1,255 research outputs found
The people behind the papers – Dennis de Bakker, Mara Bouwman and Jeroen Bakkers
No full textUnlike mammals, adult zebrafish are capable of regenerating their hearts without scarring after injury – a process that has great therapeutic potential. A new paper in Development investigates the role of Prxx1b, a transcription factor that is expressed in epicardial heart tissue after injury, to understand its role in the scar-free regeneration of the adult zebrafish heart. To hear more about the study, we caught up with joint first authors, Dennis De Bakker and Mara Bouwman, and the corresponding author, Jeroen Bakkers, the group leader at the Hubrecht Institute and professor of Molecular Cardiogenetics at the University Medical Center in Utrecht, The Netherlands
Surveys of flying bird nesting areas and adelie penguin colonies in the Windmill Islands 1998/99 by Jonny Stark and Jeroen Creuwels
No full textProgress Code: completedStatement: The locations of some colonies on Nelly Island (Frazier Islands), a South Polar Skua nest site on Dewart Island (Frazier Islands) and some South Polar Skua nest sites on Ardery Island were eyed in using as a guide field survey sketches by Jeroen Creuwels in June 1999. The locations of some further colonies on the Frazier Islands, a Southern Giant-petrel nest site on Dewart Island (Frazier Islands) and some Snow Petrel nest sites at Casey Station were sourced from a differentially corrected GPS survey by Jonny Stark of the Australian Antarctic Division in 1998/99. The following data relevant to Jeroen Creuwels' 1998/99 work on Ardery Island were sourced from another differentially corrected GPS survey by Jonny Stark in 1998/99: Antarctic Petrel reference area, Southern Fulmar reference area, Cape Petrel study area, Cape Petrel reference area and the location of the observation point for the 1998/99 bird census.
Each feature has a Qinfo value which can be used to access data quality information (see provided URL).This GIS dataset contains bird data from 1998/99 field work in the Windmill Islands by Jonny Stark and Jeroen Creuwels. The locations are Frazier Islands, Ardery Island and Casey station. <br/>Polygon data represents the extents of flying bird nesting areas and adelie penguin colonies.<br/>Point data represents flying bird nest locations
Low-temperature resistivity and Hall effect measurements of the Kondo insulator CeRu4Sn6
No full textLow-temperature resistivity and Hall effect measurements
of the Kondo insulator CeRu4Sn6
Poster
1st International Workshop:
The New Generation in Strongly Correlated Electron Systems
By: Karl-Anton Lorenzer
From: Vienna University of Technology
When: 20.-26.06.2010, Lanzarote, Spain
Authors: K.-A. Lorenzer, H. Winkler, J. Custers, A. Prokofiev, and S. Paschen
Abstract: Recently, specific heat and magnetization measurements on single
crystalline CeRu4Sn6 revealed pronounced anisotropies [1], suggesting
that this compound may be a nodal Kondo insulator. Amazingly, strong
anisotropy was not only found along the fundamental crystal directions
(tetragonal a- and c-direction) but also within a quasi cubic cell arising in
this compound due to the lattice parameter in the [0 0 1] direction (c)
almost matching the lattice spacing in the [1 1 0] direction (c'). Here, we
present and discuss results of electrical resistivity measurements on
single crystalline CeRu4Sn6 samples down to 25 mK for different
magnetic fields up to 15 T aligned parallel to the tetragonal a- and cdirection
and to the quasi-cubic c'-direction.
[1] S. Paschen, H. Winkler, T. Nezu, M. Kriegisch, G. Hilscher, J. Custers,
and A. Prokofiev 2010 J. Phys.: Conf. Ser. (to be published)
We acknowledge financial support from the European Research
Council/ERC Advanced Grant No. 227378 and from the Austrian Science
Fund/FWF project P19458-N16
Correction to: The ‘can do, do do’ concept in COPD; quadrant interpretation, affiliation and tracking longitudinal changes
No full textFollowing publication of the original article [1], the authors identified a mistake in the author names, as both forename and initials were stated. Initially published author names: A. J. Alex van ’t Hul, E. H. Noortje Koolen, H. W. Jeroen van Hees, B. Bram van den Borst and M. A. Martijn Spruit Correct author names: Alex J. van ‘t Hul, Noortje H. Koolen, Jeroen W. van Hees, Bram van den Borst, Martijn A. Spruit. The original article has been corrected.</p
Torque magnetometry on intermetallic Cerium compounds and construction of a Faraday magnetometer
No full textMit Drehmoment-Magnetometrie kann die magnetische Anisotropie von Materialien sehr genau bestimmt werden. In dieser Arbeit wurden Drehmoment-Messungen zur Bestimmung der magnetokristallinen Anisotropie an CeRu4Sn6 und CeAuGe durchgeführt. CeRu4Sn6 gehört zur Klasse der Käfigverbindungen und ist damit ein vielversprechender Kandidat für thermoelektrische Anwendungen. Es kann als Kondo-Isolator klassifiziert werden, das genaue Verhalten der Energielücke ist jedoch noch nicht geklärt. Das Studium an dieser Verbindung ist insbesondere interessant, da die tetragonale Kristallstruktur durch eine quasikubische Einheitszelle angenähert werden kann.Magnetokristalline Anisotropie wurde sowohl in der tetragonalen als auch in der kubischen Struktur gemessen. Die vergleichsweise große Magnetisierung in die a- sowie die c'-Achse im Vergleich zur c-Richtung konnte bestätigt werden. Die Berechnung des Absolutwerts der Magnetisierung in der harten c-Richtung ergibt einen deutlich kleineren Wert als bisherige direkte Magnetisierungs-Messungen gezeigt haben. CeAuGe ist ein seltenes Beispiel für eine ferromagnetisch ordnende Cer-Verbindung mit einer Curie-Temperatur von etwa 10 Kelvin. Die hexagonale Kristallstruktur besteht aus einer ABAC-Stapelfolge mit, aufgrund des vergleichsweise großen Interlagenabstandes, geringen Bindung zwischen den Lagen. Drehmoment-Messungen zeigen eine große Anisotropie sowohl zwischen der c- und der a-Achse als auch zwischen der c-Richtung und der Diagonalen der a-a-Ebene, hier mit a' bezeichnet.Dies deutet auf eine Orientierung der magnetischen Momente in der a-a-Ebene hin.Der Wert der Anisotropie ist etwas geringer als der aus direkten Magnetisierungsmessungen bestimmte. Der zweite Teil dieser Arbeit bestand aus der Konstruktion eines Faradaykraft-Magnetometers.Dieses soll vor allem bei sehr tiefen Temperaturen und hohen magnetischen Feldern zum Einsatz kommen. In diesem Bereich kann ein SQUID-Magnetometer nicht eingesetzt werden und ein Foner-Magnetometer führt, aufgrund von Reibung, zu sehr großen Aufwärmeffekten.Das Magnetometer wurde erfolgreich konstruiert, zusammengebaut und getestet. Erste Messungen zeigen einen hohen Wert der Kapazität von C =13.3 pF bei guter Isolierung. Auch die Langzeitstabilität der Zelle scheint ausreichend.Test-Messungen durch Gewichtsbelastungen der Probenplattform der Zelle zeigen eine, im Vergleich zu anderen Zellen diesen Typs, hohe Sensitivität und ein annähernd lineares Verhalten.Torque magnetometry is a very sensitive tool to probe the magnetic anisotropy of materials. Two intermetallic Cerium compounds were investigated with this technique.CeRu4Sn6 is a cage compound and a promising candidate for thermoelectric applications. It is classified as a Kondo insulator. The crystal structure is tetragonal but can be approximated by a cubic unit cell, with c and c', the diagonal of the a-a-plane, as axes.Magnetocrystalline anisotropy was observed both in the tetragonal and in the quasi-cubic cell. The a- and c'-axis were confirmed as easy axes, the c-axis is the hard axis. The value of the magnetization in the c-direction was calculated. It is lower than the value determined previously from magnetic susceptibility measurements, where any small sample missalignement leads to too large values. CeAuGe is a rare example of a ferromagnetic Cerium compound with a Curie temperature of about 10 Kelvin. It has a hexagonal crystal structure with an ABAC stacking order and only weak interaction between subsequent layers. The orientation of the magnetic moments within the a-a-plane was confirmed by a strong anisotropy between the c- and the a-direction as well as between the c-direction and the diagonal of the a-a-plane, a'.This points to a random orientation of the magnetic moments within the a-a-plane. The value of the anisotropy is slightly lower than expected from preliminary SQUID-measurements. In the second part of this thesis a Faraday force magnetometer was constructed. It can be used to measure magnetization at very low temperatures and high fields. There it surpasses a vibrating sample magnetometer in performance and it can be used at higher fields than possible in a SQUID magnetometer.First measurements show a large capacity of around C =13.3 pF, a good isolation of the magnetometer and good longtime stability of the signal.First tests show, that the sensitivity is larger than in other magnetometers using this technique and the response is linear in a wide range of applied forces
Resistivity and hall effect measurements on clathrates and clathrate-like compounds
No full textThe search for materials with thermoelectric application has led to the analysis of complex intermetallic alloys. The quality of a thermoelectric material is given by the dimensionless figure of merit ZT = S2T/rk. In this work, data on the resistivity of the poly- crystalline clathrates Ba8NixGe46-x-y□y and the single crystalline complex metallic alloy Ce3Pd20Si6, as well as the Hall constant of Ce3Pd20Si6,is presented in the temperature range 300 K to 4 K and in magnetic fields up to 9 T. The resistivity of Ba8NixGe46-x-y□y becomes larger with Ni-doping and the behaviour ranges from metallic to semiconductor-like.The results on Ce3Pd20Si6 are compared to published data and the effects of crystallity and purity on the properties of this compound are discussed
Thermoelectric properties of complex metallic alloys
No full textIn der vorliegenden Diplomarbeit wurden die thermoelektrischen Eigenschaften verschiedener polykristalliner Typ-I-Clathrate untersucht.Diese Arbeit war Teil eines Projekts des FP6 NoE Complex Metallic Alloys (CMA). Alle Clathrate wurden am Max-Planck-Institut für Chemische Physik fester Stoffe in Dresden hergestellt, im Rahmen dieser Arbeit bezüglich der thermoelektrischen Eigenschaften charakterisiert und am CMTR-ICMPE in Thiais in einen Testgenerator eingebaut.Die Proben lassen sich in vier Gruppen einteilen: zwei Probengruppen des BaGaGe-Systems, welche sich durch das verwendete Herstellungsverfahren unterscheiden, sowie Proben des EuGaGe- und des BaNiGe-Systems.Es wurden der spezifische elektrische Widerstand und der Seebeckkoeffizient zwischen 4 und 575 K und die thermische Leitfähigkeit zwischen 4.5 und 480 K bestimmt. Daraus wurde die dimensionslose thermoelektrische Leistungskennzahl ZT berechnet, die ein Maß für die thermoelektrische Leistungsfähigkeit eines Materials darstellt.Mit Ausnahme einer Probe des BaNiGe-Systems waren alle Materialien n-Typ-Leiter. Aus den Messergebnissen konnten Informationen über den Einfluss der nominellen Zusammensetzung und des Herstellungsverfahrens auf die tatsächliche Zusammensetzung, die Mikrostruktur und die physikalischen Eigenschaften der Clathrate gewonnen werden. Im Speziellen konnte eine systematische Änderung der physikalischen Eigenschaften mit variierendem Nickelgehalt festgestellt werden.Die mechanisch stabilsten Clathrate wurden jeweils mit einem p-Typ-Skutterudit in einen Testgenerator eingebaut. Die mit Hilfe des Generators gemessenen Leistungsdichten wurden berechneten Leistungsdichten gegenübergestellt, die aus den Messergebnissen dieser Arbeit ermittelt wurden.In the presented diploma thesis the thermoelectric properties of different polycrystalline type-I clathrates were investigated within the FP6 NoE Complex Metallic Alloys (CMA). All materials were synthesized at the Max Planck Institute for Chemical Physics of Solids in Dresden, investigated for their thermoelectric performance at TU Vienna (this work) and used in a thermoelectric demonstrator at CMTR-ICMPE in Thiais.The investigated samples can be classified into four groups. Two groups consist of samples of the BaGaGe-system prepared by two different methods, the others are samples of the BaNiGe- and the EuGaGe-system.The electrical resistivity and Seebeck coefficient of these samples were measured in the temperature range of 4 to 575 K, the thermal conductivity was determined between 4.5 and 480 K. These properties enter the expression for the dimesionless thermoelectric figure-of-merit ZT, which characterizes a material's efficiency concerning thermoelectric power generation or cooling.Except for one sample of the BaNiGe-system, all investigated clathrates were n-type materials. The influence of the starting composition and of different preparation methods on the material's final composition, microstructure, and physical properties was derived. In particular, a systematic evolution of the physical properties of BaNiGe-clathrates with varying Ni-content was observed. The mechanically most stable samples were included in a generator in combination with a p-type skutterudite. The resulting experimental power densities were compared to power densities that were calculated on the basis of the measured data from this work
Aufbau eines Probenstabs zur hochgenauen Messung des Hall-Effekts an YbIr2Si2
No full textWenn ein Schweres-Fermionen-System bei T = 0 einen Phasenübergang zweiter Ordnung durchläuft, tritt ein quantenkritischer Punkt auf. Für T > 0 findet man im Allgemeinen Nicht-Fermi-Flüssigkeitsverhalten, das sich zum Beispiel im elektrischen Widerstand manifestiert. Das Schwere-Fermionen- System YbRh2Si2 weist einen durch ein äußeres Magnetfeld induzierten quantenkritischen Punkt auf. Bei dieser Verbindung wurde eine Anomalie im Hall-Koeffizienten gefunden, die ihren Ursprung im quantenkritischen Punkt hat. Das isostrukturelle Schwere-Fermionen-System YbIr2Si2 zeigt keine magnetische Ordnung bis T = 20 mK. Die Motivation, YbIr2Si2 zu untersuchen, besteht in der Vermutung, dass sich YbIr2Si2 im Phasendiagramm auf der paramagnetischen Seite eines quantenkritischen Punktes befindet.Dies wurde durch Messungen des Hall-Effekts und des elektrischen Widerstands untersucht. Die in Analogie zu YbRh2Si2 erwarteten Anomalien im Hall-Koeffizienten konnten nicht eindeutig nachgewiesen werden. Die starke Magnetfeldabhängigkeit des Hall-Koeffizienten wird im Rahmen eines Zwei- Band-Modells diskutiert. Der Temperaturverlauf des Hall-Koeffizienten ist aber ein erstes Anzeichen für eine solche Analogie.When a heavy fermion system undergoes a second order phase transistion at T = 0, a quantum critical point is found. Non-Fermi-Liquid-behaviour is usually found for T > 0, which becomes for example evident in the electrical resistivity. The heavy fermion compound YbRh2Si2 shows a magnetic field induced quantum critical point. An anomaly in the Hall-coefficient which originates from the quantum critical point was found. The isostructural heavy fermion system YbIr2Si2 shows no magnetic ordering down to T = 20 mK.The motivation to study YbIr2Si2 is prompted by the speculation that this system is on the paramagnetic side of a quantum critical point. For this reason measurements on the Hall-effect and on electrical resistivity were conducted to confirm this assumption. The expected anomalous behaviour in the Hall- coefficient like in YbRh2Si2 could not be detected unambiguously. The strong magnetic field dependency is interpreted within a Two-Band-Model.However, the temperature dependent Hall-coefficient is a first indication of such an analogy
The Quest for Citations: Drivers of Article Impact
No full textWhy do some articles become building blocks for future scholars, while many others remain unnoticed? We aim to answer this question by contrasting, synthesizing and simultaneously testing three scientometric perspectives – universalism, social constructivism and presentation – on the influence of article and author characteristics on article citations. To do so, we study all articles published in a sample of five major journals in marketing from 1990 to 2002 that are central to the discipline. We count the number of citations each of these articles has received and regress this count on an extensive set of characteristics of the article (i.e. article quality, article domain, title length, the use of attention grabbers and expositional clarity), and the author (i.e. author visibility and author personal promotion). We find that the number of citations an article in the marketing discipline receives, depends upon “what one says†(quality and domain), on “who says it†(author visibility and personal promotion) and not so much on “how one says it†(title length, the use of attention grabbers, and expositional clarity). Our insights contribute to the marketing literature and are relevant to scientific stakeholders, such as the management of scientific journals and individual academic scholars, as they strive to maximize citations. They are also relevant to marketing practitioners. They inform practitioners on characteristics of the academic journals in marketing and their relevance to decisions they face. On the other hand, they also raise challenges towards making our journals accessible and relevant to marketing practitioners: (1) authors visible to academics are not necessarily visible to practitioners; (2) the readability of an article may hurt academic credibility and impact, while it may be instrumental in influencing practitioners; (3) it remains questionable whether articles that academics assess to be of high quality are also managerially relevant.Impact;Citation Analysis;Referencing;Scientometrics;Cite
Hildegard de Bingen y su libro "Scivias". Ideología y conocimientos de una religiosa del siglo XII
No full textEl trabajo de Jeroen Deploige es un estudio de las fuentes bíblicas en la obra Scivias ("Conoce las vías [del Señor]") de la religiosa Hildegard de Bingen (1098-1179). En esta, su obra visionaria más conocida, así como en sus cartas y fragmentos autobiográficos, Hildegard se presenta como mujer ignorante, instruida no por los libros, sino solo por la Ciencia Divina, que la instruye en la interioridad de su alma y le hace ver y escuchar lo que ella escribe en sus obras. En su artículo, Deploige (autor de un libro recientemente publicado sobre Hildegard) muestra que al menos las lecturas bíblicas de esta escritora no se diferenciaban de las de los grandes autores masculinos de su siglo.
Jeroen Deploige's work is a study of bíblical sources in "Scivias" (Know thee the ways [of the Lord] by the religious writer Hildegard de Bingen (1098-1179). In this, her best known visionary work, as in her letters and autobiographical fragments, Hildegard presents herself as an ignorant woman, instructed not by books, but by Divine Science, which instructs her in her innermost self, and permits her to see and hear that which she writes down in her works. In his article, Deploige (author of a recently published book on Hildegard) shows that at the least, the biblical readings of this writer did not differ from those of the great masculine writers of her century
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