) and ab initio approach. This popular stepped surface contains 7 x 7-reconstructed terraces oriented along the Si(111) direction, separated by a stepped region. Recently, the atomic structure of this triple step based on scanning tunneling microscopy (STM) images has been subject of debate. Unlike STM, SFM atomic resolution capability arises from chemical bonding of the tip apex with the surface atoms. Thus, for surfaces with a corrugated density of states such as semiconductors, SFM provides complementary information to STM and partially removes the dependency of the topography on the electronic structure. Our FM-SFM images with unprecedented spatial resolution on steps confirm the model based on a (7 7 10) orientation of the surface and reveal structural details of this surface. Two different FM-SFM contrasts together with density functional theory calculations explain the presence of defects, buckling and filling asymmetries on the surface. Our results evidence the important role of charge transfers between adatoms, restatoms, and dimers in the stabilisation of the structure of the vicinal surface

Spektroskopische Untersuchungen an Supraleitern mittels Punktkontaktspektroskopie und Rastertunnelmikroskopie

In der Arbeit wird der Aufbau eines RTM, das bei tiefen Temperaturen und großen magnetischen Feldern $B>10\,$T funktionstüchtig ist, beschrieben. Untersucht wurden die Schwerfermionensupraleiter CeCoIn$_5$ und Sr$_2$RuO$_4$. Ein weiterer Teil der Arbeit beschäftigt sich mit Punktkontaktspektroskopie an den Eisenpnictidsupraleiter Ba$_{1-x}$K$_x$Fe$_2$As$_2$ und Ba(Fe,Co)$_2$As$_2$

Real-space imaging of several molecular layers of C60_{60} in the rotational glass phase

C$_{60}$ is a model system to study molecule–surface interactions and phase transitions due to its high symmetry and strong covalent π bonding within the molecule versus weak van-der-Waals coupling between neighboring molecules. In the solid, at room temperature, the molecule rotates and behaves as a sphere. However, the pentagonal and hexagonal atomic arrangement imposes deviations from the spherical symmetry that become important at low temperatures. The orientation of the C$_{60}$ can be viewed to represent classic spins. For geometrical reasons the preferred orientation of neighboring C$_{60}$ cannot be satisfied for all of the neighboring molecules, making C$_{60}$ a model for disordered spin systems with frustration. We study several molecular layers of C$_{60}$ islands on highly oriented pyrolytic graphite using scanning tunneling microscopy at liquid nitrogen temperatures. By imaging several layers we obtain a limited access to the three-dimensional rotational structure of the molecules in an island. We find one rotationally disordered layer between two partially rotationally ordered layers with hexagonal patterns. This exotic pattern shows an example of the local distribution of order and disorder in geometrically frustrated systems. Scanning tunneling spectroscopy data confirms the weak interactions of neighboring molecules

Real-space imaging of several molecular layers of C60 in the rotational glass phase

C60 is a model system to study molecule–surface interactions and phase transitions due to its high symmetry and strong covalent π bonding within the molecule versus weak van-der-Waals coupling between neighboring molecules. In the solid, at room temperature, the molecule rotates and behaves as a sphere. However, the pentagonal and hexagonal atomic arrangement imposes deviations from the spherical symmetry that become important at low temperatures. The orientation of the C60 can be viewed to represent classic spins. For geometrical reasons the preferred orientation of neighboring C60 cannot be satisfied for all of the neighboring molecules, making C60 a model for disordered spin systems with frustration. We study several molecular layers of C60 islands on highly oriented pyrolytic graphite using scanning tunneling microscopy at liquid nitrogen temperatures. By imaging several layers we obtain a limited access to the three-dimensional rotational structure of the molecules in an island. We find one rotationally disordered layer between two partially rotationally ordered layers with hexagonal patterns. This exotic pattern shows an example of the local distribution of order and disorder in geometrically frustrated systems. Scanning tunneling spectroscopy data confirms the weak interactions of neighboring molecules

Tuning research competences for Bologna three cycles in medicine:report of a MEDINE2 European consensus survey

Medical curricula, like healthcare systems and medical practice, have a strong cultural component and vary considerably between countries. Increasing mobility of medical graduates, and increasing pressure to ensure they are all fit for practice, have highlighted an urgent need to establish common ground in learning outcomes at all stages of training. A research-based approach, developed by the Tuning project, was used previously by the MEDINE Thematic Network to gain consensus on core learning outcomes/competences for primary medical degrees (www.tuning-medicine.com), but no consensus was reached for learning outcomes relating to research. As part of MEDINE2, a focussed Tuning project was undertaken to explore opinions on more detailed core learning outcomes in research for all three Bologna cycles (Bachelor, Master, and Doctor). Responses from 417 stakeholders, representing 29 European and 13 non-European countries, revealed a relatively high degree of consensus. The findings strongly suggest that these stakeholders think that learning outcomes related both to ‘using research’ and ‘doing research’ should be core components of medical curricula in Europe. The challenge now, however, is to promote further local and international discussion on these issues, and to find ways of achieving these competences within the context of already crowded medical curricula

Low field extension for magnetometers (TinyBee) used for investigations on low-dimensional superconductors with Bc1 < 5G

In this article a simple and easy to install low magnetic field extension of the SQUID magnetometer Quantum Design MPMS-7 is described. This has been accomplished by complementing the MPMS-7 magnet control system with a laboratory current supply for the low magnetic field region (B \leq 200G). This hard- and software upgrade provides a significant gain in the magnetic field accuracy up to an order of magnitude compared with the standard instrument's setup and is improving the resolution to better than 0.01G below 40G. The field control has been integrated into the Quantum Design MultiVu software for a transparent and user-friendly operation of this extension. The improvements achieved are especially useful, when low magnetic field strengths (B < 1G) are required at high precision. The specific advantages of this application are illustrated by sophisticated magnetic characterisation of lowdimensional superconductors like Sc3CoC4 and SnSe2{Co({\eta}-C5H5)2}x.Comment: 16 pages, 7 figure

Research program of the research unit "Cultural Sources of Newness"

"In this discussion paper the program of the Research Unit 'Cultural Sources of Newness' is presented. Short descriptions of currently nine projects follow. The assumption driving the research program is that newness lies at the core of innovations and emerges in cultural sources, which are analyzed as cultural configurations. The research focuses on the relevance of these cultural constellations rather than on technical or political aspects. Three kinds of processes are identified as being decisive for innovations: 1) the continuous variation of cultural forms and practices; 2) the evaluation of newness; 3) the states of tension that arise within and between cultures. The research program assumes that the interplay of these three processes determines the spectrum and spread of successful innovations. The program is organized in three empirical strands. The strands cover the spatial, interactive and temporal dimensions of cultural configurations, and the projects focus on phenomena of different orders of magnitude." (author's abstract)"Im ersten Teil wird das Forschungsprogramm der Abteilung 'Kulturelle Quellen von Neuheit' entwickelt, im zweiten Teil folgen kurze Beschreibungen von insgesamt neun Projekten. Neuheit, so die zugrundeliegende Annahme des Forschungsprogramms, bildet den Kern von Innovationen und entsteht aus kulturellen Quellen, die als kulturelle Konfigurationen analysiert werden. Die Relevanz dieser kulturellen Konstellationen für das Innovationsgeschehen - im Unterschied zu technischen oder politischen Aspekten - ist der Gegenstand der Forschung. Dabei gelten drei Prozesse als entscheidend für die Qualität und Anschlussfähigkeit von Innovationen: 1) die ständige Variation kultureller Selbstverständlichkeiten, 2) Prozesse der Bewertung als Neuheit und 3) Spannungszustände, die in und zwischen Kulturen auftreten. Das Zusammenspiel dieser drei Prozesse, so die These, bestimmt das Spektrum und die Reichweite der Innovationen. Die empirischen Felder des Forschungsprogramms sind aus der räumlichen, interaktiven und zeitlichen Dimensionierung kultureller Konfigurationen hergeleitet. In jedem der Felder untersuchen die Projekte Phänomene unterschiedlicher Größenordnung." (Autorenreferat

APOE polymorphism and its effect on plasma C-reactive protein levels in a large general population sample

The literature on association between apolipoprotein E (APOE) gene variations and plasma levels of C-reactive protein (CRP) remains inconsistent, mainly due to low statistical power of previous studies. To clarify this question, we analysed data from large population sample of randomly selected individuals from 7 Czech towns (2886 males and 3344 females, the HAPIEE study). In both males and females, the lowest levels of plasma hsCRP were observed in the carriers of the APOE ε4ε4 and ε4ε3 genotypes. The median (inter-quartile range, IQR) concentration of hsCRP in carriers of the most common APOE ε3ε3 genotype (two thirds of participants) was 1.13 (IQR 0.56; 2.33) mg/l in men and 1.23 (IQR 0.61; 2.65) mg/l in women, compared with 0.72 (IQR 0.61; 0.86) mg/l in male and 0.72 (IQR 0.61-0.85) mg/l in female carriers of APOE ε4ε3/ε4ε4 genotypes; the differences were statistically significant (p<0.001). The association between APOE and CRP was not materially affected by adjustment for age, sex, history of cardiovascular disease or cardiovascular risk factors. This study, the largest to date, provides robust evidence of an association between plasma hsCRP and the APOE genotype, an association not explained by history of cardiovascular disease nor its risk factors

Cellular gene expression during Hepatitis C virus replication as revealed by Ribosome Profiling

Background: Hepatitis C virus (HCV) infects human liver hepatocytes, often leading to liver cirrhosis and hepatocellular carcinoma (HCC). It is believed that chronic infection alters host gene expression and favors HCC development. In particular, HCV replication in Endoplasmic Reticulum (ER) derived membranes induces chronic ER stress. How HCV replication affects host mRNA translation and transcription at a genome wide level is not yet known. Methods: We used Riboseq (Ribosome Profiling) to analyze transcriptome and translatome changes in the Huh-7.5 hepatocarcinoma cell line replicating HCV for 6 days. Results: Established viral replication does not cause global changes in host gene expression—only around 30 genes are significantly differentially expressed. Upregulated genes are related to ER stress and HCV replication, and several regulated genes are known to be involved in HCC development. Some mRNAs (PPP1R15A/GADD34, DDIT3/CHOP, and TRIB3) may be subject to upstream open reading frame (uORF) mediated translation control. Transcriptional downregulation mainly affects mitochondrial respiratory chain complex core subunit genes. Conclusion: After establishing HCV replication, the lack of global changes in cellular gene expression indicates an adaptation to chronic infection, while the downregulation of mitochondrial respiratory chain genes indicates how a virus may further contribute to cancer cell-like metabolic reprogramming (“Warburg effect”) even in the hepatocellular carcinoma cells used here