258 research outputs found
Suppression of ferromagnetism in CeSi_1.81 under temperature and pressure
We have studied the pressure dependence of the magnetization of single
crystalline CeSi_1.81. At ambient pressure ferromagnetism develops below T_C =
9.5 Below ~ 5 K an additional shoulder in low-field hysteresis loops and a
metamagnetic crossover around 4 T suggest the appearance of an additional
magnetic modulation to the ferromagnetic state. The suppression of the magnetic
order in CeSi_1.81 as function of temperature at ambient pressure and as
function of pressure at low temperature are in remarkable qualitative
agreement. The continuous suppression of the ordered moment at p ~ 13.1 kbar
suggests the existence of a ferromagnetic quantum critical point in this
material.Comment: 9 pages, 9 figures, to be published in Physical Review
Electronic disorder of P- and B-doped Si at the metal-insulator transition investigated by scanning tunnelling microscopy and electronic transport
The (111)-2 × 1 surface of in situ cleaved heavily P- or B-doped Si is investigated by scanning tunnelling microscopy and spectroscopy at room temperature and at low temperature. P atoms have been identified on different sites of the Si(111)-2 × 1 surface by their characteristic voltage-dependent contrast for positive as well as negative buckling of the π-bonded chains. The distributions of dopants per surface area and of nearest-neighbour distances are found to be in agreement with a random arrangement of dopants in Si up to doping levels well above the metal–insulator transition. In addition, P atoms have been identified by their depth-dependent contrast down to the third layer beneath the surface with a volume density in agreement with the bulk doping density. The random electronic disorder supports the view of an Anderson transition driven by disorder close to the critical concentration or critical uniaxial stress
Entwicklung, Erprobung, Umsetzung und Evaluation von Strategien in den Bereichen Tiergesundheit, Haltung, Fütterung, Management in der ökologischen Ferkelerzeugung
Die ökologische Ferkelerzeugung weist hinsichtlich Tiergesundheit, Leistungsfähigkeit und Wirtschaftlichkeit große Defizite auf. Die Ursachen sind komplex und betreffen u.a. Fütterung, Haltung und Hygiene. Für diese Bereiche sollten durch Exakt- und Praxisversuche Lösungsansätze entwickelt werden. Teilprojekte umfassten folgende Themen: Der Einfluss unterschiedlicher Raufutter in der Fütterung tragender Sauen, die Wirkung einer Inulinzugabe sowie vom Extrudieren von Ackerbohnen in Sauen- und Ferkelfutter, die Bewertung alternativer Desinfektionsverfahren, ein Vergleich von Einzelhaltung versus kombinierte Einzel- und Gruppenhaltung säugender Sauen sowie die Optimierung des Ferkelliegebereichs in der Ferkelaufzucht.
Zentrale Ergebnisse:
- Die verschiedenen Raufuttervarianten (Kleegrassilage, Heu, Maissilage, Topinamburknollen) hatten keine negativen Effekte auf Körperkonstitution und Reproduktionsleistungen der Sauen.
- Die Saugferkel der mit Inulin versorgten Sauen entwickelten sich gegenüber der Kontrollgruppe während der Säugezeit leistungsmäßig besser, während der Ferkelaufzucht gab es keine Leistungssteigerungen. Der Einsatz von getoasteten Ackerbohnen führte zu signifikant besseren Ferkelzunahmen gegenüber dem Einsatz von extrudierten Ackerbohnen.
- Keines der getesteten alternativen Desinfektionsverfahren (HeiĂźwasserdampf, elektroaktiviertes Wasser, Abflammen) ist eine Alternative zur chemischen Desinfektion bezĂĽglich Keimreduktion, Arbeitsaufwand und Kosten.
- Gruppensäugen führt bei Sauen zu erhöhter Aktivität sowie zu spezifischen Verhaltensanpassungen. Leistungseinbußen konnten weder für Sauen noch für Ferkel dokumentiert werden. „Gruppensäugen“ führt zu einem höheren Arbeitszeitbedarf und steigenden Baukosten.
- Der Liegebereich für Aufzuchtferkel ist in vielen Betrieben nicht optimal und durch z. T. einfache Maßnahmen (Abdichten des Liegenestes, Wärmedämmung des Bodens, Bodenheizung, Anbringen einer weiteren Wärmequelle) für die Tiere zu verbessern
Super Bloch oscillations in the Peyrard-Bishop-Holstein model
Recently, polarons in the Peyrard-Bishop-Holstein model under DC electric
fields were established to perform Bloch oscillations, provided the
charge-lattice coupling is not large. In this work, we study this model when
the charge is subjected to an applied field with both DC and AC components.
Similarly to what happens in the rigid lattice, we find that the carrier
undergoes a directed motion or coherent oscillations when the AC field is
resonant or detuned with respect to the Bloch frequency, respectively. The
electric density current and its Fourier spectrum are also studied to reveal
the frequencies involved in the polaron dynamics
Tunable magnetic properties of arrays of Fe(110) nanowires grown on kinetically-grooved W(110) self-organized templates
We report a detailed magnetic study of a new type of self-organized nanowires
disclosed briefly previously [B. Borca et al., Appl. Phys. Lett. 90, 142507
(2007)]. The templates, prepared on sapphire wafers in a kinetically-limited
regime, consist of uniaxially-grooved W(110) surfaces, with a lateral period
here tuned to 15nm. Fe deposition leads to the formation of (110) 7 nm-wide
wires located at the bottom of the grooves. The effect of capping layers (Mo,
Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was
studied. Significant discrepancies with figures known for thin flat films are
evidenced and discussed in terms of step anisotropy and strain-dependent
surface anisotropy. Demagnetizing coeffcients of cylinders with a triangular
isosceles cross-section have also been calculated, to estimate the contribution
of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the
interface element was used to tune the blocking temperature of the wires, here
from 50K to 200 K
Electronic structure and nesting-driven enhancement of the RKKY interaction at the magnetic ordering propagation vector in Gd2PdSi3 and Tb2PdSi3
We present first-time measurements of the Fermi surface and low-energy
electronic structure of intermetallic compounds Gd2PdSi3 and Tb2PdSi3 by means
of angle-resolved photoelectron spectroscopy (ARPES). Both materials possess a
flower-like Fermi surface consisting of an electron barrel at the G point
surrounded by spindle-shaped electron pockets originating from the same band.
The band bottom of both features lies at 0.5 eV below the Fermi level. From the
experimentally measured band structure, we estimate the momentum-dependent RKKY
coupling strength and demonstrate that it is peaked at the 1/2 GK wave vector.
Comparison with neutron diffraction data from the same crystals shows perfect
agreement of this vector with the propagation vector of the low-temperature
in-plane magnetic order, thereby demonstrating the decisive role of the Fermi
surface geometry in explaining the complex magnetically ordered ground state of
ternary rare earth silicides.Comment: 4 pages, 4 figure
MEDBERT.de: A Comprehensive German BERT Model for the Medical Domain
This paper presents medBERTde, a pre-trained German BERT model specifically
designed for the German medical domain. The model has been trained on a large
corpus of 4.7 Million German medical documents and has been shown to achieve
new state-of-the-art performance on eight different medical benchmarks covering
a wide range of disciplines and medical document types. In addition to
evaluating the overall performance of the model, this paper also conducts a
more in-depth analysis of its capabilities. We investigate the impact of data
deduplication on the model's performance, as well as the potential benefits of
using more efficient tokenization methods. Our results indicate that
domain-specific models such as medBERTde are particularly useful for longer
texts, and that deduplication of training data does not necessarily lead to
improved performance. Furthermore, we found that efficient tokenization plays
only a minor role in improving model performance, and attribute most of the
improved performance to the large amount of training data. To encourage further
research, the pre-trained model weights and new benchmarks based on
radiological data are made publicly available for use by the scientific
community.Comment: Keno K. Bressem and Jens-Michalis Papaioannou and Paul Grundmann
contributed equall
- …