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Search Results: 1 - 10 of 499 matches for " Frederik Edler "
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Local transport measurements on epitaxial graphene
Jens Baringhaus,Frederik Edler,Christoph Neumann,Christoph Stampfer,Stiven Forti,Ulrich Starke,Christoph Tegenkamp
Physics , 2013, DOI: 10.1063/1.4821364
Abstract: Growth of large-scale graphene is still accompanied by imperfections. By means of a four-tip STM/SEM the local structure of graphene grown on SiC(0001) was correlated with scanning electron microscope images and spatially resolved transport measurements. The systematic variation of probe spacings and substrate temperature has clearly revealed two-dimensional transport regimes of Anderson localization as well as of diffusive transport. The detailed analysis of the temperature dependent data demonstrates that the local on-top nano-sized contacts do not induce significant strain to the epitaxial graphene films.
Direct Measurement of Surface Transport on a Bulk Topological Insulator
Lucas Barreto,Lisa Kühnemund,Frederik Edler,Christoph Tegenkamp,Jianli Mi,Martin Bremholm,Bo Brummerstedt Iversen,Christian Frydendahl,Marco Bianchi,Philip Hofmann
Physics , 2013, DOI: 10.1021/nl501489m
Abstract: Topological insulators are guaranteed to support metallic surface states on an insulating bulk, and one should thus expect that the electronic transport in these materials is dominated by the surfaces states. Alas, due to the high remaining bulk conductivity, surface contributions to transport have so-far only been singled out indirectly via quantum oscillations, or for devices based on gated and doped topological insulator thin films, a situation in which the surface carrier mobility could be limited by defect and interface scattering. Here we present the first direct measurement of surface-dominated conduction on an atomically clean surface of bulk-insulating Bi$_2$Te$_2$Se. Using nano-scale four point setups with variable contact distance, we show that the transport at 30 K is two-dimensional rather than three-dimensional and by combining these measurements with angle-resolved photoemission results from the same crystals, we find a surface state mobility of 390(30) cm$^{2}$V$^{-1}$s$^{-1}$ at 30 K at a carrier concentration of 8.71(7)$\times 10^{12}$ cm$^{-2}$.
Exceptional ballistic transport in epitaxial graphene nanoribbons
Jens Baringhaus,Ming Ruan,Frederik Edler,Antonio Tejeda,Muriel Sicot,Amina Taleb Ibrahimi,Zhigang Jiang,Edward Conrad,Claire Berger,Christoph Tegenkamp,Walt A. de Heer
Physics , 2013, DOI: 10.1038/nature12952
Abstract: Graphene electronics has motivated much of graphene science for the past decade. A primary goal was to develop high mobility semiconducting graphene with a band gap that is large enough for high performance applications. Graphene ribbons were thought to be semiconductors with these properties, however efforts to produce ribbons with useful bandgaps and high mobility has had limited success. We show here that high quality epitaxial graphene nanoribbons 40 nm in width, with annealed edges, grown on sidewall SiC are not semiconductors, but single channel room temperature ballistic conductors for lengths up to at least 16 micrometers. Mobilities exceeding one million corresponding to a sheet resistance below 1 Ohm have been observed, thereby surpassing two dimensional graphene by 3 orders of magnitude and theoretical predictions for perfect graphene by more than a factor of 10. The graphene ribbons behave as electronic waveguides or quantum dots. We show that transport in these ribbons is dominated by two components of the ground state transverse waveguide mode, one that is ballistic and temperature independent, and a second thermally activated component that appears to be ballistic at room temperature and insulating at cryogenic temperatures. At room temperature the resistance of both components abruptly increases with increasing length, one at a length of 160 nm and the other at 16 micrometers. These properties appear to be related to the lowest energy quantum states in the charge neutral ribbons. Since epitaxial graphene nanoribbons are readily produced by the thousands, their room temperature ballistic transport properties can be used in advanced nanoelectronics as well.
Fontes alternativas para uma história das ciências
Edler, Flavio;
História, Ciências, Saúde-Manguinhos , 1995, DOI: 10.1590/S0104-59701995000100008
Abstract: in this study we call attention to the importance of 'manguinhos' scientific collections, which preserve a major portion of the memory of scientific practice as developed by brazilian researchers in the field of biomedical sciences. we make use of these collections to approach some little-known aspects of scientific activity: the historical evaluation of forms of zoological classification and efforts at legitimating scientific practice.
Computational statistics and biometry: which discipline drives which?
Edler, Lutz
GMS Medizinische Informatik, Biometrie und Epidemiologie , 2005,
Abstract: A biometrician's work is defined through the biological or medical problem and the mathematical and statistical methods needed for its solution. This requires in most instances statistical data analysis and the use of methods of computational statistics. At first, it seems quite obvious that the computational needs of the biometric problem determine what has to be developed by the discipline of computational statistics. However, viewing the development of biometry and computational statistics in Germany for the past decades in more details reveals an interesting interaction between the activities of the German Region of the International Biometric Society and groups engaged in computational statistics within Germany. Exact methods of statistical inference and permutation tests, simulations and the use of the Bootstrap, and interactive graphical statistical methods are examples of this fruitful reciprocal benefit. This contribution examines therefore relationships between the historical development of biometry and computational statistics in Germany using as sources of information contributions to the scientific literature, presentations and sessions at scientific conferences on biometry and on computational statistics which influenced the development of both disciplines and exhibits a reciprocal dependency. The annual workshops organized on the Reisensburg now for more than 30 years are recognized as an outstanding factor of this interrelationship. This work aims at the definition of the present status of computational statistics in the German Region of the International Biometric Society and intends to guide and to foster the discussion of the future development of this discipline among biometricians.
Uma história de amor à psicanálise A love story of psychoanalysis
Sandra Edler
Psicologia Clínica , 2009, DOI: 10.1590/s0103-56652009000200014
Abstract:
Silet, os paradoxos da puls o de Freud a Lacan Silet, the paradoxes of drive from Freud to Lacan
Sandra Edler
Psicologia Clínica , 2006, DOI: 10.1590/s0103-56652006000100018
Abstract:
Feios, sujos e malvados sob medida: a utopia médica do biodeterminismo, S o Paulo (1920-1945)
Flavio Edler
Revista Latinoamericana de Psicopatologia Fundamental , 2011, DOI: 10.1590/s1415-47142011000300011
Abstract:
Pesquisa clínica e experimental no Brasil oitocentista: circula??o e controle do conhecimento em helmintologia médica
Edler, Flavio Coelho;
História, Ciências, Saúde-Manguinhos , 2010, DOI: 10.1590/S0104-59702010000300010
Abstract: the contributions of brazilian physicians to knowledge of diseases caused by parasitic worms, during the second half of the nineteenth century, had distinct effects on three epistemic communities: brazilian clinical anatomy, french medical geography, and the emerging field of medical parasitology. accepting the heterogeneity of both the systems for legitimizing scientific facts and the epistemological practices observed by each discipline, the text provides a specific cartography of the period's medical knowledge, revealing the lines of force shaping the three disciplinary fields. the focus on the circulation, control and validation of medical knowledge reveals strong controversies and complicated negotiations between different epistemic communities.
O debate em torno da medicina experimental no segundo reinado
Edler, Flavio Coelho;
História, Ciências, Saúde-Manguinhos , 1996, DOI: 10.1590/S0104-59701996000200005
Abstract: although brazil's twentieth century medicine was strong in the clinical tradition, this was no structural barrier to innovations from the realm of laboratory experiments, contrary to what some historians have argued. the broad debate over the rules of 'experimental methods' reveals a dimension of the struggle waged between proponents of rival medical theories, within a context where dissension among physicians threatened their scientific authority vis-à-vis that of other types of healers.
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